Quality and handling shelf life of macadamia styles and quality - mark penter

Optimisation of Kernel Storage Parameters and the Prediction of Shelf

Life for South African Macadamia Kernel

M.G. Penter, F.J. Kruger and A.D. Sippel

Agricultural Research Council - Institute for Tropical and Subtropical Crops P/Bag X11208, Nelspruit, 1200, South Africa

South African Industry Export value for 2011

$ 103 660 000 R850 000 000

Slide Compliments of Rudolf Badenhorst

Background


Background


Background

SA Macadamia Tree Age Distribution (%)

18.8

36.3

31.5

13.4

0 - 5 yrs

6 - 10 yrs

> 11 yrs

Unknown

Slide Compliments of Andrew Sheard

Background

2012 2017 2022

34 500 t 41 800 t 50 000 t ?

Slide Compliments of Derek Donkin

Background

Introduction

• Consequences of rapid industry growth include:

– NIH spending longer periods on the ground

– NIS being held on farm for longer periods

– NIS being held longer at processors

– Extended harvesting season (‘Beaumont’)

– Processed kernel being held for longer periods

Introduction

• Industry needs information:

–Extended shelf life (optimised storage)

–Accurate sell-by dates

–Export kernel required to have peroxide <

3meq/kg

Quality parameters

• Peroxide

• Breakdown products of peroxides

Peroxide production

Factors promoting peroxide formation

• Oxygen

• Lipoxygenases

• Light

• Metals (iron, manganese, copper)

• Water

• Heat

• Time (maturity, NIS holding period)

• Oil exposure to oxygen

Storage trials

• Procure commercially packed kernel (nitrogen flushed, vacuum packed, 5.68kg)

• Examine the effect of: – Storage period

– Storage temperature

– Style

– Seasonality

• Use peroxide analysis to monitor quality (react with iodide, titrate iodine with Na2S2O3)

Early season

-5C 5C 15C

RT

6, 12, 18, 24 months

0, 2, 4, 6, 8, 12, 16, 20 weeks on shelf

Peroxide analysis

Mid season

-5C 5C 15C

RT

6, 12, 18, 24 months

0, 2, 4, 6, 8, 12, 16, 20 weeks on shelf

Peroxide analysis

Late season

-5C 5C 15C

RT

6, 12, 18, 24 months

0, 2, 4, 6, 8, 12, 16, 20 weeks on shelf

Peroxide analysis

0

2

4

6

8

10

12

14

E 6m 0w E 6m 2w E 6m 4w E 6m 6w E 6m 8w E 6m 12w E 6m 16w E 6m 20w

Pe

roxi

de

val

ue

(m

eq

/kg)

Early season kernel stored 6 months

-5˚C S1 -5˚C S5 5˚C S1 5˚C S5 15˚C S1 15˚C S5 Ambient S1 Ambient S5

0

2

4

6

8

10

12

14

M 6m 0w M 6m 2w M 6m 4w M 6m 6w M 6m 8w M 6m 13w M 6m 16w M 6m 20w

Pe

roxi

de

val

ue

(m

eq

/kg)

Mid season kernel stored 6 months


0

2

4

6

8

10

12

14


Pe

roxi

de

val

ue

(m

eq

/kg)



0.24 0.12 0.12 0.12 12.83 0.12

0

2

4

6

8

10

12

14

L 6m 0w L 6m 2w L 6m 5w L 6m 8w L 6m 12w L 6m 20w

Pe

roxi

de

val

ue

(m

eq

/kg)

Late season kernel stored 6 months


0

2

4

6

8

10

12

14

L 6m 0w L 6m 2w L 6m 5w L 6m 8w L 6m 12w L 6m 20w

Pe

roxi

de

val

ue

(m

eq

/kg)



0.25 7.14 0.87 0.12 5.12 7.60

2..51

9.73

0.25

0.37

3.25

7.99

For kernel stored 6 months

• Ambient temperature not sufficient for late season kernel – requires storage temperatures of 15˚C or less

• Data variability is of concern – arises from small quantities of poor kernel in otherwise good batches

0

2

4

6

8

10

12

14

E 12m 0w E 12m 2w E 12m 4w E 12m 6w E 12m 8w E 12m 12w E 12m 16w E 12m 20w

Pe

roxi

de

val

ue

(m

eq

/kg)



0

2

4

6

8

10

12

14


Pero

xid

e v

alu

e (

meq

/kg

) Mid season kernel stored 12 months


0

2

4

6

8

10

12

14

16

L 12m 0w L 12m 2w L 12m 4w L 12m 6w L 12m 8w L 12m 12w L 12m 16w L 12m 20w

Pe

roxi

de

val

ue

(m

eq

/kg)




• Style 5 is of concern, particularly at ambient temperatures

• Late season style 5 at all temperatures except -5˚C approach 3meq/kg after 5 months on the shelf

• Style 5 to be consumed within 3 months of repacking or held below 0˚C if longer shelf life is required

• Mid season kernel appears to be of better quality than early or late season kernel

0

2

4

6

8

10

12

E 18m 0w E 18m 2w E 18m 5w E 18m 8w E 18m 12w E 18m 16w E 18m 20w

Pe

roxi

de

val

ue

(m

eq

/kg)


-5C S1 -5C S5 5C S1 5C S5 15C S1 15C S5 Ambient S1 Ambient S5

0

2

4

6

8

10

12

M 18m 0w M 18m 2w M 18m 4w M 18m 6w M 18m 8w M 18m 12w

M 18m 16w

M 18m 20w

Pe

roxi

de

val

ue

(m

eq

/kg)



0

2

4

6

8

10

12

L 18m 0w L 18m 2w L 18m 4w L 18m 6w L 18m 8w L 18m 12w L 18m 16w L 18m 20w

Pe

roxi

de

val

ue

(m

eq

/kg)




• Style 5 again cannot be held at ambient temperature – not even for mid season harvest

• For both style 1 and 5, 15˚C is inadequate for storing late season kernel if 5 months shelf life is required in retail packs

Predicting shelf life

Rancimat

• Also known as:

– Swift test

– Accelerated oxidation test

• Principle:

– At elevated temperatures and oxygen levels, poor samples with existing oxidative damage will degrade rapidly

0

5

10

15

20

25

30

35

40

45

50

Style 1 Style 5 Style 1 Style 5 Style 1 Style 5

Early season Mid season Late season

Ind

ucti

on

peri

od

(h

ou

rs)

Style and harvest timing

Effect of style and harvest time on Rancimat induction period

Rancimat

• The rancimat test predicts:

– Kernel quality and shelf life declines as season progresses

– Style 5 has lower storage potential than style 1

• Is this prediction accurate?

Conclusions

• Style 5 kernel has lower storage potential than style 1 kernel (assume this applies to all styles with fractured kernel

• For vacuum packed bulk kernel: – For storage periods of up to 12 months, ambient

temperature is not suitable

– For storage periods of 18 months temperatures of 15˚C may not be adequate

Conclusions

• Kernel quality declines as season progresses and there may be small quantities of poor kernel in early season batches – Is there old kernel picked up in the early season?

– Is late season kernel spending longer on the orchard floor / drying bins?

• Rancimat may be able to predict shelf life – further work required to correlate induction times and shelf life

Thank You

• SAMAC

• ARC

• Bioservices cc

• Elvis Nkwana and Yvonne Nxundu

Technology

Quality and handling shelf life of macadamia styles and quality - mark penter