Abstract: The effect of superficial treatment with taxifolin solution (1 g L-1) in combination with modified atmosphere packaging (80%O2/20%CO2) on the sensory quality and instrumental color characteristics of chilled beef was studied. The combination of modified atmosphere packaging and taxifolin treatment of beef (TMA beef) preserved beef colour bright and lightly red up to the 12 days of storage at 0°C (18 days post mortem). Slight increase of sensory evaluated odor scores of TMA beef was established at the 18d post mortem. The sensory evaluated taste scores varied from 5.00 to 4.50 during whole experimental period. After 12 days of storage at 0°C the Lightness of the color (L*) values of beef trimmings increased with 3.8% and those of beef knuckles did not change significantly (*p>0.05). The red colour component (a*) of TMA beef decreased with 5.4 and 8.2% for beef trimmings and beef knuckles, respectively. Similar tendency was established for the yellow color component (b*). The chroma (C) of TMA beef did not change significantly (*p>0.05) and the hue angle (H) decreased with approximately 5.0%. The results obtained showed, that the TMA samples had higher SEC scores and better L*, a*, b*, C and H values in comparison with the other beef samples. The combined application of taxifolin treatment and modified atmosphere packaging improved the sensory quality, muscle color and color stability of chilled beef.
INTRODUCTION
Shelf life is an important issue for producers of fresh meat. Supermarkets and consumers ask for long shelf life as well as a good quality throughout the entire shelf life period. The predominant reason for meat shelf life is microbial spoilage activity (Koch et al., 2009). The micro-organisms can cause discoloration, off-odours, off-flavours, gas formation and/or changes in texture (Koutsoumanis et al., 2006). Nevertheless, if the meat temperature is between minus 2 to 0°C and the total microbial count of the packed meat is <105cfu g-1 can expect a very low microbial activity (Abd El-Rhaman et al., 2007). Therefore, there is not always a clear correlation between sensory acceptability and bacterial count (Koch et al., 2009).
On the other hand, color significantly influences on consumer purchasing decisions because discoloration is considered indicative of product spoilage (Jeremiah et al., 1972). The ability of myoglobin (Mb) to oxidase or to form bright red oximyoglobin (OMb) during meat marketing and to save its stability is different for the various muscles. The color stability decreases when the term of meat refrigeration prolongs. The decreasing of color stability is due to the OMb layer becomes thin and more rapid increasing of the MetMb layer (Renerre and Labas, 1987). The dynamics of the Mb layers during the beef bright-red color formation may be explained by their inherent biochemical characteristics to consume the oxygen and with reduction capacity of meat (Limsupavanich et al., 2004). There are some reviews on the oxygen consumption and NADH regeneration and their impact on the metmyoglobin (MetMb) reduction (Bekhit and Faustman, 2005; Mancini and Hunt, 2005; McMillin, 2008). The package type can influence red colour perception (Mancini and Hunt, 2005). The consumer preference for bright red beef over wrapped in polyvinyl chloride (PVC) might slow industry’s move toward central packaging such as Modified Atmosphere Packaging (MAP) and vacuum-packaging (Carpenter et al., 2001). High-oxygen MAP systems which have atmospheres of about 30%CO2 and up to 70%O2 were used to both extend the color stability and delay microbial spoilage of display-packaged meat (Robertson, 1993). Although both the color stability and the spoilage time were approximately doubled by high-oxygen MAP, this extension in shelf life is not wholly adequate for many commercial purposes (Robertson, 1993). The beef surface color was not considered as red after more than 8 days of storage at 0-4°C (Jakobsen and Bertelsen, 2000). The mixtures of 75-80%O2 with 25-15%CO2 were found as most effective for beef MAP. However, the off-odor and rancid taste are found in some MAP beef samples (John et al., 2004). Oxygen-enriched MAP represents an important means to stabilize meat color but could lead to a lipid oxidation development and thus influencing the product acceptability and safety (Ferioli et al., 2008).
When the modified atmosphere contains 70%O2/30%CO2 the bright-red color is kept during few days, only (Sorheim et al., 1999). Better color stability has been established in antioxidant treated meat (Formanek et al., 2003). The application of ascorbat/citrate (1:1) combination had more effective antioxidative action in comparison with rosemary extract when the beef was packed in high-oxygen atmosphere (Lund et al., 2007). The use of combination of rosemary/vitamin C reduced significantly the MetMb formation, inhibited the lipid oxidation and micro-organism growth and prolonged the shelf life with ten days to 20 d of storage (Djenane et al., 2003). The treatment with irradiated fitic acid significantly inhibited lipid oxidation and increased red color component (a*) of fresh meat during storage at 4°C (Park et al., 2004).
Many reports showed that flavonoids act as antioxidants and protected various cell types from oxidative stress-mediated cell injury. A comparison of cytotoxicity of some flavonoids toward cultured normal human cells showed that the taxifolin is very slightly toxic for human lung embryonic fibroblasts and human umbilical vein endothelial cells (Matsuo et al., 2005). The benefits of taxifolin application to sausages processed with mechanically deboned poultry meat (Semenova et al., 2008) and an improvement of the sensory quality and color properties of chilled salmon (Ivanov et al., 2009; Balev et al., 2009) were discussed during the last few years. The literature data for inhibition of oxidative processes of chilled beef using combination of taxifolin and MAP were not found.
The objective of the present study was to establish the possibilities for improving the sensory quality and colour stability of beef by superficial treatment with taxifolin solution in combination with MAP (80%O2/20%CO2).
MATERIALS AND METHODS
Materials and experimental design
Meat: The beef was supplied by the Unitemp Ltd., Voyvodinovo village, district
Plovdiv (Bulgaria) during the 2009. The carcass quarters LOT: L0801300201 were
imported from Poland. The carcasses were deboned and sorted on the 6 d post
mortem. The surface of the beef cuts was treated by spraying with taxifolin
solution (1g L-1). The meat temperature during the superficial treatment
was 3.2°C.
Samples were strained off for 60 min at 1.2°C, after that were packaged in transparent polymer bags with sizes 10/28 cm. The temperature of air in the premises for packaging was 7.5°C. The packaged samples were put into plastic boxes, labeled and stored at 0±0.5°C before analysis. The packaged samples had temperature of 6.3°C and pH values of 5.65 and 5.71 for beef trimmings and beef knuckles, respectively.
Experimental design: The experiments were carried out with eight samples, as follows: control sample CA-beef trimmings 90/10%, air-packaged and not treated with taxifolin; sample MAA-beef trimmings 90/10%, packaged in a modified atmosphere consisting of 80%O2/20%CO2 (MAP) and not treated with taxifolin; sample TA-beef trimmings 90/10%, air-packaged and treated with taxifolin solution (1 g L-1); sample TMAA - beef trimmings 90/10%, MAP and treated with taxifolin solution (1 g L-1); control sample CB - beef knuckles with bones, air-packaged and not treated with taxifolin; sample MAB - beef knuckles with bones, MAP and not treated with taxifolin; sample TB - beef knuckles with bones, air-packaged and treated with taxifolin solution (1 g L-1) and sample TMAB - beef knuckles with bones, MAP and treated with taxifolin solution (1 g L-1). All experimental samples were stored at 0±0.5°C for 12 days.
The analyses were carried out on 6d post mortem (first day of the experiment); 9 days post mortem (after three days of storage), 12 days post mortem (after six days of storage) and 18 days post mortem (after twelve days of storage)
Taxifolin solution: Taxifolin is a flavonole. Its IUPAC name is (2R)-2-(3,4- dihydroxyphenyl)-3,5,7-trihydroxy-chroman-4-one. It is known with different names such as: 2R, 3R-dihydroquercetin; 3,3',4',5,7-pentahydroxiflavonon or 2,3-dihydro-3,3',4',5,7- penta-hydroxi-flavon. The taxifolin CAS # is 480-18-2. Its empiric formula is C15H12O7. The powder concentrate of taxifolin, extracted from Siberian larch (Larix sibirica Ledeb) and produced by the company Flavit Ltd., Pushtino (Russia) was used. The concentrate contained: 96% dihydroquercetin, 3% dihydrokempferol and traces of naringenin.
One gram of taxifolin was diluted in 50 cm3 96% ethyl alcohol and filled up to 1 dm3 with 950 cm3 twice distillated water. Fifty kilogram beef was treated with 1 L taxifolin solution.
Modified atmosphere packaging: Some samples were MAP (80%O2/20%CO2), according recommendations of Mancini and Hunt (2005). The packaging machine Yang SR1, model Polaris VAC, Ductto (22100 Yang, Como via al Bassone 30, Italy) was used. The beef cuts were packaged in polymer pads (ClearFresh®), wrapped in folio with anti-frog effect (PP dan, France) which is 100% barrier for gases and moisture.
Methods
Sensory analysis: For the sensory analysis, a seven member expert
panel from Department of Meat and Fish Technology of the University of Food
Technologies, Plovdiv (Bulgaria) was used to evaluate roast beef flavor, aromatics,
feeling factors, basic taste with proved taste and color of the raw meat. All
the panelists had more than 10 years of experience in Spectrum descriptive flavor
analysis and underwent ballot development and training sessions using beef roast
control samples and beef roasts containing antioxidant.
| Table 1: | Descriptive characteristics of beef color, odor and taste
according hedonistic scale |
In the squares below the drawings mark off the expression which the best fix your attitude to the examined raw and roast beef samples
The panelists participated in six training sessions and underwent performance testing as specified in guidelines developed by Wheeler (1982). The beef roasts were evaluated by the panelists for aromatics (cooked beef/broth, cooked beef fat, chemical taste, serum/bloody and plum/prune); feeling factors (astringent, metallic and chemical burn); basic tastes (salt, sour, bitter and sweet) and texture attributes (springiness, juiciness, hardness cohesiveness and denseness). The roast beef samples were also scored using 1-5 scale (Larick and Turner, 1990). The panelists were passed the triangular test for differentiation of fresh and rancid meat taste, odor and color (Meilgaard et al., 1999). Examination of beef samples was done after the packs opening. The chilled to 0°C samples were put in aluminum foil packs and grilled for 20 min at 200-250°C. The records of the panelists were filled in the check sheets using hedonistic scale with five examination marks (Table 1).
Instrumental colour analysis: Colorimeter Konica Minolta model CR-410 (Konica Minolta Holding, Inc., Ewing, New Jersey, USA, purchased by Sending, Inc., Tokyo, Japan) was used to evaluate the lightness of the color (L*), red color component (a*), yellow color component (b*), chroma (C) and hue angle (H) (Brewer and Wu, 1993).
Statistical analysis: Nine repetitions (n = 9) for each sample were carried out. Data were subjected to analysis of variance (ANOVA) (Draper and Smith, 1998). The Fischer’s test with significant difference at p≤ 0.05 was used to compare sample means. Significant differences between means less than 0.05 were considered statistically significant (Kenward, 1987).
RESULTS
Sensory evaluation
Sensory Evaluated Color (SEC): The SEC scores of samples CA,
CB, TA, TB, MAA and MAB
decreased steadily during the 12 days of storage at 0±0.5°C (Fig.
1). In contrast to them, the SEC scores of samples TMAA and TMAB
stayed very high during whole storage period and their averages did not
differ significantly (*p>0.05). The greater decrease of SEC was found in
the control samples CA and CB. After 12 days of chilled
storage SEC scores of samples CA and CB decreased with
69.4% and 79.9%, respectively. Similar tendencies of colour changes were found
in samples TA and TB (Fig. 1). After
12 days of cold storage, the SEC scores of these samples decreased with 54.3
and 52.2%, respectively. Slight decrease of the SEC scores of samples MAA
and MAB was also found - with 25.0 and 22.9%, respectively (Fig.
1). According to the results obtained, TA and TB samples
could be considered as acceptable for consumers up to the 3d of chilled storage
(9d post mortem) and samples MAA and MAB-up to 6d of storage
(12 post mortem). The SEC of samples TMAA and TMAB remained
very satisfactory during whole period of refrigeration storage (Fig.
1). Therefore, according to this parameter they could be considered as acceptable
for consumers up to the 12d of chilled storage (18 post mortem).
Sensory Evaluated Odor (SEO): The changes in SEO of all studied samples showed similar trends to those found for SEC (Fig. 2). It was found that odor of roasted beef samples CA, CB, TA, TB, MAA and MAB showed trends to deterioration during the storage at 0±0.5°C. The most significant decrease of SEO scores was established for samples CA and CB on the 18 days post mortem - with 73 and 80%, respectively. Similar tendency was found for samples TA and TB, which SEO scores decreased with 53 and 54%, respectively after 12 days of cold storage (Fig. 2). Better preservation of beef odor was established for MAP samples.
| Fig. 1: | Changes in the Sensory Evaluated Color (SEC) of beef during
storage at 0±0.5°C |
| Fig. 2: | Changes in the Sensory Evaluated Odor (SEO) of beef during
storage at 0±0.5°C |
| Fig. 3: | Changes in the Sensory Evaluated Taste (SET) of beef during
storage at 0±0.5°C |
The SEO scores of MAA and MBB samples did not change significantly (*p>0.05) after 6 and 3 days of chilled storage, respectively. After that period odor deterioration was also established. The best results for SEO were established for samples TMAA and TMBB. After 12 days of cold storage the SEO scores of these samples did not change significantly (*p>0.05) and were close to the maximum values of 5.00.
Sensory Evaluated Taste (SET): The results obtained (Fig. 3) showed that, the SET scores of samples CA, CB, TA, TB, MAA and MAB decreased steadily during the chilled storage. The most significant decrease of SET scores was found in control samples CA and CB (18 d post mortem) - with 73 and 79%, respectively. Similar tendencies of SET changes were found in samples TA and TB. At the end of the experiment (18days post mortem) the SET scores of these samples decreased with 48 and 52%, respectively. Thus they reach values in the range of 2.2 to 2.4 indicating that their taste was unacceptable for the consumers.
| Table 2: | Changes in the instrumental color characteristics of beef
during the storage at 0±0.5°C |
Slight decrease of the SET scores of samples MAA and MAB during the cold storage was also found - with 30.0 and 15.0%, respectively (Fig. 3). It was established that the SET scores of TMA samples did not change significantly (*p>0.05) during the chilled storage. Therefore, according to this parameter TMAA and TMAB samples could be considered as acceptable for the consumers up to the 12 days of chilled storage (18 post mortem).
Instrumental color: The results from instrumental color analysis (Table 2) showed that the L* values of all studied samples varied between 33.38 and 45.67, with average standard deviation of±0.37. After 12 days of refrigerated storage L* values of samples CA, CB, TA, TB, MAA and MAB decreased significantly (*p>0.05). The most significant decrease of L* was established for control samples CA and CB - with 19.3 and 16.0%, respectively. During the first 3 days of chilled storage L* values of TA and TB samples increased slightly and after that decreased steadily to the end of the experiment. A slight decrease of L* measures of samples MAA and MAB was also established - with 4.6 and 4.3%, respectively. In contrast to the other beef samples, L* values of TMAA increased during beef cuts storage with 3.8% and those of TMAB did not changed significantly (*p>0.05).
The results obtained for red (a*) and yellow (b*) color components (Table 2) showed a tendency towards decreasing for all studied samples. The most significant (*p<0.05) decrease of a* values was established for TA and TB samples - with 22.9 and 25.9%, respectively. Similar tendency of decreasing was found for the b* values. In contrast with a*, the most significant decrease of b* was established for samples CA and CB - with 28.0 and 24.7%, respectively. The slightest changes of a* and b* were established for TMAA and TMAB samples.
Heterogeneous changes of chroma during the chilled storage of experimental samples were found (Table 2). The C values of samples CA, CB, TA and TB decreased with approximately 49±1%. Different tendencies were established for MAP samples. The C measures of MAA, MAB, TMAA and TMAB samples did not change significantly (*p>0.05) during the chilled storage.
The hue angle (H) measures of the studied samples varied between 37.48 and 51.77 (Table 2). It was established that H values of samples CA, CB, TA, TB, MAA and MAB decreased with 22 to 30% during the chilled storage. Slight decrease of H measures of samples TMAA and TMAB was also found - with 4.1 and 5.6%, respectively.
DISCUSSION
The results obtained showed that the SEC of the control samples CA and CB became unacceptable even as early as 9 days post mortem (Fig. 1). Similar results were reported by Abd El-Rhaman et al. (2007) who found an unacceptable color and off-odor after 5 days of storage at 4°C of air-packaged beef. It is well known, that the cherry-red color of muscle surface is determined by oxygen consumption of muscle sells, partial pressure of oxygen on muscle surface and extend of myoglobin oxidation (O`Keeffe and Hood, 1982). The relatively higher SEC scores of samples MAA, MAB, TMAA and TMAB could be explained by the fact that the high-oxygen MAP contributed for muscle oxymyoglobin stabilization. Besides, the lower temperature increased myoglobin water solubility, accelerated lipid oxidation and inhibited enzyme activity (Bendall and Taylor, 1972). On the other hand, the spoilage caused by lactic acid bacteria produced surface discoloration development of value-added, high-oxygen modified-atmosphere packaged beef steaks (Vihavainen and Björkroth, 2007). It was established, that the superficial treatment of MAP beef with taxifolin solution causes minimization of the beef SEC changes at the conditions of this experiment. The color of samples TMAA and TMAB was preserved bright, fresh and even brightly-light red. This is one favorable prerequisite for heightened consumer demand during the retail of chilled beef. The antioxidant treatment of MAP beef pities contributed for colour preservation during the storage at 4°C. The results obtained by these authors were in agreement with our data for the SEC changes during cold storage of MAP beef samples.
The results obtained for SEO of MAP beef (Fig. 2) were in agreement with the findings of Konopka and Grosch (1991), who established worm-over flavor development in high-oxygen MAP (80%O2/20%CO2) beef steaks after 6 days of refrigerated storage. According to the authors, the worm-over flavor appears as a result of lipid oxidation processes. Therefore, the antioxidant treatment of high-oxygen MAP beef could prevent worm-over flavor development by delaying the lipid oxidation. Such statement is in agreement with our results (Fig. 2) for SEO of taxifolin treated MAP beef samples. Jakobsen and Bartelsen (2000) and Jayasingh et al. (2002) also established a lipid oxidation development during chilled storage of high-oxygen MAP meat. They found relation between worm-over flavor appearance and antioxidant concentration. It is known that the consumers susceptible to worm-over flavor did not accept the high-oxygen MAP beef (Jakobsen and Bartelsen, 2000; Jayasingh et al., 2002). Moreover, Vihavainen and Björkroth (2007) found that the lactic acid bacteria initiated spoilage processes produced the buttery off-odors development in value-added, high-oxygen modified-atmosphere packaged beef steaks. Therefore, the modified atmosphere consisting of 50-80% oxygen is proposed for beef steaks storage (Clausen, 2004).
The taste sensory analysis indicated that the SET of MAP beef was acceptable for the consumers up to the 7 days of chilled storage (12 post mortem). Our results (Fig. 3) were in agreement with the findings of Ferioli et al. (2008) who established taste deterioration during the chilled storage of oxygen-enriched atmosphere packaged raw beef. According to the authors the taste changes of chilled beef were influenced by the lipid and cholesterol oxidation development. Therefore, it could be assumed that the application of antioxidants for high-oxygen MAP beef will contribute to taste preservation. This hypothesis was confirmed by the results for the SET of samples TMAA and TMAB. It could be assumed that the sensory evaluated color, odor and taste of chilled beef were preserved most effectively by the combined application of taxifolin treatment and MAP.
The changes of L*, a*, b*, C and H established in the present study (Table 2) could be explained with the lipid oxidation development of oxygen-enriched atmosphere packaged raw beef (Ferioli et al., 2008) and oxymyoglobin layer formation on the beef cuts surface (Mancini and Hunt, 2005). According to Mancini and Hunt (2005) the oxidative process and related color changes are influenced mainly by the oxygen content of MAP beef. High-oxygen atmospheres (80% O2) promote pigment oxygenation and therefore, prolong the time before metmyoglobin is visible on the muscle surface. The drawback to high-oxygen MAP is, although it maintains redness during storage, rancidity often develops while color is still desirable (Jayasingh et al., 2002). Jakobsen and Bertelsen (2000) reported that while oxygen levels higher than 20% were necessary to promote meat color, package oxygen contents higher than 55% did not result in additional color stabilizing benefits.
The initial increase of L* values of TA and TB samples (Table 2) could be explained with the ethanol-induced coagulation of proteins situated on the beef cuts surface (Olsen and Osterud, 1987). In the present study, the ethanol was used as solvent for preparing of taxifolin solution. Coagulation of beef surface proteins could modify the meet light reflection and thus to increase the L* values (Schubert and Finn, 1981). Similar effect has been observed previously in chilled stored salmon superficially treated with taxifolin solution (Balev et al., 2009).
The results obtained by instrumental color analysis (Table 2) were in accordance with the data obtained by the sensory analysis (Fig. 1- 3). Similarly, in evaluating veal color, Hulsegge et al. (2001) reported that visual color scores of veal carcasses (Rectus abdominis) were moderately correlated with L* and a*. In the present study, the TMAA and TMAB samples had higher SEC scores and L*, a*, b*, C and H values in comparison with the other beef samples.
CONCLUSIONS
The obtained results indicated that the superficial spraying with taxifolin solution (1 g L-1) of air-packaged beef was not effective for preservation of specific fresh beef color, taste and aroma during storage at 0°C. The sensory quality of these samples was unacceptable at the 9 post mortem. The superficial treatment of MAP beef with taxifolin solution minimized the color changes at the conditions of the experiment. The sensory evaluated color of these samples was preserved bright, fresh and even brightly-light red. Packing of chilled beef cuts in high-oxygen MAP in combination with taxifolin treatment had stabilizing effect on instrumental color characteristics. The combined application of taxifolin treatment and MAP improved the sensory quality, muscle color and color stability of chilled beef.
ACKNOWLEDGMENT
The authors expresses their gratitude to the technological team of the company Unitemp Ltd, Voyvodinovo, Plovdiv region, as well as the management of the company Vitalife Ltd., Sofia for the co-operation and support rendered.