CONCEPT PROJECT PROPOSAL: [Click HERE and type year]€¦ · Pomegranate fruit production is an emerging industry in South Africa. Currently, only about 6 cultivars are utilised for

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FINAL REPORT

1. PROGRAMME AND PROJECT LEADER INFORMATION

Principal Investigator’s Title, Initials, Surname

Prof. U.L. Opara

Present Position Distinguished Professor

Organisation, Department Stellenbosch University

Tel. / Cell no. 0218089242

E-mail [email protected]

2. PROJECT INFORMATION

PHI Project Number 12/2014

Project title Integrated postharvest innovative solutions for the South African pomegranate fruit sector

Fruit kind(s) Pomegranates

Start date (mm/yyyy) 01 January 2015 End date (mm/yyyy) 31 December 2016

Approved by Research Organisation Programme leader (tick box)

X

mailto:[email protected]

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THIS REPORT MUST INCLUDE INFORMATION FROM THE ENTIRE PROJECT

3. EXECUTIVE SUMMARY This must report on the ENTIRE project. Address the objectives and milestones of the project as well as the impact of the study on the industry, not exceeding 1000 words. You can overtype the example. NB: In addition, the Executive Summary may clearly capture

Objectives & Rationale To develop an integrated postharvest innovative solution for optimum fruit maturity, storage management and scientifically defined quality parameters of pomegranate fruit. Methods WP1: Pomegranate fruit (cvs. Acco, Herskowitz and Wonderful) grown in a commercial orchard in Wellington, South Africa (33.6333 oS, 18.9833 oE) were studied. The trees were five years old at a planting distance of 5 x 3 m. Pomegranate trees and fruit were tagged and fruit growth studies commenced at 28 days after full bloom and continued until commercial harvest during the 2015 / 2016 season. Changes in fruit mass, length are measured at 14-day intervals. Physicochemical properties of fruit from different commercial harvests were determined to identify the optimum maturity stage for long term storage (Milestone 1). Storage trials were performed after five fruit harvests from each cultivar, with the development of postharvest disorders tracked on a bi-weekly basis over six weeks. (Milestone 2). WP2: An array of pre-harvest physiological disorders was investigated before and during harvest periods (between February and April 2016) (Milestone 3). WP3: Cold chain performance of some of frequently used ventilated cartons and internal packages (liners) during forced-air cooling (FAC) and cold storage in the South African pomegranate industry, in terms of resistance to airflow (RTA), cooling characteristics, energy efficiency and fruit quality were investigated (Milestone 4). Key Results Based on combination of data on fruit physico-chemical properties, sensory analysis and incidence of storage disorders, the optimum harvest maturity coincided with 123-132 DAFB for ‘Acco’, 133-137 DAFB for ‘Herskowitz’ and >134 DAFB for ‘Wonderful’ pomegranate, respectively. (Milestone 1). ‘Herskowitz’ was most susceptible to postharvest crown rot during storage and shelf life, with higher incidence occurring in late harvested fruit (Milestone 2). All cultivars were susceptible to a wide range of pre-harvest fruit disorders and defects, with cracking only affecting ‘Herskowitz’ (Milestone 3). The results on packaging showed that packaging fruit inside a liner offered up to 50% greater resistance to air flow than fruit packaging with no liner. Consequently, the use of liners also delayed fruit cooling and increased energy consumption, with seven-eighths cooling times close to 3 times those of fruit inside packaging with no liner (Milestone 4). Conclusion/Discussion Appropriate harvest maturity indices were developed for three important commercial pomegranate cultivars grown in South Africa to ensure good eating quality and minimise storage losses after long supply chain handling and shelf life. Although 123-132 DAFB provides an appropriate window for commercial harvesting of ‘Acco’ pomegranate, it should be noted that fruit harvested after 127 DAFB are more susceptible to postharvest crown rot. (Milestone 1). Fruit quality disorders were tracked during fruit maturity development, with differences noted between cultivars (Milestone 3). The research multi-scale packaging of pomegranates has provided an insight into the effects of packaging design used in the pomegranate industry on cooling performance and impacts on fruit quality. Although the use of internal packaging (liners) minimised fruit weight loss, it increased RTA, precooling time, energy consumption and cooling costs (Milestone 4).

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This document is confidential and any unauthorised disclosure is prohibited Version 2016

4. PROBLEM IDENTIFICATION AND OBJECTIVES Pomegranate fruit production is an emerging industry in South Africa. Currently, only about 6 cultivars are utilised for commercial production. For the South African pomegranate industry to remain competitive in the global market, it is essential to develop science-based tools for the effective post-harvest quality management for these cultivars. Additionally, tools for indexing of postharvest disorders in the pomegranate fruit industry in South Africa remain a challenge, due to limited research done in this field. This affects processing options, packaging and marketability of the whole fruits in the overseas markets.

5. DETAILED REPORT Completion of a, b, c and d is compulsory.

a. PERFORMANCE CHART (for the duration of the project)

Milestone Target Date Extension

Date Date

completed

1. To develop predictive optimum maturity index for commercially grown pomegranate cultivars grown in South Africa.

30-12-2016

30-12-2016

2. To characterise storage potential and

shelf life for commercial pomegranate cultivars in consideration of the long supply chains.

30-06-2016 30-12-2016

3. Indexing and defining quality disorders of

SA grown pomegranates resulting in scientifically based quality standards for SA grown pomegranates.

30-06-2016 30-06-2016

4. Improve fruit cooling rate and quality by

optimizing multi-scale packaging of pomegranates

31-10-2016 31-10-2016

5. Journal publication(s) – final milestone (list intended Peer Reviewed and Popular/Semi-scientific publications. Completed publications to be listed in detail under point 6d)

31-12-2016

b) WORKPLAN (MATERIALS AND METHODS) The study was carried out during the 2015 / 2016 pomegranate season. Pomegranate fruit (cvs. Acco, Herskowitz and Wonderful) grown in a commercial orchard in Wellington, South Africa (33.6333 oS, 18.9833 oE) were studied. The trees were five years old at a planting distance of 5 x 3 m. Measurements of fruit length and width were done bi-weekly, from 28 to 132 days after full bloom (DAFB). Five fruit harvests were performed per cultivar; at DAFB 120, 123, 127, 132 and 136 for Acco; at DAFB 124, 128, 133, 137 and 141 for Herskowitz; and DAFB 134, 137, 140, 144 and 150 for Wonderful. Fruit from each harvest were stored at 5 oC for 6 weeks, followed by storage at 20 oC for 5 days to simulate shelf life conditions. To determine physico-chemical properties of juice, arils were extracted manually followed by extraction using a blender.

c) RESULTS AND DISCUSSION

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Work package 1: Predicting optimum maturity index and characterise nutritional significance Milestone 1: To develop predictive optimum maturity index for commercially grown pomegranate cultivars grown in South Africa M1A i) Growth

Preliminary results showed rapid increase in fruit length and diameter at the early stage of maturity for all cultivars. It is also noteworthy that the disparity between fruit length and diameter increased with increasing maturity because of more rapid increase in fruit diameter. This could be due to increase in fruit size because of increase in aril size, juice content, as well the development of the peel structure during fruit development. As expected, fruit weight increased with advancing days after full bloom in the three cultivars, and it followed a linear growth pattern like fruit length and diameter. Figures 1 – 3 show the changes in the length and width of Acco, Herskowitz and Wonderful. A total of 50 fruit; 5 fruit per tree, 10 trees per cultivar; were used to generate the growth curves.

30

40

50

60

70

80

90

20 40 60 80 100 120 140

Length Width Linear (Length) Linear (Width)

Dia

me

ter

(mm

)

Figure 1. Pomegranate cv Acco fruit growth curve from 28 – 140 days after full bloom

In all three growth curves, at 28 days after full bloom, the length and width of the fruit were similar. As the fruit progress through their developmental stages, the fruit width grows at a faster rate than the fruit length.

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Figure 2. Pomegranate cv Herskowitz fruit growth curve from 28 – 140 days after full bloom

30

40

50

60

70

80

90

20 40 60 80 100 120 140Length Width

Linear (Length) Linear (Width)

Figure 3. Pomegranate cv Wonderful fruit growth curve from 28 – 140 days after full bloom

The shape index is a measure of how a fruit approximates a sphere. A measure of 1 is a perfect sphere, with the length divided by the diameter equalling 1. The growth curves for the length and width of the fruit at different stages of growth and maturity permitted the tracking of changes in the shape index with time. The shape index is shown in Figure 4.

Dia

met

er

(mm

)

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0.85

0.9

0.95

1

28 49 70 91 112 133

Acco Herskowitz Wonderful

Days after full bloom

Figure 4. The change in shape index during the maturity and development of three commercial Pomegranate cultivars from 28 – 140 days after full bloom

The growth curves were used to demarcate the distinct maturity stages of each cultivar. The instrumental properties of Acco, Herskowitz and Wonderful at each maturity stage are documented in Table 1 below. The maturity stages for Acco are DAFB 28 – 48 (immature), 49 – 69 (mature-unripe), 70 – 97 (mature-mid-ripe), 98 – 112 (mature-ripe) and over 112 (mature-full-ripe). The maturity stages for Herskowitz and Wonderful are immature (28 – 69), mature-unripe (70 – 83), mature-mid-ripe (84 – 111), mature-ripe (112 – 125) and mature-full-ripe (over 126). The aril colour corresponding to the maturity stages of pomegranate cv. Wonderful are shown in Figure 3. Figure 4 – 6 shows the growth profiles of the three cultivars as they progressed from immature to mature-full-ripe growth stages. Table 1. Changes in chemistry during five maturity stages of three commercial pomegranate

cultivars.

Immature Mature-unripe Mature-mid-ripe Mature-ripe Mature-full-ripe

Weight (g) 85.1 + 0.6a 117.9 + 1.1b 172.1 + 2.1c 203.0 + 3.3d 220.9 + 3.5e

Acco TSS 10.2 + 0.8a 11.2 + 0.9a 12.7 + 0.4b 14.0 + 1.1c 13.0 + 0.6c

TA (%) 0.3 + 0.0a 0.5 + 0.0b 0.6 + 0.1b 0.8 + 0.1c 0.9 + 0.1c

Weight (g) 98.5 + 0.9a 134.2 + 1.8a 217.3 + 1.7a 267.1 + 2.2a 283.0 + 3.0e

Herskowitz TSS 9.0 + 0.2a 9.6 + 1.0a 10.9 + 1.9ab 12.2 + 0.9b 13.2 + 0.9c

TA (%) 1.5 + 0.3a 1.65 + 0.3a 1.78 + 0.3a 2.4 + 0.3b 2.5 + 0.6b

Weight (g) 115.7 + 1.7a 157.1 + 0.7b 222.1 + 2.5c 289.9 + 3.6d 302.1 + 3.7e

Wonderful TSS 9.9 + 0.4a 11.3 + 0.9b 11.8 + 0.7b 12.9 + 1.1bc 15.5 + 1.3c

TA (%) 1.9 + 0.0a 2.2 + 0.8b 2.2 + 0.9b 2.5 + 0.7b 2.7 + 0.2b

Figure 5 shows photographs of the distinct developmental stages of three commercial pomegranate cultivars. The figure shows that the external fruit peel colour does not correlate with the aril colour.

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Immature Mature-unripe Mature-mid-ripe Mature-ripe Mature-full-ripe

a) Acco

b) Herskowitz

c) Wonderful

Figure 5 Four developmental stages for the three commercial pomegranate cultivars.

Wonderful, a late harvest cultivar, maintained a green peel colour for a longer period during the developmental stages.

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Fruit was harvested at five harvest maturities (H1 – H5) and stored during the usual harvest season. Storage trials were performed after five fruit harvests from each cultivar, with the development of postharvest disorders tracked on a bi-weekly basis over six weeks. The development of postharvest disorders was investigated from each fruit harvest during the six-week storage at 5 oC, and 5-day shelf life at 20 oC. Figure 6 shows the incidence of crown rot, the sole postharvest disorder, after 6 weeks of storage and 5 days of shelf life.

0 10 20 30

Acco

Herskowitz

Wonderful

Incidence of crown rot (%)

Harvest 1 Harvest 2 Harvest 3

Harvest 4 Harvest 5

Figure 6 The incidence of postharvest crown rot after 6 weeks of storage at 5 oC and 5 days of shelf life at 20 oC

The incidence of crown rot was highest in Herskowitz, with 20 % of fruit from the 3rd and 4th harvests, as well as 30 % of fruit from the 5th harvest, exhibiting crown rot. While harvests 1 and 2 of Herskowitz were incidence free, all harvests of the Wonderful cultivar exhibited incidence of crown rot. However, the incidence was only 5 %. Acco exhibited incidence of crown rot in harvests 4 and 5, though the magnitude of incidence between the two harvests was substantial. Harvest 4 exhibited 5 % incidence, while harvest 5 exhibited 15 %.

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The sensory properties of Acco, Herskowitz are shown in figures 7 – 9. These radar plots show averaged sensory scores (scale = 0 – 5; n = 8) of pomegranate fruit at 5 different harvest times analysed after storage. Fruits were stored at 5 oC for 6 weeks and 5 – day shelf life period at 20 oC before sensory evaluation. H1 – 5 designates harvests 1 – 5. Figure 7 shows the sensory properties of Acco, with fruit from harvest 3 being both the sweetest and the sourest of the 5 harvests. Figure 10 shows harvest 3 as being the sweetest, and harvest 4 being the sourest of the five harvests.

Figure 7. Sensory properties of pomegranate cv Acco after 6 weeks of storage at 5 oC and 5 days of shelf life at 20 oC

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Figure 8. Sensory properties of pomegranate cv Herskowitz after 6 weeks of storage at 5 oC and 5 days of shelf life at 20 oC

The radar plot shown in Figure 9 represents Wonderful cultivar, with harvest 4 being the sweetest and harvest 5 being the sourest. The sweetness of the three pomegranate cultivars is related to the total soluble solids, an instrumentally measured property, with values represented graphically in Figure 10.

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Figure 9. Sensory properties of pomegranate cv Wonderful after 6 weeks of storage at 5 oC and 5 days of shelf life at 20 oC

At harvest 2, Herskowitz was shown to have the highest recorded TSS and Acco had the lowest. Furthermore, while the TSS values for Wonderful did not change much across the 5 harvests, the lowest TSS value for this cultivar was recorded at harvest 2.

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Figure 10. TSS values of three pomegranate cultivars at five different harvests after 6 weeks of storage at 5 oC and 5 days of shelf life at 20 oC

The initial large-scale loss of fruit may have caused the trees to send a stress response signal to the remaining fruits. The effects of the stress response on the production or depletion of fruit sugars is cultivar specific. Figure 11 shows the TA values of the three commercial pomegranate cultivars. The highest TA value for Acco (which was observed at harvest 4) was the same as the lowest TA value for Herskowitz (also observed at harvest 4). This value was the same as the lowest value for Wonderful (observed at harvest 1). An ideal balance which corresponds to a favourable taste, would be observed when the TSS value is high, and the TSS is low. The ratio if TSS to TA can be expressed using two terms; the TSS / TA and the BrimA ( = TSS - kTA, where k = 2 for South African pomegranates).

Figure 11. TA values of three pomegranate cultivars at five different harvests after 6 weeks of storage at 5 oC and 5 days of shelf life at 20 oC

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Figure 12. BrimA values of three pomegranate cultivars at five different harvests after 6 weeks of storage at 5 oC and 5 days of shelf life at 20 oC

BrimA is shown in Figure 12, while TSS / TA is shown in Figure 13. The BrimA for Wonderful is highest at Harvest 1, while it is at its lowest for Acco and Herskowitz. The highest BrimA for Acco was at Harvest 5, with the highest for Herskowitz being at harvest 2. The TSS / TA values give a different picture, with the highest Acco, Herskowitz and Wonderful values observed at Harvests 5, 4 and 1.

Figure 13. TSS / TA values of three pomegranate cultivars at five different harvests after 6 weeks of storage at 5 oC and 5 days of shelf life at 20 oC

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A discriminant analysis of the instrumental and sensory attributes of the three cultivars was performed to establish which attributes were the most significant at selecting the best harvests for each cultivar. Figures 14, 15 and 16 show the use of instrumental and sensory attributes to generate variables charts for the discriminant analysis of Acco, Herskowitz and Wonderful cultivars, respectively.

Figure 14. Variables chart for the discriminant analysis of Acco cultivar, using instrumental and sensory attributes. The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC and 5 days of shelf life at 20 oC

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Figure 14 shows the identification of TSS / TA, sour taste, hue (h), yellowness (b) and lightness (L) colorimetric properties as significant. This derivation is summarised in Table 2. However, it is important to note that b is not a useful parameter for pomegranate arils, as they are red in colour. Figure 15 showed BrimA, pH, L and TA to important discriminating variables for Herskowitz harvests, and this is summarised in table 3.

Figure 15. Variables chart for the discriminant analysis of Herskowitz cultivar, using instrumental and sensory attributes. The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC and 5 days of shelf life at 20 oC

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Figure 16 showed pH and aril colour to be useful variables in discriminating between harvests of Wonderful, with this information summarised in table 4.

Figure 16. Variables chart for the discriminant analysis of Wonderful cultivar, using instrumental and sensory attributes. The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC and 5 days of shelf life at 20 oC

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The terms used in the tables depicting the summary of the variables selections (tables 3, 7 and 11) are explained as follows: Partial R2 = determination coefficient, F static = F ratio test; F = P- value at significance level of 0.05. Table 2. Summary of the variables selection showing attributes of Acco cultivar that contribute most to the harvest group using a stepwise (forward) analysis. The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC and 5 days of shelf life at 20 oC

Cultivar Variable IN/OUT Status Partial R² F Pr > F

Acco b IN 0.897 75.974 < 0.0001

Sour IN 0.511 8.893 < 0.0001

h IN 0.507 8.476 < 0.0001

TSS/TA IN 0.416 5.688 0.001

L IN 0.265 2.798 0.043 Table 3. Summary of the variables selection showing attributes of Herskowitz cultivar that contribute most to the harvest group using a stepwise (forward) analysis The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC and 5 days of shelf life at 20 oC


Herskowitz L IN 0.997 2964.739 < 0.0001

BrimA IN 0.794 32.731 < 0.0001

pH IN 0.452 6.804 0.000

TA IN 0.390 5.119 0.003

b IN 0.292 3.192 0.026 Table 4. Summary of the variables selection showing attributes of Wonderful cultivar that contribute most to the harvest group using a stepwise (forward) analysis. The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC and 5 days of shelf life at 20 oC


Wonderful pH IN 0.433 6.676 0.000

Aril colour IN 0.316 3.932 0.010

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Tables 5, 6 and 7 show the variables and factors correlations of the discriminant analysis for the sensory and instrumental data for Acco, Herskowitz and Wonderful cultivars, respectively. Correlations was at P < 0.05. Values highlighted in bold indicate strong to moderate correlations between variables and their corresponding factors. Figures 7, 19 and 21 show the observation charts for the discriminant analysis of Acco Herskowitz and Wonderful cultivars, respectively, using instrumental and sensory attributes. Table 5. Variables and factors (F1 and F2) correlations of discriminant analysis for the sensory and instrumental data for Acco cultivar. The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC and 5 days of shelf life at 20 oC

F1 F2 F3 F4

Sweet

0.304 0.191 0.405 0.016

Sour

-0.176 0.184 0.822 -0.399

Astringency 0.003 -0.033 0.205 0.032

Crispness

0.106 -0.112 -0.063 0.087

Juiciness

-0.044 0.234 -0.206 -0.194

Grittiness

-0.295 -0.321 -0.202 0.021

Hardness

-0.021 0.138 -0.107 0.231

Aril colour

0.101 0.054 0.082 0.016

Appearance 0.178 -0.303 0.112 -0.111

Flavour

0.109 -0.226 0.070 0.007

Acceptability 0.421 0.218 0.064 -0.118

TSS

-0.395 -0.217 0.010 0.167

pH

-0.563 0.202 0.168 -0.045

TA

-0.096 0.620 -0.215 -0.580

TSS/TA

0.118 -0.762 0.197 0.591

BrimA

-0.229 -0.567 0.149 0.504

L

0.025 -0.341 -0.420 -0.079

a

0.928 0.135 0.233 -0.195

b

0.950 0.221 0.215 0.001

h

0.725 0.557 0.259 0.310

C 0.941 0.159 0.228 -0.140

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Table 6. Variables and factors (F1 and F2) correlations of discriminant analysis for the sensory and instrumental data for Herskowitz cultivar. The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC and 5 days of shelf life at 20 oC

F1 F2 F3 F4

Sweet

-0.200 0.081 -0.112 -0.299

Sour

0.267 -0.005 -0.108 0.124

Astringency -0.104 -0.012 -0.258 -0.137

Crispness

0.069 0.089 -0.007 0.173

Juiciness

-0.076 -0.021 0.231 0.042

Grittiness

-0.084 0.031 0.220 -0.200

Hardness

0.113 0.004 0.128 0.035

Aril colour

0.119 0.001 0.197 -0.132

Appearance 0.059 -0.263 -0.048 -0.124

Flavour

-0.157 0.097 -0.045 -0.328

Acceptability -0.055 -0.058 -0.014 -0.057

TSS

-0.322 0.792 0.495 -0.157

pH

0.017 0.642 -0.542 0.541

TA

0.107 -0.591 0.769 0.221

TSS/TA

-0.100 0.510 -0.720 0.066

BrimA

-0.311 0.921 0.028 -0.232

L

0.990 0.121 -0.027 0.067

a

0.254 0.099 0.233 -0.121

b

0.554 0.374 0.156 -0.072

h

0.415 0.350 -0.064 0.057

C 0.418 0.223 0.245 -0.123

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Table 7. Variables and factors (F1 and F2) correlations of discriminant analysis for the sensory and instrumental data for Wonderful cultivar. The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC and 5 days of shelf life at 20 oC

F1 F2

Sweet

-0.079 -0.091

Sour

0.000 0.140

Astringency 0.237 0.016

Crispness

-0.033 -0.016

Juiciness

0.018 -0.004

Grittiness

-0.022 -0.121

Hardness

0.112 -0.340

Aril colour

-0.435 0.900

Appearance 0.065 0.060

Flavour

0.000 -0.140

TSS

0.172 0.161

pH

0.913 0.409

TA

-0.603 0.101

TSS/TA

0.631 -0.097

BrimA

0.536 0.060

L

-0.189 -0.083

a

-0.230 0.149

b

-0.173 0.039

h

0.124 -0.214

C -0.219 0.125

Tables 8, 9 and 10 show the confusion matrixes showing the number of correct and incorrect predictions model made by the model compared to the actual classifications in the instrumental and sensory data of Acco, Herskowitz and Wonderful, respectively. The Discriminant analysis models predicted 92.5 % (for Acco), 100 % 9 for Herskowitz) and 40 % (for Wonderful) of the fruit falling into 5 classes, based on the 5 harvests. Confusion was observed in Acco between harvests 1 and 2, and harvests 2 and 3. No confusion was observed in Herskowitz, while confusion was observed between all five harvests of Wonderful.

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Table 8. Confusion matrix showing the number of correct and incorrect predictions model made by the model compared with the actual classifications in the instrumental and sensory data for Acco cultivar The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC and 5 days of shelf life at 20 oC

from \ to H1 H2 H3 H4 H5 Total %

correct

H1 8 0 0 0 0 8 100.00%

H2 0 7 1 0 0 8 87.50%

H3 0 1 6 1 0 8 75.00%

H4 0 0 0 8 0 8 100.00%

H5 0 0 0 0 8 8 100.00%

Total 8 8 7 9 8 40 92.50%

Table 9. Confusion matrix showing the number of correct and incorrect predictions model made by the model compared with the actual classifications in the instrumental and sensory data for Herskowitz cultivar The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC and 5 days of shelf life at 20 oC

from \ to H1 H2 H3 H4 H5 Total %

correct

H1 8 0 0 0 0 8 100.00%

H2 0 8 0 0 0 8 100.00%

H3 0 0 8 0 0 8 100.00%

H4 0 0 0 8 0 8 100.00%

H5 0 0 0 0 8 8 100.00%

Total 8 8 8 8 8 40 100.00%

Table 10. Confusion matrix showing the number of correct and incorrect predictions model made by the model compared with the actual classifications in the instrumental and sensory data for Wonderful cultivar The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC and 5 days of shelf life at 20 oC

from \ to H1 H2 H3 H4 H5 Total % correct

H1 6 0 2 0 0 8 75.00%

H2 2 0 5 0 1 8 0.00%

H3 1 0 5 0 2 8 62.50%

H4 2 0 0 2 4 8 25.00%

H5 0 0 3 2 3 8 37.50%

Total 11 0 15 4 10 40 40.00%

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The confusion matrixes are consistent with the observation plots of Acco (Figures 7) Herskowitz (Figure 19) and Wonderful (Figure 21). Acco harvests clustered into three groups, group 1 (harvest 1), group 2 (harvests 2, 3 and 4) and group 3 (harvest 5).

Figure 17. Observations chart for the discriminant analysis of Acco cultivar, using instrumental and sensory attributes. The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC and 5 days of shelf life at 20 oC H1 – H5 designated harvest times 1 – 5.

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Herskowitz harvests were sufficiently different so as to have none of the harvests clustering with one another.

Figure 18. Observations chart for the discriminant analysis of Herskowitz cultivar, using instrumental and sensory attributes. The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC and 5 days of shelf life at 20 oC H1 – H5 designated harvest times 1 – 5.

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Based on how the observations were clustered, all five Wonderful harvests were sufficiently similar, with no discrimination.

Figure 19. Observations chart for the discriminant analysis of Wonderful cultivar, using instrumental and sensory attributes. The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC and 5 days of shelf life at 20 oC H1 – H5 designated harvest times 1 – 5.

Tables 11, 12 and 13 summarised the Pearson correlation coefficients among key instrumental attributes of Acco, Herskowitz and Wonderful cultivars, respectively, at shelf life. The relationships with correlation coefficients > 0.5 were presented. Values highlighted in bold represent strong (>0.75) correlations.

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Table 11. Pearson correlation coefficients among key instrumental attributes of Acco cultivar at shelf life. The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC and 5 days of shelf life at 20 oC

Chemical properties r

TSS/ TA TA

-0.887

BrimA

0.736

BrimA TSS

0.756

TA

-0.672

Colorimetric properties r

b a

0.966

h

0.869

C

0.983

h C

0.789

C a 0.997

Table 12. Pearson correlation coefficients among key instrumental attributes of Herskowitz cultivar at shelf life.. The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC and 5 days of shelf life at 20 oC

Sensory attributes r

Sweet Overall flavour 0.883

Hardness Acceptability -0.565


BrimA TSS

0.88

TA

-0.607

pH TSS / TA

0.752

TA

-0.675

TA TSS / TA

-0.851


L b

0.585

b h

0.606

C 0.712

Table 13. Pearson correlation coefficients among key instrumental attributes of Wonderful cultivar at shelf life. The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC and 5 days of shelf life at 20 oC .

Sensory attributes r

Sour Overall flavour -1


pH TA

-0.509

TSS / TA

0.536

BrimA

0.514


C L

0.576

a

0.994

b

0.944

b L

0.557

a

0.904

a L 0.57

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The discriminant analysis of the five harvests, comparisons of key instrumental attributes as well as Pearson correlation coefficients were considered to derive the maturity index of the three cultivars, shown in table 14. This index was proposed in consideration of which harvests exhibit crown rot during storage and shelf life. Table 14 shows narrow windows of harvest for Acco (123 – 132 days after full bloom) and

Herskowitz (133 -137 DAFB). These windows are necessary to ensure that the quality attributes

of the fruits are maintained for the duration of storage during shipping as well as shelf life.

Table 14. A summary of the maturity index of three commercial pomegranate cultivars

Cultivar DAFB TSS TA TSS / TA BrimA

Acco 123 – 132 12.5 - 14.0 0.6 - 1.1 33 - 35 11.0 - 13.0

Herskowitz 133 – 137 12.9 - 15.8 1.4 - 1.5 6 - 12 10.8 - 11.2

Wonderful >134 >15.0 1.0 - 1.6 >13 >11.0

Key results for milestone 1

All three pomegranate fruit cultivars followed a linear growth pattern over the study

period (28-133 DAFB)

Characteristic fruit shapes developed around 110 DAFB for all three cultivars studied

Fruit skin colour was not a good indicator of aril colour during fruit growth and maturation

Sugar concentration (TSS) fluctuated during fruit growth and maturation, particularly for

‘Herskowitz’ and ‘Acco’

All cultivars were susceptible to a wide range of preharvest fruit disorders and defects,

but cracking affected only ‘Herskowitz’

‘Herskowitz’ was most susceptible to crown rot, with higher incidence occurring during

later harvest

Based on combination of data on fruit physico-chemical properties, sensory analysis and

incidence of storage disorders, the optimum harvest maturity coincided with 123-132

DAFB for ‘Acco’, 133-137 DAFB for ‘Herskowitz’ and >134 DAFB for ‘Wonderful’

pomegranate, respectively.

Opara 27


Milestone 2 : To characterise storage potential and shelf life for commercial pomegranate cultivars in consideration of the long supply chains. The storage potential and shelf life of the three cultivars was determined. Each cultivar was harvested at five harvest maturities (H1 – H5) and stored during the usual harvest season. Storage trials were performed after five fruit harvests from each cultivar, with the changes in chemical attributes, appearance and the incidence of postharvest disorders tracked on a bi-weekly basis over six weeks. The six-week storage period was at 5 oC. Table 1 – 3 shows the changes in chemical attributes during storage and shelf life, with week 0 representing the baseline. The differences between the harvest chemical attributes appear to be more significant than the differences attributed to storage for 6 weeks. Table 1. The chemical attributes of Acco. The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC. The letters indicate significant difference (p > 0.05)

Acco TSS pH TA TSS/TA BrimA

Harvest 1 Week 0 13.0b 2.4a 0.9b 14.4ab 11.2a

Harvest 1 Week 2 13.3b 3.4bc 0.5a 26.6d 12.3ab

Harvest 1 Week 4 13.4b 2.4a 0.6a 22.3c 12.2ab

Harvest 1 Week 6 13.4b 3.0 0.5a 26.8 12.4ab

Harvest 2 Week 0 12.5a 3.0b 0.75b 16.7b 11.0a

Harvest 2 Week 2 12.2a 2.9b 0.7b 17.5b 10.8a

Harvest 2 Week 4 12.9ab 2.9b 0.9b 14.3ab 11.1a

Harvest 2 Week 6 12.9ab 3.1b 0.6a 24.8 13.7b

Harvest 3 Week 0 13.4b 3.0b 0.4a 33.5e 12.6ab

Harvest 3 Week 2 13.4b 3.6c 0.4a 33.5e 12.6ab

Harvest 3 Week 4 13.7bc 3.3bc 0.6a 24.5b 13.5b

Harvest 3 Week 6 13.1b 3.1b 0.5a 26.2d 12.1ab

Harvest 4 Week 0 14.0c 3.6b 1.5c 9.3a 11.0a

Harvest 4 Week 2 14.2c 2.8b 1.1b 12.9a 12.0ab

Harvest 4 Week 4 14.0c 3.3bc 1.3b 10.8a 11.4a

Harvest 4 Week 6 14.5cd 3.2bc 1.2b 12.1a 12.1ab

Harvest 5 Week 0 14.6cd 3.2bc 1.2b 12.6a 12.3ab

Harvest 5 Week 2 14.5cd 3.3bc 0.6a 24.2c 13.3b

Harvest 5 Week 4 14.9d 3.2bc 0.9b 17.7b 14.1bc

Harvest 5 Week 6 14.7d 3.3bc 0.7b 22.4c 14.3bc

The TSS / TA values for all five harvests of Acco generally show a gradual increase with prolonged storage. However, for Herskowitz, shown in table 2, harvest 5 shows a decrease in TSS / TA as the fruit is stored. This may be due to an increase in TA values from week 0 to week 6.

Opara 28


Table 2. The chemical attributes of Herskowitz. The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC. The letters indicate significant difference (p > 0.05)

Herskowitz TSS pH TA TSS/TA BrimA

Harvest 1 Week 0 13.2a 2.9b 2.5b 5.3a 8.2a

Harvest 1 Week 2 13.3a 2.4a 2.2b 6.2a 9.0a

Harvest 1 Week 4 13.6a 2.9b 2.2b 6.1a 9.2a

Harvest 1 Week 6 13.7a 3.1c 1.6a 8.7ab 10.5b

Harvest 2 Week 0 14.5b 2.9b 1.4a 10.4b 11.7b

Harvest 2 Week 2 15.0bc 3.2c 1.6a 9.6b 11.9b

Harvest 2 Week 4 15.2c 3.3c 1.4a 10.9b 12.4b

Harvest 2 Week 6 14.8b 2.8b 1.6a 9.1b 11.6b

Harvest 3 Week 0 15.2c 3.0b 1.4a 10.8b 12.4b





Harvest 4 Week 2 14.4b 3.5c 1.5a 9.3b 11.3b





Harvest 5 Week 4 15.9c 2.4a 1.7a 8.2ab 10.4b

Harvest 5 Week 6 15.7c 3.2c 1.8a 7.2a 9.3a

The TSS values of Wonderful, shown in table 3, appear to fluctuate between a range of 13 - 15 oBrix. This fluctuation is shown in the TSS / TA as well as in the BrimA values.

Opara 29


Table 3. The chemical attributes of Wonderful. The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC. The letters indicate significant difference (p > 0.05)

Wonderful TSS pH TA TSS/TA BrimA

Harvest 1 Week 0 15.5c 2.3a 1.3a 11.9a 12.9c

Harvest 1 Week 2 15.2c 2.8a 1.1a 14.5b 13.1c

Harvest 1 Week 4 13.8b 2.8a 1.3a 10.6a 11.2b



Harvest 2 Week 2 14.7bc 4.0 1.1a 13.4b 12.5b

Harvest 2 Week 4 14.1b 3.8b 1.4a 10.1a 11.3b

Harvest 2 Week 6 15.6c 3.3b 1.3a 11.6a 12.9c

Harvest 3 Week 0 13.6b 2.9a 1.2b 11.3a 11.2b

Harvest 3 Week 2 13.1ab 3.0b 1.3a 10.1a 10.5b


Harvest 3 Week 6 14.7bc 3.3b 1.5a 9.8a 11.7b

Harvest 4 Week 0 11.9a 4.0c 1.4a 8.4a 9.1a



Harvest 4 Week 6 16.1c 3.1b 1.5a 10.7a 13.1c

Harvest 5 Week 0 14.7bc 3.2b 1.8a 8.4a 11.2b



Harvest 5 Week 6 14.0b 3.0b 1.6a 8.8a 10.8a

Tables 1 – 3 show the changes in chemical attributes with storage. However, the greatest determining factor of storage is the propensity to be susceptible to postharvest disorders. Fruit with retained flavour is of no use if it exhibits disorders such as crown rot, as there are concerns that such disorders may spread easily from infected to uninfected fruit. Figure 1 shows the incidence of postharvest crown rot disorder in three commercial pomegranate cultivars; Acco (a), Herskowitz (b) and Wonderful (c). Five harvest per cultivar were stored for 6 weeks, with the occurrence of postharvest disorder observed every three weeks. For Acco and Heskowitz, no crown rot was observed in fruit from the first 2 harvests. Herskowitz harvest 3 showed crown rot incidence at week 4, while both Acco and Herskowitz showed crown rot incidence in weeks 4 and 6. Harvest 5 of Herskowitz exhibited crown rot incidence in the second week of storage. With Wonderful, all 5 harvests exhibited mild crown rot in the sixth week of storage, while harvest 5 fruit exhibited crown rot incidence as early as the fourth week. Based on these observations of postharvest disorder development, the first three harvests of Acco and the first two harvests of Herskowitz would be ideal, as no crown rot incidence was observed. The first four harvests of Wonderful exhibit mild crown rot in the sixth week of storage. Therefore, it would be advisable to harvest the fruit as early as is possible.

Opara 30


a) Acco

0

5

10

15

20

25

30

Harvest 1 Harvest 2 Harvest 3 Harvest 4 Harvest 5

Week 0 Week 2 Week 4 Week 6

Cro

wn

ro

t in

cid

en

ce %

b) Herskowitz

0

5

10

15

20

25

30



Cro

wn r

ot in

cid

ence %

b) Wonderful

0

5

10

15

20

25

30



Cro

wn

ro

tIn

cid

en

ce %

Figure 1. Incidence of postharvest crown rot disorder in three commercial pomegranate cultivars. The pomegranate cultivar was harvested at five different periods, with each harvest stored for 6 weeks at 5 oC and 5 days of shelf life at 20 oC

The key result for milestone 2

Susceptibility to postharvest crown rot during storage is harvest dependant for Acco and Herskowitz

Although all harvests are equally susceptible, the incidence in Wonderful is much lower than in Acco or Herskowitz.

Opara 31


Work package 2: Identification and indexing of severity of pre-harvest disorders affecting export (postharvest) quality of three commercial pomegranate fruit cultivars

Milestone 3: Indexing and defining quality disorders of SA grown pomegranates resulting in scientifically based quality standards for SA grown pomegranates The study progressed from 28 days after full bloom until during commercial harvest between Feb – April 2016 depending on cultivar. An array of pre-harvest physiological disorders was investigated. The study focused on common disorders that compromised fruit quality standards such as sunburn/bleaching, cooking disorder (where fruit arils are cooked on the inside), bruising and cracking. Figure 1 shows photographs of pre-harvest disorders.

a) b)

c) d)

e)

Figure 1. Photographs of observed pre-harvest disorders. a = cracking, b = abrasions, c = false codling moth, d = sunburn, e = scald

shows the incidence of pre-harvest disorders, while figure 2 shows the severity, as expressed by the severity index. This index is calculated by multiplying the scores of severity (severity scores; 1 = trace, 2 = slight, 3 = moderate, 4 = severe, 5 = extremely severe) by the fruit affected and dividing by the total number of fruit. The results show that cracking was limited to Herskowitz. In addition, the proportion of fruit affected by disorders differed between cultivars, with sunburn and superficial scald more pronounced in Wonderful, a late-stage maturing cultivar.

Opara 32


0

5

10

15

20

25

Sunburn Abrasion Scald Cracking False Codling Moth

Immature Mature-unripe Mature-midripe Mature-ripe

Pro

port

ion o

f fr

uit

harb

ouring

fruit

dis

ord

ers

(%

)

a) Acco

b) Herskowitz

c) Wonderful

Figure 1. Proportion of three commercial pomegranate cultivars harbouring fruit disorders during four maturity stages

No severity score was given for false codling moth infestation, as any evidence of false codling moth attack is considered extremely severe. Figure 2 shows that Wonderful is severely affected by sunburn. This may be due to the fact that Wonderful is a late harvest cultivar.

Opara 33


0

0.1

0.2

0.3

0.4

0.5

Sunburn Abrasion Scald Cracking

Acco Herskowtiz WonderfulS

eve

rity

in

de

x

a) Mature-unripe

b) Mature-mid-ripe

c) Mature ripe / Mature-full-ripe

Figure 2. Severity of pomegranate fruit disorders during the fruit maturity stages

Key result for milestone 3

The incidence and severity of pre-harvest disorders in commercial pomegranates is cultivar specific.

Opara 34


Work package 3: Multi-scale packaging approach and optimisation of modified atmosphere packaging (Milestone 4) Milestone 4: Improve fruit cooling rate and quality by optimizing multi-scale packaging of pomegranates The overall aim of this study (M4) was to evaluate the cold chain performance of some of frequently used ventilated cartons and internal packages (liners) during forced-air cooling (FAC) and cold storage in the South African pomegranate industry, in terms of resistance to airflow (RTA), cooling characteristics, energy efficiency and fruit quality. Table 1 Studied pomegranate cartons used in the South African pomegranate industry and their ventilations

Carton Carton orientation

Wall area (m2)

Vent area (m2)

Ventilation (%)

Lengthwise Widthwise Top Bottom Total

0.046 0.035 0.116 0.116 0.313

0.003 0.001 0.064 0.004 0.072

6.52 2.86 55.17 3.45 23.00

Lengthwise Widthwise Top Bottom Total

0.034 0.030 0.093 0.093 0.25

0.003 0.002 0.064 0.002 0.071

8.82 6.67 68.82 2.15 28.4

CT1

CT2

Opara 35


Table 2 Photographs of studied cartons showing ventilation of all carton orientations

Carton

Orientation

Widthwise Lengthwise Top Bottom

CT1

CT2

The performance of two ventilated corrugated fibreboard carton designs (referred to as CT1 and CT2 in this study) with fruit bulk inside liner versus no liner was studied during forced-air cooling (FAC). Resistance to airflow (RTA), energy consumption and fruit cooling characteristics of stacked cartons were investigated. The study entailed air being forced through the 1.2 m side of stack (lengthwise orientation) and through the 1.0 m side of stack (widthwise orientation) (Figure 2). The two studied carton designs had 5.4% difference in total ventilation (CT1 – 23% and CT2 – 28.4%) (Tables 1 & 2; Figure 1).

Opara 36


Figure 1 Diagram of packaging combinations and stages of the pomegranate fruit for RTA, energy consumption and cooling experiments. No-liner packaging E has fruit sitting (on tray for CT1) at the bottom of the carton; liner packaging F has a liner enclosing the fruit (and tray); and stack G is sitting on a standard pallet of dimensions 1.2 x 1.0 m.

Opara 37


Figure 2 Pallet stacks of studied carton designs showing the stack orientations and total stack ventilation (TSV) and side view sketch of experimental set up inside cold room.

CT2 had relatively higher ventilation lengthwise and widthwise, 8.82% and 6.67%, respectively, compared to that of CT1 (6.52% and 2.86%) (Table 1). This resulted into a generally faster cooling rate (29.6%) for fruit packaged in CT2, but, over 3 times higher RTA in CT2 compared to CT1 stacks due to vent-hole obstruction during stacking of CT2 in the lengthwise orientation of stack as shown in the Figures 3 – 5. The results also showed that liner packaged fruit (reference) in CT1 and CT2 on average offered 53.00% and 50.23% greater resistance to airflow (RTA) than fruit packaged with no liner, respectively.

Opara 38


Figure 3 CT1 stack seven-eighths cooling time as a function of the package components, stack level and stack orientation: A = Lengthwise orientation; and B = widthwise orientation. Different letters indicate significance difference (p<0.05).

Figure 4 CT2 stack seven-eighths cooling time as a function of the package components, stack level and stack orientation: A = Lengthwise orientation; and B = widthwise orientation. Different letters indicate significance difference (p<0.05).

Opara 39


Figure 5 CT1 stack seven-eighths cooling time as a function of package components, fruit position in a stack level and stack orientation: A = Lengthwise orientation; and B = Widthwise orientation. Different letters indicate significance difference (p<0.05).

Figure 6. CT2 stack seven-eighths cooling time as a function of package components, fruit position in a stack level and stack orientation: A = Lengthwise orientation and B = widthwise orientation. Different letters indicate significance difference (p<0.05).

Opara 40


50

100

150

200

250

300

350

400

450P

ress

ure

dro

p (

Pam

-1)

Empty; lengthwise

Liner; lengthwise

Liner; widthwise

No liner; widthwise

No liner; lengthwise

Empty; widthwise

A

0

100

200

300

400

500

600

0.0 0.1 0.2 0.3 0.4 0.5 0.6

Pre

ssu

re d

rop

(P

am-1

)

Superficial air velocity (ms-1)

Empty; lengthwise

No liner; widthwise

No liner; lengthwise

Liner; widthwise

Liner; lengthwise

Empty; widthwise

B

Figure 7. Pressure drop as a function of packaging components and orientation of stack during forced-air cooling of pomegranates: A = CT1 stack and B = CT2 stack.

Opara 41


In comparison to empty CT1 cartons, liner packaging (reference) resulted in 62.81% and 72.64% higher RTA compared to 23.76% and 39.84% of no-liner packaging (reference) in the lengthwise and widthwise orientations of stack, respectively. The lengthwise orientation of CT1 stack had a surface total vent area of 6.35% compared to 4.24% for the widthwise orientation which may be the reason for the comparatively lower RTA lengthwise. On the contrary, CT2 stack had a larger ventilation of 8.57% in the widthwise orientation compared to 2.35% lengthwise. The low stack ventilation lengthwise was due to vent-hole obstruction during stacking. Fruit packaged with no liner in CT1 stack cooled 61.21% faster than liner packaged fruit (reference) with average seven-eighths cooling times (SECT) of 4.5 hours and 11.6 hours, respectively. Liner packaging and stack orientation significantly affected cooling of fruit in CT2 stack, resulting in about 64.29% faster cooling rate with no liners, and 10.00% faster cooling in the widthwise stack orientation. Fruit in liner upstream the stack (at the entrance of cold air) cooled about 16.67% and 23.08% faster than the fruit in the middle and at the back layers within the same stack level, respectively, for both carton designs as shown in Figure 7A&B. Stack ventilation and packaging design also affected the energy requirements for cooling fruit. CT1 stack, with liner packaging in the lengthwise orientation of stack, had the highest energy consumption (208.38±6.85 MJ) during precooling while widthwise orientation with no-liner packaging of the same carton design (which had the highest ventilation) resulted in lower energy requirement (2.48±0.15 MJ) to precool fruit. The energy requirement to precool fruit in the CT2 stack in the lengthwise orientation was over 10 times higher than the widthwise orientation due to vent-hole obstruction in the stack lengthwise. Furthermore, precooling fruit with CT2 required over 2 and 4 times more refrigeration energy using no liner and liner inside the packaging, respectively, compared to CT1 carton design. The two studied carton designs, CT1 and CT2 had 5.4% difference in total ventilation. CT2 had relatively higher ventilation in both length and width directions (8.82% and 6.67%, respectively) compared to CT1 (6.52% and 2.86%). In a stack of cartons packed with fresh pomegranate fruit (cv. Wonderful), this resulted into a generally faster fruit cooling rate (29.19%) in CT2. However, the obstruction of vent-holes in the lengthwise orientation of the stack of CT2 resulted in over 50% higher RTA compared to CT1. The results also showed that packaging fruit inside a liner offered up to 50% greater RTA than fruit packaging with no liner. Consequently, the use of liners also delayed fruit cooling and increased energy consumption, with seven-eighths cooling times close to 3 times those of fruit inside packaging with no liner. Packaging fruit with liner required about 3.9 and 8.7 times more energy to cool fruit in CT1 and CT2, respectively, compared with no-liner. During FAC of fruit over a period of 11.6 and 4.5 hours in liner and no liner, respectively, the use of humidification to maintain 95±1% relative humidity (RH) minimised weight loss by about 13.63% compared to precooling fruit inside cold room at 90±1% RH. Fruit packaged without liners also lost about 17.39% more weight during precooling compared to fruit packaged with liners (Figure 9). Significantly high weight loss up to 29.13±1.49% at day 30 was observed in fruit stored at low RH compared to 5.78±0.44% at high RH. In addition, liner packaged precooled fruit lost weight in equal magnitude to fruit under humidified precooling (0.19±0.003%). At the end of a 30 day storage period, this magnitude of fruit weight loss was estimated to be worth about ZAR7.78/kg and ZAR1.54/kg under low and high RH conditions, respectively. Fruit stored under low RH were also severely shrivelled and reduced in size. The high RH environment better maintained fruit colour, texture and chemical quality attributes (Figure 10; Table 3).

Opara 42


Figure 8. Fan energy requirement to achieve seven-eighths cooling time as a function of internal packaging, stack orientation and volumetric flow rate through CT1 stack, A; CT2 carton B; and C = combination of CT1 and CT2 graphs.

Opara 43


Figure 9. Pomegranate fruit weight loss as a function of cold room humidification, packaging and fruit position in a stack level during precooling. Vertical bars denote the standard error of the mean. Different letters indicate significance difference (p>0.05).

Table 2 Changes chemical attributes of pomegranate fruit (cv. Wonderful) stored at low (65±6.79%) and high (95±1.23%) RH at 20oC for 30 days

Storage duration

(days) RH TSS (ºBrix) TA (% Citric Acid) pH TSS:TA

0 15.24±0.50g 1.76±0.13bc 3.65±0.06a 9.36±1.12a-e

9 Low 16.50±0.28ab 1.91±0.13a-c 3.32±0.03bc 8.94±0.56b-e

High 15.40±0.17e-g 1.78±0.15bc 3.32±0.04bc 9.65±1.12a

21 Low 16.54±0.25ab 2.30±0.16a 3.16±0.04b-d 7.36±0.45a-d

High 15.67±0.38b-g 1.78±0.13bc 3.36±0.04bc 9.33±0.71a-e

30 Low 16.72±0.24a-c 2.33±0.22a 3.08±0.04ef 7.80±0.78c-e

High 15.71±0.24d-g 1.78±0.14bc 3.25±0.05b-d 9.40±0.86a-e

Opara 44


Figure 10 Pictorial presentation of the changes in appearance of pomegranate at 20ºC at the studied RH con ditions (Low = 65±6.79%; High = 95±1.23%).

Key results of milestone 4

This research has provided an insight into the cooling performance and impacts on fruit quality using some of the packaging designs used in industry for commercial handling of pomegranates.

This information is of help in making package design decisions and handling at pack-houses.

Additionally, an insight into moisture loss properties of pomegranate fruit and how this relates to the prevailing RH was generated

Opara 45


d) CONCLUSIONS In summary, South African pomegranates are produced for the export market, with the supply chain being key to maintaining the commercial viability of this crop. This study aimed to develop tools and techniques to minimise postharvest fruit loss. This involved 1) The development of a predictive optimum maturity index for commercially grown pomegranate cultivars grown in South Africa. 2)The characterisation of the storage potential and shelf life for commercial pomegranate cultivars in consideration of the long supply chains. 3)Indexing and defining quality disorders of SA grown pomegranates resulting in scientifically based quality standards for SA grown pomegranates. 4)Improvement of fruit cooling rate and quality by optimizing multi-scale packaging of pomegranates A summary of the key results is as follows:

All three pomegranate fruit cultivars followed a linear growth pattern over the study

period (28-133 DAFB)

Characteristic fruit shapes developed around 110 DAFB for all three cultivars studied

Fruit skin colour was not a good indicator of aril colour during fruit growth and maturation

The incidence and severity of pre-harvest disorders in commercial pomegranates is

cultivar specific.

Sugar concentration (TSS) fluctuated during fruit growth and maturation, particularly for

‘Herskowitz’ and ‘Acco’

All cultivars were susceptible to a wide range of preharvest fruit disorders and defects,

but cracking affected only ‘Herskowitz’

Susceptibility to postharvest crown rot during storage is harvest dependant for Acco and

Herskowitz

Although all harvests are equally susceptible, the incidence in Wonderful is much lower

than in Acco or Herskowitz.

‘Herskowitz’ was most susceptible to crown rot, with higher incidence occurring during

later harvest

Based on combination of data on fruit physico-chemical properties, sensory analysis and

incidence of storage disorders, the optimum harvest maturity coincided with 123-132

DAFB for ‘Acco’, 133-137 DAFB for ‘Herskowitz’ and >134 DAFB for ‘Wonderful’

pomegranate, respectively.

This research has provided an insight into the cooling performance and impacts on fruit

quality using some of the packaging designs used in industry for commercial handling of

pomegranates.

This information is of help in making package design decisions and handling at pack-

houses.

Additionally, an insight into moisture loss properties of pomegranate fruit and how this

relates to the prevailing RH was generated

Opara 46


This study proposes the ideal quality attributes for three cultivars, in consideration of their long term storage and shelf life. Furthermore, this study showed how cold room humidification was a potential remedy to extreme moisture loss and maintenance of fruit quality while achieving faster cooling. Given the high cost of energy for precooling fruit, improved understanding of the effects of delay in precooling on fruit quality after long term cold storage is warranted. There is also need for analysing the effect of humidification on the mechanical integrity of the fibreboard cartons.

6. ACCUMULATED OUTPUTS • December 2015: postgraduate seminar presentation at Food Science Department • August 2016: Postharvest Workshop at Stellenbosch University

a) TECHNOLOGY, KNOWLEDGE PRODUCTS AND PATENTS DEVELOPED None

b) TECHNOLOGY & KNOWLEDGE PRODUCTS TRANSFER None

c) HUMAN RESOURCES DEVELOPMENT/TRAINING

Student Name and Surname

Student Nationality Degree (e.g. MSc Agric, MComm)

Level of studies in final year of

project Graduation date

Honours students

Megan van Rensburg South African BSc(hons) Agric 1 March 2017

Thea Genis South African BSc(hons) Agric 1 March 2017

Faith Mokapane South African BSc(hons) Agric 1 March 2017

David Fisher Zimbabwean BSc(hons) Agric 1 March 2017

Masters Students

Matia Mukama Ugandan MSc Agric 2 March 2016

PhD students

Postdocs

William Mavengere Zimbabwean Postdoc 2

d) PUBLICATIONS (POPULAR, PRESS RELEASES, SEMI-SCIENTIFIC, SCIENTIFIC)

Opara 47


e) PRESENTATIONS/PAPERS DELIVERED Fawole, O.A. and Opara, U.L. (2016) Development of optimum fruit maturity and scientifically

defined quality parameters of pomegranate fruit. Presentation at Combined congress at University of the Free State, Bloemfontein, 18 - 21 January 2016.

Fawole O.A., Mavengere W.N. and Opara U.L. (2016) Integrated postharvest innovative

solutions for the South African pomegranate fruit sector. Oral presentation at the Postharvest Innovation Symposium at Stellenbosch, 21 – 22 November, 2016

Mavengere W.N., Fawole O.A., Opara U.L. (2016) Developing harvest maturity index for

commercial pomegranate fruit cultivars in South Africa, Poster presentation at the Postharvest Innovation Symposium at Stellenbosch, 21 – 22 November, 2016

Mukama M., Tsige A. and Opara U.L. (2016) Resistance to airflow, energy consumption and

fruit cooling rates inside different packaging designs used for handling pomegranates in South Africa, Poster presentation at the Postharvest Innovation Symposium at Stellenbosch, 21 – 22 November, 2016

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CONCEPT PROJECT PROPOSAL: [Click HERE and type year]€¦ · Pomegranate fruit production is an emerging industry in South Africa. Currently, only about 6 cultivars are utilised for