Consumer acceptance of UV-C treated liquid egg products and preparations with UV-C treated eggs

Innovative Food Science and Emerging Technologies 14 (2012) 107–114

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Consumer acceptance of UV-C treated liquid egg products and preparations with UV-C treated eggs Poliana Mendes de Souza a, b, Avelina Fernández a,⁎ a b

Instituto de Agroquímica y Tecnología de Alimentos, CSIC, Avda. Agustín Escardino, 7, 46980 Paterna, Spain Pontifícia Universidade Católica do Paraná, Rua Imaculada Conceição, 1155, 80215–901 Curitiba, Brazil

a r t i c l e

i n f o

Article history: Received 12 November 2011 Accepted 16 December 2011 Editor Proof Receive Date 13 January 2012 Keywords: Minimal processing Non-thermal processing Ultraviolet Egg Consumer acceptance Organoleptic Sensory evaluation

a b s t r a c t The impact of short wave ultraviolet (UV-C) treatments on the organoleptic attributes of liquid egg products (raw or cooked: egg white, egg yolk, whole egg) and products containing UV-C treated liquid egg products as ingredient (mayonnaise, pudding, angel cake) is evaluated. Consumers were asked to distinguish between samples in triangle tests, and to express the degree of liking in acceptance tests. UV-C (5 to 30 min) or heat (following USDA ARS 74–48, 1969) resulted in comparable microbial losses for each product. UV-C treated liquid egg products could not be differentiated from the control below 25 min treatments. Processed egg fractions, cooked, or in egg preparations, could not be differentiated from the controls, either if heated or treated under UV-C during 30 min. Likely, overall scores for the sensory parameters evaluated indicated an acceptability of UV-C treated egg fractions or their preparations not significantly different from that of untreated and they were perceived as comparable to, or, in some cases, better than the thermally pasteurized eggs. No off-flavours due to UV-C treatments were reported. This study confirms no adverse effects on consumer acceptance of egg products processed by UV-C, with overall appearance or taste similar to the controls. Those findings are valuable to further consider UV-C treatment of eggs as a feasible alternative to heat. © 2012 Elsevier Ltd. All rights reserved.

1. Introduction Eggs are a highly nutritive complete food, with an enormous relevance as a multifunctional food ingredient due to their technological properties. Liquid eggs, in addition to their nutritional value, contribute with some unique functional properties such as foaming, whipping, gelling, or emulsifying (Davis & Reeves, 2002), and are extensively used in the industrial production of bakery goods, confectionaries and ice cream (Stadelman, 1999). These properties of eggs can be easily impaired by heat, thus liquid egg pasteurization is conducted on a critical temperature-time regime where the coagulation of egg proteins is prevented (Mukhopadhyay Tomasula & Luchansky, 2009). The U.S. Department of Agriculture (USDA, 1969) demands that liquid egg whites are heated at 56.6 °C for not less than 3.5 min; same time and higher temperatures are required for whole eggs (60 °C), and egg yolks (61.1 °C). Contrary to the limitations of thermal treatments for liquid egg products, UV-C radiation appears as an alternative and cost-effective non-thermal process in order to achieve microbiologically safe and shelf-stable products (Bintsis, Litopoulou-Tzanetaki, & Robinson, 2000; Geveke, 2008; Ngati, Smith, & Cayouette, 2006; Schmidt & Kauling, 2007). The use of ultraviolet light at germicidal wavelengths has been approved for food surfaces and clear fruit juices (US-FDA,

⁎ Corresponding author. Tel.: + 34 963900022; fax: + 34 963636301. E-mail address: [email protected] (A. Fernández). 1466-8564/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.ifset.2011.12.005

2002). The limitations in the germicide capacity of UV-C depend on intrinsic factors such as the chemical composition and the absorption coefficient of solids or large suspended particles, and of external factors such as the light intensity, or the temperature (Koutchma, Kellerb, Chirtelc, & Paris, 2004; Unluturk, Atilgan, Baysal, & Tari, 2008). Therefore to identify target food matrices it is first relevant to analyze specifically the effects of UV on microbial inactivation and food quality attributes. For this, experiments in batch or under laminar flows are providing reliable information on the microbial inactivation of microorganisms and the quality deterioration in liquid and solid foods (Bhat, Ameran, Voon, Karim, & Tze, 2011; Bolton & Linden, 2003; Noci et al., 2008). Particularly in eggs, it is known that sensory and functional properties are sensitive to irradiation (Farkas, 1998). However, some works, such as Serrano, Murano, Shenoy, and Olson (1997), showed that relatively low doses, up to 1.5 kGy, would be sufficient to eliminate Salmonella from whole shell eggs and liquid whole eggs without significant adverse effects on the egg quality. Likely, de Souza and Fernandez (2011) found excellent perspectives for Salmonella inactivation in liquid egg products under UV-C radiation and concluded that low UV-C doses do not affect remarkably the investigated quality attributes (pH, colour, viscosity, lipid oxidation), being the higher doses milder than conventional pasteurizations for those parameters. The instrumental analysis of physicochemical parameters shows therefore excellent perspectives for the UV-C treatment of liquid egg products, but those results do not guarantee consumer acceptance

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of the UV-C treated food. Consequently, this study focuses on a sensory evaluation of the impact of short wave ultraviolet treatments on key organoleptic attributes of liquid egg products and products containing UV-C treated liquid eggs as ingredient. For this analysis, consumers were asked to distinguish between samples in triangle tests, and to score the degree of liking of such products in acceptance tests. 2. Material and methods 2.1. Materials Fresh eggs were purchased from Fazenda Rio Grande (Curitiba, Brazil). They were of yellow shell, and weighted between 55 and 61 g. After reception, eggs were inspected for shell integrity and damaged eggs were discarded. Just before experiments were carried out, the egg content (separately, egg whites and egg yolks) was removed under aseptic conditions, and collected in sterile containers. The pH of the samples was controlled before proceeding with the experiments and eggs were considered to be fresh when pH were around 7.2 ± 0.2 for egg white, and 6.2 ± 0.2 for the egg yolk. The chalaza was removed and the separated egg fractions were homogenized for one min using a vortex (QL901, Biomixer, Brazil), at 3000 rpm. To prepare the whole egg samples, 13.3 mL of egg yolk were mixed with 26.7 mL of egg white. Ingredients required to prepare egg containing food products (angel cake, pudding and mayonnaise) were acquired in a local supermarket. Components requiring low temperatures were preserved in a refrigerator until experiments were carried out. 2.2. UV-C irradiation of egg samples Following Bhat et al. (2011), UV radiation of samples at germicide wavelengths was conducted in batch in a UV bench scale chamber designed by UV-Consulting Peschl® España (Burjassot, Valencia, Spain) with dimensions 55 × 35 × 55 cm. The chamber is provided with one low pressure mercury lamp with 7.3 W output and 436 mm length (Heraeus Noblelight GmbH, Hanau, Germany), with maximum peak radiation at 253.7 nm. Samples (12 mL volume; 0.2 cm height) placed in sterile polystyrene 60.3 cm 2 Petri dishes, were treated up to 30 min in 5 min intervals. Samples were situated at 10 cm from the lamp, and were continuously stirred during irradiation with magnetic stirrers at 400 rpm (AGM-5AQ, Arsec, Brazil). Under similar conditions, UV doses up to 4.2 Jcm − 2 after 30 min were estimated by actinometry with the same lamp (Corrales, de Souza, Stahl, & Fernandez, in press). Samples were irradiated at room temperature (20 °C) UV-samples were prepared in batches and stored under refrigeration until the necessary amount of product was treated; sensory evaluation of fresh liquid egg products was carried out immediately thereafter. Untreated and pasteurized samples were kept under the same conditions. For the cooked eggs and egg containing products, the egg preparation was the same as for the fresh product, and the cooking or product preparing was done immediately after the necessary amount of sample was collected. 2.3. Heat treatment Intending to compare the UV treatment with treatments equivalent to conventional pasteurizations, one mL ampoules of whole egg, egg yolk or egg white were treated using a thermostatic bath (TBA23, SP Labor, Brazil) set to 56.6 °C, 60 °C and 61.1 °C for egg white, whole egg and egg yolk, respectively. The conditions for pasteurisation were chosen in conformity with the requirements of the USDA (USDA ARS 74–48, 1969). The holding time used for the three

fractions was 3.5 min when the coldest point of the sample attained the pasteurization temperature. 2.4. Preparation of cooked eggs Untreated, pasteurized or UV treated egg whites, whole eggs and egg yolks samples were homogenised in an electric mixer (Eletronic filter, Britânia, Brazil) during one minute and disposed in aluminium capsules (10 cm length, 4 cm diameter) until they were completely filled. The capsules were boiled in a water bath during 10 min and then allowed to cool down to room temperature. The cooked eggs were extracted from the capsules and cut into one cm thick slices. 2.5. Preparation of mayonnaise Mayonnaise was prepared with the treated (UV-C or heat pasteurized) or untreated whole eggs using the following formula: egg (30%), sunflower oil (67%), salt (2%) and lemon juice (1%). The mixing of ingredients was performed using an electric mixer (Eletronic Filter, Britânia, Brazil). Oil was added slowly to the egg under continuous mixing to form the emulsion; after oil has been added, mixing continued for 5 min. This was followed by the addition of the lemon juice and salt, and mixing for additional 5 min. The mayonnaise was kept refrigerated at 10 °C until sensory analysis was carried out. 2.6. Preparation of puddings Puddings containing untreated, pasteurized or UV treated whole eggs were prepared using the following formula: egg (20%), condensed milk (40%) and whole milk (40%). The mixing of ingredients was performed using an electric mixer (Eletronic filter, Britânia, Brazil) during 10 min. The mixture was transferred to a non-stick aluminium pan with central hole and baked in a boiling water bath during 1 h. The pudding was put in a refrigerator and was allowed to cool down in the mould until 10 °C were achieved. 2.7. Preparation of angel cakes Angel food cake was prepared with the treated (UV or heat pasteurized) or untreated egg whites using the following formula: egg white (57.7%), sugar (24.2%), flour (13.4%), corn starch (3.4%), tartar cream (0.9%) and salt (0.4%). A planetary mixer (SX80, Arno, Brazil) was used to prepare the cakes. First, egg whites were mixed with the salt and tartar cream for 10 min while the other ingredients were hand mixed. The handmade mixture was slowly added to the mixer. The preparation was instrumentally mixed for 10 min prior to baking. The cake flour was sifted, combined, and mixed at low speed with the remaining sugar for at least 20 s. Baking took place at 175 °C for 45 min. Then cakes were cooled in an inverted position at room temperature. 2.8. Microbial evaluation of UV-C treated fresh liquid products Total aerobic counts were evaluated on Plate Count Agar (PCA, Scharlau, Germany) after decimal dilutions in 0.1% peptone water using a pour plate technique. Total mesophilic microorganisms (MEC) were incubated at 30 °C for 48 h and enumerated. Total psychrotrophic microorganisms (PSC) were incubated at 22 °C for 120 h and enumerated (Gonzales et al., 2009). 2.9. Evaluation of sensory differences Triangle tests were carried out in order to evaluate the differences between untreated, UV or pasteurized liquid egg products and products containing untreated, UV or pasteurized liquid egg products. For these experiments three samples were served to each member of the panel,

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two of them equal, and one different, and the panel was asked to identify which of the samples was different (ASTM, 1968; Dutcosky, 1996). The panel was composed by 50 not trained members, volunteers, from both sexes, aging between 18 and 50 years old, who have reported the habit of consuming eggs. The test runs were grouped as follows: UV-C treated-pasteurized; without treatment-UV-C treated; and without treatment-pasteurized. Tests between ultraviolet treated and pasteurized samples proceeded with the highest UV doses. Tests to identify differences between the ultraviolet treated and the non-treated samples started with the lowest UV doses. The experiments were carried out in 3 steps: first, the evaluation of the natural liquid egg products without preparation; second, the evaluation of the cooked products; and third, the evaluation of egg preparations. On the first step, three 30 mL samples were served in white cups randomly numbered, and panelists were asked to identify the different sample from the group without any indication about which sensorial parameter should be analyzed. These experiments were repeated asking the jury to focus on the colour, and later on the aroma. The products analyzed here were liquid egg fractions natural, pasteurized or UV-C treated. On the second step, three samples of 3 slices of 1 cm (height) × 4 cm (diameter) of the cooked egg products were served to the panel in white plates randomly numbered, and panelists were asked to identify the different sample from the group. The products analyzed here were cooked egg fractions natural, pasteurized or UV-C treated. On the third step, triangular tests were used in order to evaluate if the consumers were able to identify differences between the products based on UV treated eggs from the products using non treated eggs, or pasteurized eggs. Pudding and mayonnaise were prepared with whole eggs and angel cakes were prepared with egg whites treated during 30 min (highest UV dose used in this study). 25 mL of mayonnaise were tempered up to 15 °C and served to the panel in white plastic cups randomly numbered. Pieces of approximately 5 × 5 × 1 cm of pudding were tempered up to 15 °C and served on plastic white dishes randomly numbered. And pieces of the angel cake of approximately 6 × 6 × 4 cm were served to the panel also in white plastic dishes randomly numbered at ambient temperature. 2.10. Consumer affective test To verify the acceptability of the products prepared with UV treated eggs compared to natural and pasteurized eggs a 9-point hedonic scale was used, as described by Dutcosky (1996). Evaluations were performed by 50 untrained sensory panelists between 18 and 50 years old. Panelists were volunteers prescreened for potential food allergies and on the basis of being egg and egg products consumers. Panelists were provided with an instruction/score sheet with specific instructions for evaluating the samples. Samples were offered to panelists on odourless plastic plates or cups coded by three-digit random numbers at room temperature. The order of serving was determined by random permutation. Questionnaires were provided with samples. Panelists were instructed to use unsalted crackers and mineral water to cleanse their palate before tasting the samples and any time during the test, as needed. The panelists evaluated the food preparations on a 9-point hedonic scale to determine degree of liking (9 = like extremely, 5 = neither like nor dislike, 1 = dislike extremely). Angel cake samples were rated for colour, flavour, aroma, sponginess, humidity, after flavour, appearance and overall acceptability on the same scale. Mayonnaise samples were rated for colour, flavour, aroma, texture, creaminess, firmness, after flavour, appearance and overall acceptability. And pudding samples were rated for colour, flavour, aroma, texture, after flavour, appearance and overall acceptability. The panelists were also asked to evaluate the presence of off flavours on each preparation using a 9-point hedonic scale where 9 = presence of good off flavour, 5 = no presence of off flavour, 1 = presence of bad off flavour.

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The panel received the differently treated samples (cooked using liquid egg samples treated during 30 min with ultraviolet, or heat treated, or untreated) of each product type, randomly numbered. Mayonnaise samples were served at 15 °C; pieces of approximately 5×5×1 cm of pudding were served at 15 °C; and pieces of angel cake of approximately 6×6×4 cm were served at ambient temperature. The overall quality Q was calculated using the following equation (García, Butz, Bognàr, & Tauscher, 2001): Q¼

ð3xC Þ þ ð5xAÞ þ ð8xT Þ þ ð4xHÞ 20

where: C = colour; A = aroma; T = taste; H = harmony, or overall acceptability. 2.11. Colour measurement Colour changes were quantified through the CIELAB colour space coordinates (L*, a*, and b*) obtained by a spectrocolorimeter (Hunter Labscan II, Minolta, Tokyo, Japan), equipped with D65 as the light source, and using an observation angle of 10°. The spectrocolorimeter was calibrated with standard black and white tiles, and is equipped with a Colour Data Software CM-S100w Spectra magic NX (Konica Minolta, Tokyo, Japan). Six liquid egg fractions samples were tested for each treatment. 2.12. Apparent viscosity Apparent viscosity was measured at 25 °C in a concentric-cylinder viscometer (Fisher Bioblock Scientific, Illkirch, Belgium) at 30 rpm, data were gathered in OS550 software. Twenty readings were recorded from each of triplicate liquid egg samples prepared per treatment (Wardy et al., 2011). 2.13. Statistical analysis The triangle test results were evaluated by comparison to tables presented by O'Mahoni (1986). With n = 50, significant differences at a 95% confidence level are established when 23 panelists correctly identify the different sample; for a confidence level of 99%, the number of correct answers should be 26; and for a confidence level of 99.9%, at least 28 correct answers must be attained. Other results were statistically evaluated by one-way analysis of variance (ANOVA) with XLSTAT-Pro (Win) 7.5.3 (Addinsoft, NY), with a 95% confidence level. Comparisons between treatments were evaluated with the Tukey test. 3. Results and discussion 3.1. Microbial analysis The equivalence of the treatments was evaluated as a function of the microbial inactivation achieved. Data on the effects of 30 min UV-C irradiation and heat treatments on the microbial loads of liquid egg products are provided in Table 1, which are also useful to compare the treatment intensity (and the expected sensory attributes) among UV-C equipments. Total counts of mesophilic aerobic bacteria and psychrotrophic microorganisms in liquid whole eggs are comparable to the ones presented by Gonzales et al. (2009) Parameters used here provided effective reductions in egg white by both sanitization methods, and counts were below the detection limit (10 cfu mL − 1) after heat and UV-C treatments. Regarding egg yolk and whole egg, inactivation achieved was comparable in heat sanitized or UV-C treated samples. However, none of the treatments have been able to reduce the viable cells below the detection limits. The optical density of the products is an important factor to be considered with regard to UV-C treatments (Koutchma, 2009); high optical densities do not

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Table 1 Effects of UV-C or heat on the microbial loads of liquid egg products. Type of product

Treatment

Mesophilic counts (log CFU mL− 1)

Psychotrophic counts (log CFU mL− 1)

Egg white

Natural UV 30 min Pasteurized Natural UV 30 min Pasteurized Natural UV 30 min Pasteurized

4.60 ± 0.32 b1.00 b1.00 4.88 ± 0.22a 1.70 ± 0.16b 1.78 ± 0.18b 5.02 ± 0.29a 3.04 ± 0.15b 2.78 ± 0.16c

4.71 ± 0.18 b1.00 b1.00 4.93 ± 0.14a 2.58 ± 0.20b 2.10 ± 0.31b 5.07 ± 0.16a 2.98 ± 0.17b 2.12 ± 0.24c

Whole egg

Egg yolk

Values with different superscripts within a column for each product are significantly different (P b 0.05), as determined by the Tukey's test at the 95% confidence level.

enable the transmittance of UV light and result in lower microbiological reductions, as it has been shown for UV-C treated liquid egg products (Unluturk et al., 2008). Optical density for egg fractions is as follows: egg whiteb whole eggb egg yolk (Souza & Fernandez, 2011) and is highly related to the antimicrobial effectiveness of the UV-C treatment. 3.2. Sensory evaluation: difference Cross results for the highest UV-C dose (30 min), heat treatments and controls are reported on Table 2. When fresh products were evaluated, the lowest differences were found in egg whites. The sensory panel has not found significant differences up to the 99.9% confidence level when untreated and UV-C treated egg whites were compared in the entire UV time range studied (from 5 to 30 min); a similar result was found when heat treated and UV-C treated samples were compared. The panel was however able to differentiate the untreated from the heat treated egg white samples at the 95% confidence level, pointing out only small differences in the general appearance, which are more evident if individually colour or aroma are considered. Heat treated samples were graded as having a cooked flavour by some panelists. More remarkable are the effects on egg yolk and whole egg. The panel could identify differences between the untreated and UV-C treated samples after 25 min treatment (from 5 to 25 min, non significant differences at the 99.9% confidence level). Whole egg samples were significantly different at the 95% confidence level after 30 min, while yolk samples showed stronger differences, being data significantly different up to the 99.9% confidence level. Those results indicate a remarkable effect of UV-C radiation on sensory parameters for the egg fractions

containing fat, in accordance with previously published data on the effects of UV-C on the evolution of the TBARS index in UV-C treated whole egg and egg yolk samples (de Souza & Fernandez, 2011). Remarkably, heat treated whole egg and egg yolk samples were significantly different from the control and the UV-C treated samples up to 25 min treatment, confirming the stronger similarities between the UV-C treated samples and the control. Such effects are also found when colour and aroma are evaluated individually, and only the samples treated during 30 min are not significantly different from the heat treated ones for both parameters at the 99.9% confidence level. Egg cooking or baking are processes where egg protein denaturation takes place, and therefore conditioned by pH (Davis & Willians, 1998), protein quality (degree of oxidation), and egg functional properties (foaming and emulsifying properties). Sensory results point out that cooking or baking of UV-C treated or heat treated egg fractions minimized the differences in all investigated parameters. Remarkably, the panel has not found significant differences on the quality of the cooked products, and the general appearance of heat or UV-C treated egg fractions, and more specifically colour and aroma, were not found different to the control. Only a significant effect was observed for the general appearance of the heat treated egg yolk compared to the control. In a similar way, the baked products (pudding and angel cake) have not shown significant differences up to the 99.9% confidence level regarding the general appearance, the colour or the aroma. Consequently, the similarities found between the processed egg fractions point out for a minimal effect of UV-C treatments on the egg foaming and emulsifying properties. UV light at germicide wavelengths is known to generate small changes in physicochemical properties and should not alter, for example, the pH of food (Souza & Fernandez, 2011; Torkamani & Niakousari, 2011), but could be oxidizing (Muruganandham & Swaminathan, 2004; Wang, Hsieh, & Hong, 2000). Therefore more specific tests about hedonic markers might provide a further insight into potential quality changes in preparations containing UV-C treated egg products. Regarding mayonnaise, significant differences (95% confidence level) were reported between the natural and the 30 min UV-C treated samples. Panelists indicated that the UV-C treated sample was firmer than the natural, even if they could not find differences in the colour or the aroma. 3.3. Consumer acceptance test Colour and aroma are probably the most relevant quality attributes for fresh eggs and liquid egg products because they are simple indicators of

Table 2 Correct answers in a triangular test by treatment comparison at the highest UV dose (30 min). Results cross the column and row treatment parameters. ′, ″ and ‴, indicate significantly different at the 5, 1 and 0.1% significance level, respectively. Sensory parameters

General impression

Colour

Aroma

Type of product

Treatment comparison

Natural

Pasteurized

Natural

Pasteurized

Natural

Pasteurized

Whole egg

UV 30 min Natural UV 30 min Natural UV 30 min Natural UV 30 min Natural UV 30 min Natural UV 30 min Natural UV 30 min Natural UV 30 min Natural UV 30 min Natural

24′

16 41‴ 17 23′ 21 39‴ 16 22 14 17 19 23′ 16 19 16 18 16 17

27″

21 44‴ 14 26″ 20 39‴ 18 14 16 21 18 20 17 22 15 20 13 20

23′

18 42‴ 16 29‴ 22 40‴ 18 14 15 16 15 20 18 20 16 19 14 20

Egg white Egg yolk Cooked whole egg Cooked egg white Cooked egg yolk Mayonesse Puding Angel cake

16 32″ 13 8 18 24′ 16 13

18 33‴ 12 15 22 17 17 18

20 34‴ 12 17 17 22 19 15

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microbiological spoilage. A green colour or a sulphur smell are related to the characteristic appearance of rotten eggs, and indicate the end of shelflife. Changes in egg rheological behaviour are also typically associated to protein denaturation, and may occur during pasteurization (Douglas, Greenberg, Farrell, & Edmondson, 1981) and egg irradiation with ionising sources (Min et al., 2005). Consequently, in the present study, the consumer acceptance of egg fractions treated with different methods was evaluated by asking the degree of liking on 9-point hedonic scales for 5 different parameters: colour, aroma, viscosity, appearance and general acceptance. When fresh egg white, egg yolk and whole egg were evaluated, the acceptance scores for all treatments were fairly similar in all the investigated categories (Fig. 1), giving slightly lower scores only for heat treated egg whites. Discrimination tests also demonstrated previously that consumers were able to differentiate only scarce effects of processing on the egg fractions, confirming that heat treated samples were the most different to the control. Consumers seem to have a similar degree of acceptability for all the products, which obtained rather low scores in the “like slightly” range of the scale because fresh egg products are relatively flat in odour and flavour, and they are not consumed raw. But the panelists seem not to have distinguished any particular discolorations or

(a)

off-flavours after 30 min UV-C or regular heat treatments, being the colour scores the highest in this group. The most pronounced difference, which still was not significant (P>0.05), was observed on the egg white viscosity after heating, where heat could have promoted a certain degree of protein coagulation. Protein coagulation could be then responsible for an apparently different viscosity, and the lower scores generally found for the heat treated egg whites. For cooked egg products, colour, aroma, appearance, flavour, after taste and general acceptance were analysed (Fig. 2). The reported scores show no discrepancy between treated products and the controls, and results again point out for a minimization in the differences after cooking. The parameters analyzed confirm that the taste of cooked egg fractions sanitized by heat or UV-C is as acceptable as that from natural eggs. Flavour and colour received the highest scores, while in general, the aroma was scored rather low (“dislike moderately” to “dislike slightly”) for all the products. These low aroma scores are likely due to the fact that the cooked egg products were served without added ingredients (oil, salt, pepper, etc.), contrary to the usual way of consumption, not individually but as part of a meal. The off-flavour average score observed in all samples

(a) 9

Natural

Pasteurized

9

5

5

4

4

3

3

2

2

1

1 Colour

Aroma

Viscosity

Natural

Colour

Aroma Appearance Flavour

After taste General

General

Appearance

(b) 9

Pasteurized

9

Natural

Pasteurized

UV 30min

8

UV 30min

8

7

7

6

6

5

5

4

4

3

3

2

2

1 Colour

1 Colour

Aroma

Viscosity

Appearance

Natural

Pasteurized

Aroma Appearance Flavour

After taste General

General

(c)

9

Natural

Pasteurized

UV 30min

8

UV 30min

8

7

7

6

6

5

5

4

4

3

3

2

2 1

UV 30min

6

6

9

Pasteurized

7

7

(c)

Natural

8

UV 30min

8

(b)

111

1 Colour Colour

Aroma

Viscosity

Appearance

Aroma Appearance Flavour

After taste General

General

Fig. 1. Hedonic scale grades attained by (a) liquid egg white, (b) liquid whole egg, and (c) liquid egg yolk without treatment, heat treated, or UV-C treated during 30 min.

Fig. 2. Hedonic scale grades attained by (a) cooked egg white, (b) cooked whole egg, and (c) cooked egg yolk prepared with eggs without treatment, heat treated, or UV-C treated during 30 min.

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radiation on the volatile profile is matrix dependent. In the work of Manzoco et al. (2011), a sensory panel discarded the presence of off-flavours attributed to UV-C treatment during the storage of apple slices, and the light seem not to have induced differences in the physiological ripening of the fruit. Similarly to our results, in apple cider, triangle tests revealed no significant differences between the control and the treated samples (heat, UV-C, PEF) at day 0 (Valappil, Fan, Zhang, & Rouseff, 2009). However, significant differences (P ≤ 0.05) were observed after 4 weeks storage, being the control preferred over the UV-C treated sample probably due to the loss in hexanal and the increase in 1-hexanol, together with some sensory notes associated to microbial growth. Therefore, the variety of results available point out for the necessity of individualized analysis for each product, and the studies ought to be extended up to the end of product shelf-life.

Table 3 Consumer acceptance ratings specifically for off-flavour on cooked egg white, cooked whole egg, cooked egg yolk, mayonnaise, pudding and angel cake; and overall quality calculated from the aroma, flavour, colour and harmony (general acceptance). Type of product Cooked egg white

Cooked whole egg

Cooked egg yolk

Mayonnaise

Pudding

Angel cake

Treatment Natural UV 30 min Pasteurized Natural UV 30 min Pasteurized Natural UV 30 min Pasteurized Natural UV 30 min Pasteurized Natural UV 30 min Pasteurized Natural UV 30 min Pasteurized

Off-flavour a

5.1 ± 2.1 5.3 ± 2.3a 5.0 ± 1.2a 4.8 ± 1.0a 5.0 ± 1.1a 4.4 ± 1.6a 5.2 ± 1.3a 5.0 ± 1.4a 4.9 ± 1.6a 5.0 ± 0.7a 5.1 ± 0.8a 4.2 ± 1.1a 4.9 ± 1.5a 5.4 ± 1.3a 5.2 ± 2.1a 5.5 ± 1.2a 5.2 ± 1.6a 5.0 ± 1.4a

Overall quality 5.7 ± 1.2a 5.8 ± 1.6a 5.6 ± 1.7a 6.8 ± 1.7a 6.6 ± 1.4a 6.4 ± 1.6a 5.7 ± 1.5a 5.9 ± 1.4a 5.7 ± 1.5a 6.8 ± 1.8a 7.2 ± 1.6a 6.5 ± 2.0a 7.2 ± 1.6a 7.7 ± 1.3a 7.4 ± 1.4a 6.7 ± 1.6a 6.8 ± 1.8a 6.4 ± 1.7a

3.4. Physicochemical properties of fresh liquid egg fractions The most obvious changes during the treatment of liquid egg products are typically related to colour. Results concerning heat and UV-C treatments are recorded on Table 2. After the treatments all the fractions increased moderately the values for red (+a*) and yellow (+ b*), resulting in more orange products with an increased difference at the higher doses (longer periods of UV-C exposure). Also, the L* value decreased with the exposure time, and results for heat treated samples are comparatively darker than the others. In similar products, de Souza and Fernandez (2011) found a comparable tendency for the CIELAB colour coordinates. Consequently, results obtained instrumentally would justify the triangle tests results for fresh products, being the Maillard reaction likely responsible for the observed differences. At low shear rates and 25 °C, no time-dependency is expected for egg viscosity (Atilgan & Unluturk, 2008). Therefore the apparent viscosity is here represented as the average of 20 measurements at a shear rate of 30 rpm. As a consequence of the UV-C or heat treatments, all the liquid egg products showed significant differences to the control, with a tendency to decrease at the highest UV-C doses. Confirming data of Jaekel and Ternes (2009), heat treated egg whites and whole eggs were more different to the control than the UV-C treated ones; while heat treated egg yolk, was more similar to the lowest doses of UV-C. de Souza and Fernandez also observed that UV-C treated egg white and whole egg fractions provided results closer to the native than heat treatments. Therefore, and in contrast with the strong effects of ionizing irradiation (Bachir & Zeinou, 2006; Min et al., 2005) of egg whites on the product viscosity, the apparent viscosity of UV-C treated liquid egg products seem not to be negatively influenced by the treatment. The consumer tests confirmed those results, with scores similar to the controls for fresh products. Only the egg white scores reflected a certain influence of the heat treatment, as commented above.

Values with different superscripts within a column for each product are significantly different (P b 0.05), as determined by the Tukey's test at the 95% confidence level.

(Table 3) indicates that treatments have not induced the formation of any particular off-flavour. Sensory defects in UV-C treated food products are mainly attributed to the oxidation of sulphur containing aminoacids, but off-flavours typically fade during time. Here, samples were collected during a few hours until sensory analysis took place. The lag time could have contributed to the otherwise remarkably low defects in egg products due to light treatments (Table 4). Results for mayonnaise, pudding and angel cake are represented on Fig. 3. Here, colour, flavour, aroma, texture, after flavour, and especially for mayonnaise, creaminess and firmness, were evaluated. Acceptance scores were comparable in all attribute categories (P≥ 0.05), and in overall liking, with responses being in the “like moderately” to the “like very much” range of the scale. Remarkably, the general acceptance attained for the preparations is considerably higher than the scores attained for plain cooked liquid egg fractions. Regarding mayonnaise, consumers showed a certain degree of preference for the samples prepared using UV-C treated whole egg, also reflected on the overall quality scores (Table 3), being the scores obtained by texture and firmness considerably higher than in controls and in heat treated samples. Egg functional properties are highly related to the texture, creaminess, and firmness achieved in preparations. Consequently, results would indirectly confirm that the foaming and emulsifying properties of UV-C treated samples are not negatively affected by the treatment (Table 5). Only a few studies deal with the organoleptic attributes of UV-C treated food, and to our knowledge, no consumer acceptance studies have been carried out on UV-treated eggs. The impact of UV-C

Table 4 CIELAB a*, b* and L* colour coordinates in egg fractions submitted to pasteurization or UV-C. Each sample was measured in 5 different positions; results are the mean of three independent replications. Egg white

Whole egg

Egg yolk

Treatment

a*

b*

L*

a*

b*

L*

a*

b*

L*

Untreated UV 5 min UV 10 min UV 15 min UV 20 min UV 25 min UV 30 min Pasteurized

0.77 ± 0.04a 0.78 ± 0.05a 0.82 ± 0.07a 0.84 ± 0.05a 0.85 ± 0.06a 0.87 ± 0.04a 0.90 ± 0.05a 1.22 ± 0.06b

32.95 ± 1.65a 32.95 ± 1.64a 32.98 ± 1.72a 33.01 ± 1.55a 33.06 ± 1.44a 33.08 ± 1.20a 33.14 ± 1.05a 34.00 ± 1.70a

42.42 ± 2.12a 42.35 ± 2.20a 41.81 ± 2.09a 41.12 ± 2.06a 39.15 ± 2.55ab 36.02 ± 2.84bc 33.13 ± 1.66cd 30.23 ± 1.51d

19.71 ± 0.99a 19.77 ± 1.15a 19.96 ± 1.06a 20.16 ± 1.22a 20.36 ± 1.02a 20.77 ± 1.15a 21.43 ± 1.07a 23.25 ± 1.34a

47.13 ± 2.36 47.20 ± 2.36a 47.47 ± 2.55a 47.71 ± 3.51a 48.10 ± 1.98a 48.65 ± 2.56a 50.15 ± 2.78ab 52.24 ± 3.15b

63.36 ± 3.17a 62.97 ± 3.15ab 62.28 ± 3.11ab 61.40 ± 3.55abc 60.80 ± 2.55abc 59.36 ± 2.94abc 56.98 ± 2.73cd 53.13 ± 2.56d

27.41 ± 1.37a 27.43 ± 1.37a 27.67 ± 1.38a 28.12 ± 1.41a 28.44 ± 1.33ab 29.51 ± 1.55ab 30.72 ± 1.69b 30.62 ± 0.95b

69.78 ± 3.49a 72.49 ± 3.62a 76.55 ± 3.83a 78.74 ± 2.95a 78.98 ± 4.15a 79.71 ± 3.86a 80.18 ± 4.14a 81.53 ± 4.55a

59.33 ± 2.97a 59.05 ± 2.95a 58.26 ± 2.03a 57.59 ± 2.58a 56.79 ± 2.94ab 55.03 ± 2.55abc 51.93 ± 2.60bc 50.83 ± 2.54c

Values with different superscripts within a column are significantly different (P b 0.05), as determined by the Tukey's test at the 95% confidence level.

P.M. de Souza, A. Fernández / Innovative Food Science and Emerging Technologies 14 (2012) 107–114

(a)

pudding or angel cake. The overall visual and sensory acceptability of UV-C treated liquid egg products were not significantly different from that of untreated or heat treated products. Products containing UVtreated egg samples were perceived as comparable to or, in some cases, better than the heat treated. No off-flavours due to UV-C treatments were reported. In egg preparations, consumers also found no differences that could be related to UV-C induced changes in egg functional properties (foaming or emulsifying). Results confirm UV-C as a technology with high potential to minimize the risks associated to microbial contamination in liquid egg products, with very low effects in the physicochemical parameters and excellent consumer acceptability for the treated products.

9 8 7 6 5 4 3 2 Natural

1

(b)

Colour

Pasteurized

Flavour

Aroma

113

UV 30min

Texture Creamy Firmness General

After Appearance flavour

9

Acknowledgements

8

Authors are indebted to the Pontifícia Universidade Católica do Paraná for the installations and the technical assistance during the experiments. Authors acknowledge financial support through the Consolider Project Fun-C-Food CSD2007-00063 of MICINN. de Souza, P. M. thanks the Generalitat Valenciana for Grant number BFPI/2008/ 230.

7 6 5 4 3

References

2 Natural

1 Colour

(c)

Pasteurized

Flavour

Aroma

UV 30min

Texture Creamy Firmness General

After Appearance flavour

9 8 7 6 5 4 3 2 Natural

1

Colour

Pasteurized

Flavour

Aroma

UV 30min

Texture Creamy Firmness General

After Appearance flavour

Fig. 3. Hedonic scale grades attained by (a) mayonnaise, or (b) pudding, prepared with not treated, pasteurized or UV treated whole eggs, and (c) angel cake, prepared with untreated, heat, or UV-C treated egg whites.

4. Concluding remarks Consumers could not differentiate the UV-C treated liquid egg products from the untreated ones when UV exposure is shorter than 25 min. And no difference could be detected when the UV-C processed egg products are cooked or used in egg preparations, such as mayonnaise,

Table 5 Viscosity in mPa.s of egg fractions submitted to heat or UV-C treatments. Treatment

Egg white

Whole egg

Egg yolk

Untreated UV 5 min UV 10 min UV 15 min UV 20 min UV 25 min UV 30 min Pasteurized

8.83 ± 0.44ab 7.07 ± 0.35c 7.77 ± 0.38cd 8.04 ± 0.33ad 8.14 ± 0.41ad 8.20 ± 0.42ad 9.05 ± 0.44b 19.44 ± 0.81e

11.26 ± 0.56a 7.10 ± 0.36b 7.79 ± 0.39bc 8.49 ± 0.42cd 8.93 ± 0.41de 9.54 ± 0.35ef 10.11 ± 0.51f 13.83 ± 0.64g

20.20 ± 1.01a 23.44 ± 1.17b 24.16 ± 1.21bc 24.88 ± 1.22bcd 25.51 ± 1.26bcd 26.12 ± 1.19de 26.94 ± 1.35e 24.07 ± 1.24bc

Values with different superscripts within a column are significantly different (P b 0.05), as determined by the Tukey's test at the 95% confidence level.

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