PRODUCTION, MODELING, AND EDUCATION Research Notes

PRODUCTION, MODELING, AND EDUCATION Research Notes Sensory evaluation and consumer acceptance of eggs from hens fed flax seed and 2 different antioxidants Z. Hayat,* G. Cherian, 1 T. N. Pasha,* F. M. Khattak,* and M. A. Jabbar * * University of Veterinary and Animal Sciences, Lahore, 54000, Pakistan; University College of Agriculture, University of Sargodha, 40100, Pakistan; and Department of Animal Sciences, Oregon State University, Corvallis 97331 ABSTRACT The sensory attributes and consumer acceptance of eggs from flax seed-fed hens were evaluated by trained and untrained panelists. Hens were fed diets containing 0% flax seed (control), 10% flax seed (flax), 10% flax seed + 100 IU/kg of vitamin E (flax + α-tocopherol), or 10% flax seed + 100 mg/kg of butylated hydroxytoluene (BHT) (flax + BHT). Fresh eggs collected within 24 h were hard-boiled, coded, and were offered to trained panelists in 4 testing sessions. Sensory traits evaluated were aroma, flavor, off-flavor, and overall difference. The trained panelists rated flax, flax + α-tocopherol, and flax + BHT eggs to be different from control eggs (P < 0.001). In a second study, sensory attributes were tested by untrained panelists. The majority (75 to 80%) of the panelists could not distinguish flax seed-fed versus control eggs for aroma and flavor. A consumer preference test was also conducted to gauge end-user response to flax seed-fed eggs. Consumer acceptance testing did not find any significant difference (P > 0.05) between control and flax seed-fed eggs. These results suggest that flax seed when incorporated at 10% in the layer diet can produce eggs that are acceptable to untrained panelists and consumers. However, trained panelists are able to detect differences in flavor, aroma, and off-flavor and overall difference in eggs from hens fed flax seed. Antioxidant supplementation (vitamin E, BHT) did not enhance the acceptability of flax seed-fed eggs by trained panelists. Key words: egg, flax, sensory, vitamin E, butylated hydroxytoluene INTRODUCTION 2010 Poultry Science Association Inc. Received November 24, 2009. Accepted May 10, 2010. 1 Corresponding author: Gita.Cherian@oregonstate.edu 2010 Poultry Science 89 :2293 2298 doi: 10.3382/ps.2009-00575 The enrichment of eggs with n-3 fatty acids such as α-linolenic (18:3n-3), eicosapentaenoic (20:5n-3), docosapentaenoic (22:5n-3), and docosahexaenoic acid (22:6n-3) through the hen s diet is well documented (Leskanich and Noble, 1997; Van Elswyk, 1997; Gonzalez-Esquerra and Leeson, 2000; Cherian, 2008). The current practice of producing n-3 fatty acid-enriched eggs is achieved primarily by feeding flax seeds that are rich in α-linolenic acid to laying hens. Enrichment of eggs with n-3 fatty acids perpetuates the extent of fatty acid unsaturation, leading to oxidative damage of yolk lipids and overall reduction in egg quality, leading to lower preference scores (Jiang et al., 1991; López-Ferrer et al., 1999). Caston et al. (1994) reported a general perception by taste panelists that eggs from flax seedfed birds had a slight off-flavor. Flavor is consistently rated as the most important factor that determines consumption, the length of time food stays in the market, and repeat purchase (American Dietetic Association, 2000; Cardello et al., 2007). Therefore, to maintain egg quality, sensory attributes, and fatty acid stability, it is essential to prevent or minimize lipid oxidation. Antioxidants are generally added to the hens diet to minimize lipid oxidation and to enhance consumer acceptance of n-3 fatty acid-enriched eggs (Qi and Sim, 1998; Galobart et al., 2001). Both synthetic and natural antioxidants are frequently used in the food industry to prevent oxidation of lipids. Due to the limited number of antioxidants available, the major challenge for the food or feed industry is to use existing antioxidants more efficiently. The effect of natural antioxidants such as tocopherols on lipid oxidation products in n-3 fatty acid-enriched eggs has been reported by several authors (Wahle et al., 1993; Cherian et al., 1996; Leeson et al., 1998). However, the effects of natural versus synthetic antioxidants on egg organoleptic aspects are not known. Sensory or organoleptic attributes are usually evaluated in studies conducted on eggs enriched with bioactive components. Conventional sensory studies are 2293

2294 often done either with trained or untrained panelists to score eggs with respect to organoleptic characteristics. Sensory attributes such as aroma, flavor, aftertaste, and overall acceptability of eggs enriched with n-3 eggs are very important to consumers. The present study was conducted to evaluate the sensory aspects and consumer acceptance of eggs from hens fed flax seed with or without antioxidants. The first experiment was a trained taste panel analysis conducted to determine sensory differences among regular (control, no flax seed) eggs or those obtained from hens fed diets containing 10% flax seed or 10% flax seed with 2 types of antioxidants, natural (α-tocopherol, TOC) or synthetic (butylated hydroxytoluene, BHT). The second experiment was a sensory analysis test done by untrained panelists on eggs from hens fed diets with 0 or 10% flax seed and the third experiment was a consumer preference test conducted to gauge end-user response to n-3 fatty acid-enriched eggs. MATERIALS AND METHODS An institutional review board approved all experimental protocols and written consent was obtained from each volunteer by explaining the details of the experiment. Experiment 1 Eggs were obtained from 32-wk-old ISA Brown laying hens fed diets containing 0% flax seed (control), 10% flax seed (flax), 10% flax seed + 100 IU of vitamin E (flax + TOC), or 10% flax seed + 100 mg of BHT (flax + BHT). The laying hen diets were isocaloric and isonitrogenous and provided 2,751 kcal/kg of ME and 16.5% CP as per ISA guidelines for brown layers. The eggs used in the present study originated from a project designed to assess the effect of inclusion of flax seed and antioxidants on egg quality and production performance in brown layers. Information on pullet raising and management, hen diet composition, and results with regard to egg quality, egg fatty acid profile, cholesterol and TOC concentration, and hen production performance were reported earlier (Hayat et al., 2009). After 8 wk of administration of the experimental diets, eggs were collected within 24 h of sensory study and kept under refrigerated storage (4 C). Feeding flax seed had no effect on egg quality aspects (egg weight, yolk weight, shell weight, albumen weight and height, yolk color, and shell thickness) or on egg production (P > 0.05; Hayat et al., 2009). Experiments 2 and 3 The n-3 fatty acid-enriched and control eggs were collected from White Leghorn hens. The hens (n = 300, 35 wk of age) were kept in 2-tiered cages providing 410 cm 2 per hen and were maintained on a 17L:7D Hayat et al. photoperiod. The birds were randomly distributed to 2 dietary treatments of 150 layers each (10 birds per cage and 15 cages per treatment). The layers were fed a corn soybean meal diet with 0 and 10% whole flax seed with 100 IU/kg of vitamin E, respectively. Diets were isocaloric and isonitrogenous (2,800 kcal/kg of ME and 16.5% CP). Feed and water were provided all the times. After 8 wk of feeding the experimental diets, eggs (n = 155/treatment) were collected and kept under refrigerated storage (4 C). Organoleptic Evaluation of Eggs Panelist Selection. Ten (n = 10) panelists (ages 20 to 55 yr) from the Oregon State University Food Science and Technology Department and from the local Corvallis community who were willing to consume eggs and had no allergies to eggs were selected and trained for experiment 1 (Table 1). In experiment 2, 30 (n = 30) untrained panelists were selected from students and staff of the University of Veterinary and Animal Sciences, Lahore, Pakistan, through advertisement on the university campus (Table 2). Food shoppers purchasing eggs at grocery stores in Lahore, Pakistan, having no allergy to eggs and who were willing to participate in the sensory study were selected for experiment 3 as consumers (n = 38; Table 3). The panelists and consumers, all unaware of the dietary treatments, were asked to distinguish flax seed-fed eggs from regular eggs. Institutional approval was obtained and written consent was obtained from each volunteer by explaining the details of the experiment. Panelist Training. Panelists participated in a training session that reviewed testing procedure and egg evaluation techniques. Panelists were introduced to different evaluation techniques (e.g., smelling and tasting eggs). Evaluation of the different testing procedures was discussed. For demonstration purposes, egg cooking time was manipulated to create sensory differences. This was done by bringing the egg water to boil, then turning the heat off, and, with the pot lid left on, holding the eggs in the water for 20, 40, and 60 min, before rinsing in cold tap water to room temperature. Panelists were introduced to difference-from-control methodology and they practiced this method on paper ballots using eggs that were held for 20, 40, and 60 min. Panelists were instructed to cleanse their palate between samples with spring water. Sample Preparation Three eggs from each treatment were added to a 1-quart (~950-mL) stainless steel pot, which contained 32 oz (~900 ml) of ambient tap water and the pot was covered with a lid. The gas range was turned on and kept on the highest heat level (high) until the eggs were brought to a low-rolling boil (at 8.5 min). The heat was turned off and the eggs were kept in the water (lid on)

RESEARCH NOTE 2295 Table 1. Sensory evaluation of eggs from hens fed a control, flax seed, and flax seed with vitamin E (α-tocopherol, TOC) or butylated hydroxytoluene (BHT) by trained panelists, experiment 1 1 Attribute 2 Control Flax Flax + TOC Flax + BHT P-value P-value (panelist treatment) Aroma 1.5 ± 0.14 a 2.5 ± 0.13 b 2.9 ± 0.13 b 2.5 ± 0.13 b <0.001 <0.05 Flavor 1.7 ± 0.18 a 2.9 ± 0.16 b 3.7 ± 0.16 b 3.3 ± 0.16 b <0.001 <0.05 Off-flavor 1.1 ± 0.018 a 2.2 ± 0.16 b 3.0 ± 0.16 b 2.3 ± 0.16 b <0.001 NS 3 Overall difference 1.7 ± 0.17 a 2.9 ± 0.15 b 3.7 ± 0.15 b 3.3 ± 0.15 b <0.001 NS a,b Means within a row with different superscripts are significantly different from one another as indicated by the P-value shown in the table. 1 Means for treatments are based on 9 panelists; n = 9. 2 Based on a 9-point intensity scale where 0 = no difference, 3 = slightly different, 5 = moderately different, 7 = largely different, and 9 = extremely different. 3 NS = not significant (P > 0.05). for 20 min. The water was drained from the pot and the strained eggs were cooled under running tap water, a little cooler than ambient temperature, until the eggs were considered to be at room temperature. The eggs were peeled and then cut into quarters (lengthwise) for delivery to sample plates. One-quarter egg from each treatment was delivered to a 15-cm white paper board plate identified with a 3-digit blind code. Sensory Evaluation Methodology One sample was designated the control and the other samples were 3-digit, blind-coded test samples. One of the blind-coded test samples was also from the control egg. These blind-coded samples were evaluated with respect to how different they were from the control. Each panelist was presented a control sample plus the test samples. Care was taken so that each panelist received a control sample and a blind control sample from the same egg. The sensory attributes tested were a) aroma: odor of the whole egg, b) flavor: the distinctive aroma and taste of the yolk, c) off-flavors: unusual Table 2. Sensory evaluation of hard-boiled eggs by untrained panelists 1,2 Replication Total number of responses 3 Total correct responses 3 smell or taste of the yolk, and d) overall difference: an integrated sensation based on aroma, flavor, aftertaste, and presence of off-flavor (if any). For each of the sensory parameters tested, panelists were asked to rate the difference between each sample and the control using a 9-point intensity scale where 0 = no difference, 3 = slightly different, 5 = moderately different, 7 = largely different, and 9 = extremely different. In addition, a comment opportunity was provided after each attribute, in which panelists could write in comments regarding what they thought about the major differences in the sample provided. Before testing, panelists were informed that some of the test samples might be the same as the control. The resulting mean differencefrom-control estimates were evaluated by comparing them to the mean difference-from-control obtained with the blind controls. Sensory evaluation of hard-boiled eggs by untrained panelists and consumers was based on a triangular test. In this test, each untrained panelist or consumer was given 3 samples of hard-boiled egg, of which 2 samples were similar (from the same egg) and the third was Correct responses percentage Probability Flavor 1 50 11 22.0 NS 4 2 50 15 30.0 NS 3 50 12 24.0 NS Total 150 38 25.3 NS Aroma 1 50 9 18.0 NS 2 50 13 26.0 NS 3 50 14 28.0 NS Total 150 36 24.0 NS 1 Sensory evaluation of hard-boiled eggs by untrained panelists was based on a triangular test. In this test, each untrained panelist or consumer was given 3 samples of hard-boiled egg, of which 2 samples were similar (from the same egg) and the third was different. Each participant was asked to recognize the different egg sample among the 3 given samples. 2 There were 5 testing sessions for 30 untrained panelists in replicates of 10, resulting in a total of 150 observations. 3 Total number of responses = total number of comparisons; total correct responses = number of comparisons in which panelist correctly recognized the different sample. 4 NS = not significant (P > 0.05).

2296 Hayat et al. Table 3. Sensory evaluation of hard-boiled eggs by consumers 1,2,3 Sensory attribute Total number of responses 4 Total correct responses 4 Correct responses percentage Probability Flavor 1 70 17 24.3 NS 5 2 60 14 23.3 NS 3 60 15 25.0 NS Total 190 46 24.2 NS Aroma 1 70 16 22.9 NS 2 60 12 20.0 NS 3 60 15 25.0 NS Total 190 43 22.6 NS 1 Sensory evaluation of hard-boiled eggs by consumers was based on a triangular test. In this test, each untrained panelist or consumer was given 3 samples of hard-boiled egg, of which 2 samples were similar (from the same egg) and the third was different. Each participant was asked to recognize the different egg sample among the 3 given samples. 2 The consumer testing was conducted at 3 places with 14, 12, and 12 participants in 3 replications, respectively. 3 Each consumer was offered 5 triangular sensory tests, generating a total of 190 observations. 4 Total number of responses = total number of comparisons; total correct responses = number of comparisons in which panelist correctly recognized the different sample. 5 NS = not significant (P > 0.05). different. Each participant was asked to recognize the different egg sample based on aroma (odor of the whole egg) and flavor (distinctive aroma and taste of the yolk) among the 3 given samples. Criteria for evaluation were as follows: total number of responses = total number of comparisons; number of correct responses = number of comparisons in which the panelist correctly recognized the different sample. Testing Area, Testing, and Serving Orders For testing, trained panelists were seated in individual testing booths with white lighting. Panelists completed their evaluations using computers (Compusense Five, v5.0 software, version 4.6, Guelph, Ontario, Canada). Each booth was stocked with spring water for cleansing the palate between samples. There were 8 testing sessions; panelists completed 2 testing sessions in a backto-back fashion by attending 4 times across 2 testing days. During each of the 4 testing times, panelists were required to take a ~10-min break between tests (for example, after completing test 1, panelists took a 10- min break before returning to complete test 2). Sensory evaluation by untrained panelists and consumers was conducted in rooms with white lighting on 2 separate days. Fresh clean tap water was provided for cleansing the palate between samples and panelists had 5 min to record their observations. There were 5 testing sessions for 30 untrained panelists in replicates of 10 panelists each. The participants manually recorded their responses on a paper sheet provided for the purpose. The consumer testing was conducted at 3 places in Lahore, with a total of 38 participants. Each location had 14, 12, and 12 participants in first, second, and third setting (replication), respectively. Each consumer was offered 5 triangular sensory tests, generating a total of 190 observations. The participants manually recorded their responses on papers. Statistical Analysis A randomized complete block design was used. For testing sample treatment effects and panelist s performance, the factors included sample treatment or performance, panelist, and panelist treatment (P T) interactions. Sample treatment was a fixed effect and panelist and P T interactions were random effects. An individual ANOVA was conducted for each attribute using PROC GLM (SAS Version 9.1; SAS Institute, 2001). Statistically significant attributes were further analyzed to see where differences exist using least significant means testing at the 95% confidence level (P 0.05). RESULTS AND DISCUSSION Eggs from hens fed flax seed with and without antioxidant supplementation were individually evaluated for sensory aspects. Comparisons were made between each of the 4 treatment groups (control, flax, flax + TOC, and flax + BHT) for aroma, flavor, off-flavor, and overall difference. Results from experiment 1 revealed a significant P T interaction for aroma, flavor, off-flavor, and overall difference (P < 0.001). The P T interaction was due to the inconsistency in scoring by one panelist when compared with the panel mean direction. To determine which panelists were scoring inconsistently and possibly contributing to the significant P T interaction, an individual univariate ANOVA was conducted. It became apparent that one panelist was finding significant differences between the flax and flax + TOC treatments but was rating these mean dif-

RESEARCH NOTE 2297 ferences in the wrong way (in an opposite direction), causing a significant P T interaction. The data for this particular panelist was removed due to the inconsistency observed in coding and the data were reanalyzed (Table 1). Removal of the inconsistent data for one of the panelists led to a lower significance level for aroma and flavor (from P < 0.001 to P < 0.05) and the disappearance of significant P T interaction for offflavor and overall difference. For all sensory parameters tested, panelists found eggs from flax, flax + TOC, and flax + BHT treatments to be significantly different than those from the blind control (P < 0.001; Table 1). Dietary antioxidant supplementation did not alter the aroma, flavor, off-flavor, or overall difference of flax + TOC or flax + BHT to that of flax eggs. The consumer acceptance test was conducted to further investigate the differences between trained panelists and consumer panel judgments on sensory evaluation of eggs from hens fed flax seed. The sensory evaluation of hard-boiled eggs by untrained panelists and consumers revealed that no difference in aroma and flavor could be identified in flax eggs compared with control eggs (Tables 2 and 3). Results of the present study are in agreement with the findings of previous researchers (Van Elswyk et al., 1995; Williams and Damron, 1999; Ayerza and Coates, 2002). Van Elswyk et al. (1992) reported that consumers could not detect a flavor difference in hard-boiled eggs, supporting the conclusion of Marshall et al. (1994) that lipid oxidation did not contribute to detectable off-flavors in flax-fed eggs. These results suggest that only trained panelists were able to find differences in egg organoleptic attributes in eggs from hens fed 10% flax seed. Addition of 100 IU of TOC led to over an 11-fold increase in egg TOC in the current study (Hayat et al., 2009). However, the extra TOC in the egg did not enhance acceptability of eggs. It should be noted that in the current study, eggs collected within 24 h were used for study. Antioxidants such as vitamin E and BHT are added to provide protection for the polyunsaturated fatty acids and thus protect against oxidative rancidity. It is not known if the presence of vitamin E or BHT in feed will have any added protection or improvement in the organoleptics of eggs during short- or long-term storage. However, Leeson et al. (1998) reported inability of vitamin E in altering the sensory aspects and overall acceptability of 10 or 20% flax eggs stored over 14 d. We are unaware of any other comparable data with organoleptic evaluation of eggs from hens fed 2 different types of antioxidants. It should be pointed out that the studies were conducted with 2 different hen strains (ISA Brown and White Leghorn) in 2 different countries (United States and Pakistan) with feed from different sources. However, every effort was made to make other factors such as egg collection, storage, and cooking procedures similar in all 3 experiments conducted. Consumer acceptability of eggs laid by the hens fed flax seed showed that hen diet supplementation with flax seed may be a potential alternative for the production of more nutritious eggs for an increasing ready-to-eat and healthconscious food market. In light of results obtained from the present study, it can be concluded that flax seed when incorporated at 10% in the layer diet can produce eggs that are acceptable to the health- and taste-conscious consumers. However, trained panelists are able to detect differences in flavor, aroma, off-flavor, and overall difference in n-3 fatty acid-enriched eggs from flax seed-fed hens. 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