CHARACTERISTICS OF PORK WITH DOCOSAHEXAENOIC ACID SUPPLEMENTED IN TEE DIET

N.G. MARRIOTr".', J.E. GARRETT', M.D. SIMS', H.WANG1 and J.R. ABRIL2

'Department of Food Science & Technology Virginia Polytechnic Institute & State University

Blacksburg, VA 24061-0418

'Omega Tech, Inc. 4909 Nautilus Court North Boulder, CO 80301-3242

'Virginia Scientific Research, Inc. 1866 East Market Srreer Harrisonburg. VA 22801

Received for Publication March 28,2002 Accepted for Publication May 22,2002

ABSTRACT

The omega-3 fatty acid, docosahexaenoic acid (DHA) was added to the basal diet of market pigs at 0, 0.125 and 0.250 kg/pig for 22-42 days. There were three consecutive pens per block with 10 blocks for a total of 30pens assigned to each treatment group. No diferences were found in off-flavor, juiciness, and overall flavor of the semimembranosus muscle and cured bacon among the three treatment groups. Furthermore, weight loss during storage and cooking did not differ among the three treatments. Objective evaluation results for oxidative rancidity did not difer between hams from control pigs and those from pigs receiving 0.250 kg/pig DHA. Shear force of cured bacon did not diffkr among the three treatments. These data suggest that DHA, when fed at 0.125 and 0.250 kg/pig, causes no adverse effects on carcass characteristics, sensory attributes, and tenderness of market size pigs.

4Corresponding Author

Journal of Muscle Foods 13 (2002) 253-263. AN Rights Reserved. "Copyright 2002 by Food & Nutrition Press, Inc.. Trumbull. Connecticut. 253

254 N.G. MARRIOTT, J.E. GARRETT, M.D. SIMS. H. WANG and J.R. ABRlL

INTRODUCTION

During the past decade, health conscious consumers have expressed interest in increased consumption of omega-3 fatty acids because of the potential advantages for the reduction of heart disease. Although various omega-3 fatty acids occur in the flesh of terrestrial meat animals and to a larger degree in aquatic life, it seems logical to evaluate the potential of adding these lipid components to the diet of terrestrial meat animals in an attempt to concentrate omega-3 fatty acids in these muscle foods, especially the long chain docosahexaenoic acid (DHA).

Research has been conducted (Wood and Enser 1997) to determine the influence of fatty acids in meat and the role of antioxidants in improving meat quality. In all species, fatty acid composition can be altered via the diet, albeit more easily in monogastic animals and birds where the linoleic, a-linolenic, aid long-chain polyunsaturated fatty acid content responds quickly to increased dietary concentrations (Van Elswyk 1993). Wood and Enser (1997) indicated that feeding pigs higher levels of a-linolenic acid or products such as DHA present in fish oils produce different flavors (including fishy flavors) in cooked pork due to the different oxidative changes during storage and cooking. These authors recognized that these off flavors can be prevented with high dietary levels of the antioxidant, vitamin E.

Leskanich et al. (1997) reported that the level of n-3 (omega-3) polyunsaturates were significantly increased in the tissues from pigs fed diets with associated alterations in n-6 to n-3 fatty acid ratios. These scientists and Rhee et al. (1 990b) found that diet manipulation with these fatty acids did not affect carcass characteristics, lean color, or sensory traits of fresh chops and sausages. These results support earlier research conducted (Rhee et al. 1990a; St. John et al. 1987) which concluded that monounsaturated fatty acid content can be elevated substantially in pork without adversely influencing the meat quality, thus producing a product perceived to be more healthful by the consumer.

Docosahexaenoic acid is part of the omega-3 polyunsaturated fatty acid family. It is a long chain omega-3 fatty acid (22:6) and is the most unsaturated fatty acid occUring in nature. A natural source of DHA is the marine mkroalgae. This algae exists in nature and is the form that is utilized by cold water fatty fish which have high DHA concentrations in their flesh.

A limited amount of research on the feeding of DHA in the form of marine microalgae to meat animals and poultry has been conducted. Sims et al. (2000b) found that turkey hens and toms were not adversely affected by feeding up to 20 g of DHA per kg of body weight based on their similar weight gain, feed efficiency, and carcass characteristics. However, breast samples of tom turkeys fed 10 g of DHA per kg of live weight developed more off aroma, and rancid flavor than those without this supplement. These investigators found no differences in TBARS values among the treated and untreated birds.

PORK WITH DOCOSAHEXAENOIC ACID 255

In a similar study with chlckens that were fed DHA, Sims et al. (2000a) found no differences in live performance traits and carcass characteristics. Their results revealed that the presence of omega-3 fatty acids in breast and thigh meat is detectable by sensory evaluation with a linear relationship to both dose and storage time. However, no differences in TBARS values were found among the treated and untreated samples. Furthermore, Lopez-Ferrer et al. (2001) reported that feeding long-chain polyunsaturated fatty acids to broiler chickens had an insignificant effect on carcass yield or quality parameters. Szymczyk et al. (2001) reported similar results when conjugated linoleic acid isomers were fed to broilers.

Limited research has been conducted to evaluate the affect of DHA on pork carcass characteristics. Therefore, this study was conducted to evaluate the effects of two levels of DHA supplemented into the diet of market pigs on carcass characteristics and palatability traits.

MATERIALS AND METHODS

Prior to the start of this study, all experimental pigs purchased from a mid- Atlantic auction with an unknown genetic background, were weighed and allocated to pens so that all animals within a block of three pens were of similar weight. This arrangement was achieved by placing the pigs in ascending pen number order by ascending weight order. Each group had an equal number of pigs assigned to each treatment group. Starting weight was approximately 65 kg and average weight gain per pig during this study was ca 40 kg.

Study Design

Study design and methods were incorporated to control bias. There were three consecutive pens per block with 10 blocks for a total of 30 pens. The 30 pens were randomly assigned to each treatment group.

Observation group number 1 received nonsupplemented corn-soybean oil meal based feed. The pigs in observation group number 2 were provided 0.625 kg of a commercial preparation of DHA (DHA Gold T‘, Omega Tech, Inc., Boulder, Colo.), which was produced by a closed tank “yeast like” fermentation process of the single cell microalgae schizochytrium sp. (Barclay et al. 1994), over 42 days at a rate of 85% for 0-21 days and 15% for 22-42 days. DHA was mixed into the diet that was fed from 0-21 days at the rate of 4.6 kg/910 kg of feed such that 85% of the 0.625 kg of DHA was consumed in 68 kg of feed. From 22-42 days, 0.81 kg/9 10 kg of feed of the same commercial preparation of DHA was incorporated to achieve 85% of the 0.625 kg was consumed in 16.8 kg of feed.

The pigs in observation group 3 were provided 1.25 kg of the same commercial preparation of DHA as group 2 over 42 days at a rate of 85% for 0-21 days and 15% for 22-42 days. DHA was mixed into the diet fed from 0-21 days at the rate

256 N.G. MARRIOTT, J.E. GARRETT, M.D. SIMS,H. WANG and J.R. ABNL

of 9.21 kg/910 kg of feed such that 85% of 1.25 kg of DHAwas consumed in 68 kg of feed. From 22-42 days, DHA was mixed into the diet at the rate of 1.63 kg/910 kg such that 85% of the 1.25 kg of DHA was consumed in 68 kg of feed.

Harvesting Process

The pigs were electrically stunned, exsanguinated, scalded, dehaired, eviscerated, and split at the Virginia Polytechtuc Institute & State University Meats Laboratory according to industry standards, then chilled to 4C within 24 h.

Carcass Evaluation

The pork carcasses were fabricated into wholesale cuts according to Savell and Smith (2000). Carcass data were obtained from seven pigs from treatment 1 (control), nine from treatment 2 (0.125 kg/pig), and eight from treatment 3 (0.250 kg/pig) 24 h postmortem. These selections were based on similarity of live weights at 44 days withm each treatment. In addition to preslaughter weight, hot carcass weight, and muscle weight (fat trimmed to 6.35 mm thickness) and fat trim was recorded for the muscles of the boneless shoulder, boneless loin (longissimus muscle), ham (semimembranosus muscle), and belly. These cuts were vacuum packaged, labeled according to treatment, and stored at 2C until evaluation.

Sensory and Rancidity Evaluations

The pork samples to be evaluated were dry roasted to an internal temperature of 71C in a 165C heated Blodgett oven (GCS Source, Inc., Richmond, Va.) according to AMSA guidelines (AMSA 1995). Cooked samples were cooled to approximately 25C (ambient temperature). A sensory panel (five males and two females) trained over a 2-week period (AMSA 1995) evaluated the longissimus and semimembranosus muscles of each carcass and the cured (Savell and Smith 2000) belly with the use of a rating scale devised by Marriott (2001). Sensory evaluations included off flavor @=none; l=very intense), juiciness (8~xtremely juicy; l=extremely dry), and overall flavor @=extremely desirable favor; 1 =extremely undesirable flavor).

Oxidative rancidity as measured by thiobarbituric acid reactive substances (TBARS), was conducted according to the procedure devised by Tarladgis et al. ( 1960) for the longissimus, semimdranosus, boneless shoulder, and cured belly after 1, 14,36, and 50 days postmortem storage under vacuum at 2C. Tenderness of bacon slices (3.0 mm thick) was measured objectively for peak force (kg) and energy ( k g - d m m ) by a Wamer-Bratzler shear device attached to a computer interfaced Instron (Model 101 1, Instron C o p , Canton Mass.) Equipped with a 50 kg load cell with a crosshead speed of 200 mmlmin, 10% load range, and modified to measure the force required to penetrate a slice of uncooked bacon.

PORK WITH WCOSAHEXAENOIC ACID 257

Storage Loss and Cook Loss

Percentage package purge and cook loss were determined for the samples that were cooked for sensory evaluation. Storage loss was percentage of purge in the package after storage and was calculated based on the difference between whole package weight and bag weight. Cooking loss values were calculated based on the weight of the samples before and after cookmg.

Statistical Analysis

Data were analyzed using the General Linear Model procedures of SAS (Statistical Analysis Systems Institute, Inc. 2000). A completely randomized block design with three treatments was used for the three consecutive pens per block of the 10 blocks. When si@icance (P< 0.05) was determined, means were separated using the Least Significant Difference Test (SAS 2000).

RESULTS AND DISCUSSION

Carcass Characteristics

Since no interactions occurred between dietary treatment and storage time for any of the measurements and storage time did not affect the observed traits, discussion will focus on dietary treatment. No dlfferences in preslaughter weight, hot carcass weight, or dressing percentage existed (Data not shown). These data reflect the uniformity of live weight and hot carcass weight and indicated that DHA supplementation into the diet had no effect (f30.05) on dressing percentage. These results are similar to those reported by Fontanillas et al. ( 1997) and Rhee et af. (1 990a) who indicated that the feeding of omega-3 fatty acids to pigs had no effect (DO.05) on either carcass or meat characteristics.

Percentage lean yield of boneless shoulders, trimmed bellies, and longissirnus and semimembranosus muscles did not differ (f30.05) among any of the dietary treatments (Tables 1-4). These results, which suggest that the supplementation of omega-3 fatty acids does not affect the muscle to fat ratio, are in agreement with those reported by St. John et af. (1987) and Leskanich ef al. (1997).

Purge and Cooking Loss

The addition of DHA to the diet of market pigs had no effect (-0.05) on cooking loss during storage of any of the samples during cooking (Tables 1-3). The longissimus samples with 0.125 kg/pig of DHA sustained less (Pc0.05) package weight loss during storage. Thls observation could be attributable only to

258 N.G. MARRIOTT, J.E. GARRETT, M.D. SIMS, H. WANG and J.R. ABRIL

Trait

experimental variation since the other samples did not differ ( m . 0 5 ) in weight loss during storage.

kg of DHAVpig ----- 0 0.125 0.250 SE

TABLE 1. TREATMENT EFFECTS ON SENSORY SCORES, TBARS, AND COOKING LOSS OF

PORCINE SEMIMEMBRANOSUS MUSCLE (ACROSS STORAGE EFFECTS)

Storage Loss (%)

Cook LOSS (Yo)

TBAW (mg/kg)

11.8' 10.8' 1O.P 0.927

28.5' 27.6' 29.4' 0.463

2.72' 2.36' 2.77' 0.08 1

I I I I

Sensory I I I 1 Off Flavor 6.4P 6.54' 0.063

Juiciness 6.1 1' 6.08' 6.18' 0.072

Overall Flavor 6.16' 6.43' 0.078

These results are similar to those reported by Miller et al. (1 990) who found no differences (M.05) in thaw loss, cooking loss, or total weight loss of pork chops from pigs fed elevated levels of monounsaturated fats. Rhee et al. (1990b) further supported these observations through their reporting that the addition of monounsaturated fats to the diet of market pigs had no (M.05) adverse effect on cooking loss and sensory properties.

Sensory Traits

The addtion of DHA to the diet of market pigs had no effect (DO.05) at either concentration (across storage times) on any of the sensory traits of the semimembranosus muscle or the cured bellies (bacon) (Tables 1 and 3). Furthermore, juiciness scores (Table 2) were not affected (m.05) by this omega-3 fatty acid. However, differences in overall flavor (P<O.OS) were found between control samples and those from pigs fed 0.125 kg/pig of DHA, even though no differences were detected between the longissimus samples from pigs fed 0.250 kg DHA and those without supplementation of this fatty acid. This observation can be best explained through experimental variation and that the

PORK WITH DOCOSAHEXAENOIC ACID 259

observed numerical deviations were less than 0.30 which suggests that the differences may not be a practical.

TABLE 2. TREATMENT EFFECTS ON SENSORY SCORES,

TBARS, AND COOKING LOSS OF PORCINE LONGISSIMUS MUSCLE (ACROSS STORAGE EFFECTS)

' Docosahexaenoic acid 'a.b Means bearing unlike letters within the same column differ (-0.05)

These data suggest that the effects of DHA on pork sensory traits are minimal. These results are similar to St. John et at. (1 987) who found that monounsaturated fatty acid content of pork can increase via dietary supplementation without adverse effects on meat quality. Research reported by Miller et al. (1990) does not fully support our results or those of Leskanich et al. (1997) who found that pigs fed canola oil had lower flavor scores and palatability evaluations and concluded that this treatment was an unacceptable method for increasing oleic acid levels in pigs, even though other oils such as safflower, and sunflower increases oleic acid and decreases palmitic acid content of lipid adipose deposits in longissimus muscle.

260 N.G. MARRIOTT, J.E. GARFWlT, M.D. SIMS, H. WANG and J.R. ABRlL

TABLE 3. TREATMENT EFFECTS ON SENSORY TRAITS, TEIARS, AND

COOKING LOSS OF BACON (ACROSS STORAGE EFFECTS)

I Docosahexaenoic acid hb Means bearing unlike letters within the same column differ (-0.05)

SE

0.141

0.181

0.160

1.733

0.088

Rancidity Development

Rancidity development over time in the semimembranosus and longissimus muscle, as measured by TBARS, was not affected (M.05) by DHA (Tables 1 and 2). The boneless shoulder and bacon samples manufactured from pigs fed 0.250 kg/pig of DHA had higher (R0.05) TBARS values than from pigs fed 0.125 kg (Tables 3 and 4). However, the "BARS values of boneless shoulders and bacon from pigs fed 0.250 kg of DHA did not differ (M.05) from that of pigs that were not fed DHA even though all of the values were high enough to impact sensory traits. Storage time from 1-50 days and had no effect ( lW.05) on TBARS (data not shown). It was demonstrated that DHA had a minimal effect on the development of oxidation rancidity. These results compare to those reported by Miller et al. (1993) which revealed that sausages prepared from pigs fed 10% of animal fat, saMower oil, or sunflower oil did not differ (130.05) in terms of the resulting TBA values. An explanation of the high TBARS values and high sensory scores is not obvious. Although some oxidation may have occurred during storage, it was not apparently severe enough to have an adverse effect on the sensory panel response.

PORK WITH WCOSAHEXAENOIC ACID 261

Trait

TBARS(mg/kg)

* kg of DHA'/pig

0 0.125 0.250 SE

0.148 2.49b 2.69b 3.38'

Bacon Characteristics

kg of DHAVpig

Trait 1 2 3 SE Insrron Force --

Peak force (kg) 7.13' 6.57' 7.25' 0.553

Energy ( k g - d m m ) 3.56' 3.43' 3.63' 0.270 c

Instron shear force as measured by peak force (kg) and energy (kg-mm/mm) revealed that DHA had no effect (m.05) on the force required to penetrate a slice of uncooked bacon (Table 5) . Thus, an increase of DHA does not appear to have an adverse on the tenderness and firmness of bacon.

262 N.G. MARRIOTT, J.E. GARRETT, M.D. SIMS, H. WANG and J.R. ABRIL

CONCLUSIONS

These data suggest that DHA fed at 0.125 and 0.250 kg/pig causes no adverse affects on carcass characteristics, sensory traits, oxidative rancidity, or shear force of cured bacon in market size commercial pigs. Therefore, pork tissue modification through the addition of DHA to the diet of market pigs offers consumers a product that may be perceived as being more healthful through the control of saturated fat in the diet.

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