Effect of Grape (Vitis vinifera) Seed Extract on the Physico-Chemical, Microbial and Sensory Characteristics of Chevon Nuggets

Meat and other ingredients
 
Deboned goat meat was obtained from local market, packed in low density polyethylene bags and kept under frozen storage at -18±2oC for the subsequent use. Frozen meat was thawed at 4±1oC for 24 hrs before use and cut into small pieces before grinding. Refined salt (Tata Chemicals Ltd., Mumbai), refined wheat flour, spice mix ingredients, flaxseed powder, skim milk powder (Anikspray, Nutrica) and grape seed were procured from local market of Jaipur. Fine pastes of onion, garlic and ginger in the ratio 3:1:1 were used for preparation of chevon nuggets. Chemicals and media used for analysis of product were procured from standard firms like Sigma, Mark, SRL and Hi-media etc.
 
Preparation of chevon nuggets
 
Frozen chevon was partially thawed overnight, cut into small cubes and double minced with meat mincer. Meat emulsion was prepared in a bowl chopper (Hakimi, India). Pre-weighed quantity of minced chevon, salt, sodium tripolyphosphate and sodium nitrite were added and chopped for about 2-3 minutes. It was chopped again for 2 minutes after the addition of ice flakes. Animal fat was slowly incorporated while chopping till it was completely dispersed in the batter. Refined wheat flour, condiment paste, dry spice mix and other ingredients viz: skim milk powder, flaxseed powder, sugar, GSE were added. Chopping was continued till uniform dispersion of all the ingredients and desired consistency of the emulsion was achieved. Weighed quantity of emulsion was taken and filled in stainless steel mould. Mould was covered with lid and tied with thread and steam cooked for 34 minutes. Core temperature of cooked blocks was recorded by using probe thermometer that should reach to 73°C.  Chevon meat block obtained was sliced and cut into pieces to get nuggets and stored at -18±2°C. At 15 days intervals sample were removed for analysis of physico-chemical, microbiological and sensory properties. The analysis was continued for 30, 45 and 60 day in frozen storage.
 
Analytical procedure
 
Extract preparation
 
The dried seed of grape seed was air-dried in hot air oven at 50°C for 2 hrs, followed by grinding in grinder [Uno (mx-140), Groupe SEB India pvt. Ltd] and sieving. Extracts from dried powdered seeds were extracted with 70% ethanol in ether extraction assembly. The color of the extracts was dark brown. The extract was collected and concentrated under reduced pressure in a rotary vacuum evaporator (Labconco corporation, USA) until semi solid consistency was obtained. The semisolid mass was air-dried to obtain solid mass. Powdered substances were reconstituted with the same solvent as used for extraction to make 5% stock solutions (0.5g of dried extract /10 ml) and stored under refrigeration at 4°C for further use.
 
In vitro antioxidant assays
 
The antioxidant activity of the extract was evaluated by the phosphomolybdenum method (Prieto et al., 1999). The total phenolic content was determined using spectrophotometric methods (Singleton et al., 1999) and total flavonoid content was determined by the aluminum chloride colometric assay (Meda et al., 2005).
 
Physico-chemical parameters
 
The determination of TBARS value was based on the procedure of Witte et al., (1970) and FFA% value was estimated as per Koniecko (1979).
 
Microbiological examinations
 
Total plate count, psychrophilic count, coliform count and yeast & mold count were determined following the methods described by APHA (1984).
 
Sensory evaluation
 
There were 7 experienced taste panel members consisting of faculty members and postgraduate students of the department and the institute, evaluated the sensory attributes viz. appearance, flavor, texture, juiciness and overall acceptability of treatment and control using 9 point hedonic scale (Wichchukita and O’Mahonyc, 2010).
 
Statistical analysis
 
Data hence obtained through the experiments were analyzed as per Snedecor and Cochran (1994) using Statistical Software Packages (SPSS 16.0).

Assessment of in vitro antioxidant activity of grape seed extract
 
Antioxidant ability assays, total phenolic and flavonoid content 
 
Total antioxidant capacity of GSE was found to be 312.06±1.69 μg ascorbic acid equivalents at 100 μg/ml. Many studies have reported a positive correlation between phenolic compounds in plants and their antioxidant activities showing the importance of phenolic compounds as antioxidants (Fu et al., 2011). The antioxidant activity of grapes has been positively associated with their phenolic composition such as anthocyanins, flavonols, flavan-3-ols, procyanidins and phenolic acids (Fujii et al., 2007; Kedage et al., 2007; Pazos et al., 2006). The total phenolic content for the ethanolic extracts of GSE was found to be 190.34±2.26 mg of gallic acid/g. Nirmala et al., (2011), sofi et al., (2016), Baydar et al., (2004) and Li et al., (2008) reported total phenolic content of GSE was 196, 1.23 and 627mg GAE/g respectively depending on concentrations and solvent medium. The total flavonoid content of GSE extract was found to be 83.43±2.36 mg rutin/g. Further sofi et al., (2016) and Jayaprakasha et al., (2001) reported total flavonoid content in grape seed extract was 1.662 and 50.50 respectively, depending on the concentrations and solvent medium.
 
Physico-chemical properties
 
Thio-barbituric acid reacting substances
 
In this study, treatment had significantly lower (P<0.05) TBARS than control products throughout frozen storage period (Table 1). The mechanism of the protective effect of GSE on lipid oxidation due to the presence of a number of oligomer procyanidins, such as catechin and epicatechin (Yilmaz et al., 2004). The results of the present investigation were in agreement with findings reported by Cagdas et al., (2015) and Ei-zainya et al., (2016), who observed a reduction in TBA value in chicken nuggets and beef sausage respectivily. General increase in TBARS values might be attributed to the lipid oxidation and the production of volatile metabolites. This was in agreement with the findings of Das et al., (2008), Sayagao-Ayerdi et al., (2009), Alabdulkarim et al., (2012), Teruel et al., (2015) and Nath et al., (2016) during frozen storage of different meat products.
 

 
Free fatty acid % value
 
Chevon nuggets treated with GSE had significantly lower (P<0.05) FFA% value than control throughout the storage (Table 1). An increase in FFA% values in meat products during storage because of lipase activity has been reported by Das et al., (2008) who also found a similar increase in FFA values during frozen storage in goat meat nuggets.
 
Microbiological properties
 
Addition of GSE significantly (P<0.05) influenced the total plate count (TPC) of chevon nuggets during storage. At the end of storage period mean of the treatment (2.35 log cfu/g) have significantly lower TPC than the control (2.66 log cfu/g) (Table 2). Throughout the storage period, TPC of treatment was lower than control. Similar findings were observed by Das et al.,  (2008) and Nath et al. (2016) during storage in goat meat nuggets and chicken nuggets respectively.
 

       
The psychrophilic count were not detected on zero day in both treatment and control but they appeared 15^th day and to be significantly increase throuhout the storage period. At the end of storage period mean of the treatment (1.57 log cfu/g) has significantly lower psychrophilic count than the control (1.84 log cfu/g) (Table 2). Similar findings were observed by Biswas et al., (2004) and Nath et al., (2016) in different meat products. The reduction of total psychrophilic counts of treatment was due to the antimicrobial activity of GSE (Ahn et al., 2004).
         
Yeast and molds were not detected till 30 day during frozen storage period in both control and antioxidant extract treated chevon nuggets, but they appeared on the 45^th day of storage in both control and treatment. The significant effect of natural antioxidants treatment on the yeast and mold count of the chevon nuggets. At the end of storage period treatment (0.57 log cfu/g) have lower yeast and mold than the control (0.71 log cfu/g) (Table 2). Similar findings was observed by Nath et al., (2016) in chicken nuggets during frozen storage. Coliform were not detected in the treatment as well as control during storage period.
 
Sensory characteristics
 
The flavor score of chevon nuggets during frozen storage was significantly (P<0.05) affected by both GSE and storage period (Table 3). The chevon nuggets treated with GSE showed significantly (P<0.05) higher flavor score than control. A decrease in flavour scores during storage was also reported by Das et al., (2008), Alabdulkarim et al., (2012) and Nath et al., (2016) in different meat products. Texture scores decreased during storage. A decrease in texture scores of the products was expected because of proteolytic and lipolytic changes during storage. With increase in storage period, decrease in juiciness scores was noticed for control and treatment. During entire storage, control products were observed with significant decrease (P<0.05) in overall acceptability scores at each interval of storage period. Control product had significantly lower (P<0.05) scores than treatment products throughout the storage period (Table 3). During the storage period consistence decrease in overall acceptability scores treatment and control was observed. The decrease in overall acceptability scores of the products during storage has been reported by various researches such as Das et al., (2008) and Nath et al., (2016) in goat meat nuggets and chicken nuggets respectively.