Antioxidant Activity and Quality Attributes of Ostrich Meat Nuggets as Affected by Addition of Broccoli Powder

INTRODUCTION

     Antioxidants are compounds that can delay or inhibit the oxidation of lipids or other molecules by inhibiting the initiation or propagation of oxidizing chain reactions. The antioxidants activity of phenolic compounds is mainly due to their redox properties, which can  play an important role in adsorbing and neutralizing free radicals, quenching singlet and triplet oxygen or decomposing peroxides (Muchuweti et al. 2007). The synthetic antioxidants,i.e. butylated hydroxyl anisole (BHA) and butylated hydroxyl toluene (BHT) are widely used as food additives and very cost effective given a high stability. The use of BHT and BHA in food has been decreased due to their suspected action as promoters of carcinogenesis or possible toxic as well for the general consumer rejection of synthetic food additives (Namiki, 1990). Several studies indicated that the use of synthetic antioxidants has begun to be restricted because of their health risks and toxicity (Farag et al. 2006).

 

 

 

       Natural antioxidants are significant food constituents and serve a number of functions in a human body. High contents of antioxidants may be found in fruits and vegetables as well as in their processed products.Their action is chiefly  based on the neutralization of free radicals and on the prevention from oxidation processes (Sikora et al. 2008). Nowadays, there is a strong need for effective antioxidants from natural sources to prevent deterioration of fats and oils (Samarth et al. 2008).

 

      The replacement of synthetic antioxidant by natural one may have benefits due to health implications and functionality such as solubility in both oil and water (Hagerman et al. 1998; Reglero et al. 1999). Vegetable materials contain many compounds with antioxidant activity. Some plants have been studied as sources of potentially safe natural antioxidants for the food industry, various compounds have been isolated, many of them being polyphenols (Hagerman et al. 1998). Some components of extracts isolated from natural sources such as oilseeds, spices, fruits and vegetables have been proven in model systems to be as effective antioxidants, as synthetic antioxidant  (Melo et al. 2005), and it is considered important to increase the antioxidant intake in the human diet and one way achieving this is by enriching food with phenolics. The use of natural antioxidants to stabilize meat has gained much attention from consumers because they are considered to be safer than synthetic antioxidants (Jung et al. 2010) such as BHT, TBHQ and BHA.

 

    Natural antioxidants have the ability to increase the antioxidant capacity of the plasma and reduce the risk of certain diseases such as cancer, stroke and cardiovascular diseases (Chanda and Dave, 2009). It has also been reported that these natural antioxidants, especially of plant source, have greater application potential for consumer's acceptability, palatability, stability and shelf life of meat products (Jung et al. 2010).

 

    Broccoli (Brassica oleracea L.) is rich in both nutritional antioxidants, vitamin C and E and minerals and non nutritional antioxidants carotenoids, nitrogen-sulphur derivatives (glucosinlates and isothiocyanates), and phenolic compounds, particularly flavonoids (Faller and Fialho, 2009; Dominguez-Perles et al. 2012 ), which possess both antioxidant and anticancer activities (Podsedek, 2007, Monero et al., 2010). Brassica, cruciferous family (cauliflower, broccoli, cabbage, and brussels sprouts) is known to be a rich sources of antioxidants (Mukherjee et al. 2008; Kim et al. 2013). Also, Bhandari and Kwak (2014) reported that broccoli is a source of health promoting phytochemicals .

 

     Ostrich meat is recognized as a valuable product of high nutritive and dietetic value making these birds important for many livestock industries (Cooper et al. 2008). Internationally, ostrich meat has become an acceptable red meat and is readily found as either fresh meat or at restaurants in many countries. Initially, ostrich was assumed to be a healthy red  meat containing low cholesterol (Sales, 1998), low sodium  collagen and high polyunsaturated fatty acids and iron ,although by now it is accepted that ostrich has cholesterol levels similar to other lean meat types and recommended as an alternative to other types of red meat (Hoffman and Mellett, 2003; Zarasvand et al. 2012).

 

       The addition of antioxidants to processed meats is often carried out to counteract the negative effects of processing aids. However, may be desirable to replace these conventional antioxidants with natural antioxidative substances. Recently, various studies reported the incorporation of the vegetables in comminuted meat products with improved quality, health benefits (Bhosale et al., 2011; Mendiratta et al. 2013) and reduced production cost besides their inherent functional properties (Viuda-Martos et al. 2010).

 

     Natural antioxidants are in great demand today due to both consumer preference and health concerns associated with the use synthetic antioxidants.  Therefore, the objectives of this study were evaluate the antioxidant potential of broccoli powder in ostrich meat nuggets comparing with BHA and determined the quality attributtes of the ostrich nuggets during refrigerated storage at 4ºC at 15 day.

 

MATERIALS AND METHODS

Materials:

   Fresh broccoli (Brassica oleracea) was purchased from a local market, Alexandria, washed with clean water  and sliced into small pieces. The sliced broccoli was dried in hot air oven at 60ºC until drying (24 hrs). The dried broccoli was ground in home mixer to make fine powder and packed in polyethylene bags and kept at refrigerator until used. 

    Fresh ostrichmeat was obtained from the Egyptian Company of Ostrich breeding, Cairo, Egypt. The carcass were hot deboned and meat was chilled  overnight in refrigerator at 4ºC and packed under vacuum in polyethylene bags and quickly brought   in ice box to the laboratoty and stored under frozen condition (-18ºC) till further use.

 

   Other additivs used were spices mix (white pepper, red pepper, black pepper, nutmeg, cumin), sodium chloride, refined vegetable oil, condiments (garlic powder, onion powder), refined wheat flour and whole egg liquid were obtained from supermarket of Tanta City, Egypt.

BHA was purchased from Sigma (st. Louis. MO.USA). Folin-Cioculteau reagent was obtained fromGerbsaur Chemical Co (Germany). Gallic acid (98%) was purchased from Aldrich Chemical Co. Ltd., England.

 

Methods:

Preparation of ostrich meat nuggets:

 Ostrich meat nuggets were prepared as per the formulation given in Table (1).

 

 

Table (1) : Formulation for ostrich meat nuggets prepared with broccoli        powder (Bp) and butylated hydroxyl anisole (BHA)

     

  Ostrich meat nuggets were prepared according to methods of Banerjee et al. (2012).The deboned frozen ostrich meat nuggets was thawed for 12 h in refrigerator (4ºC), cut into small chunks and minced twice in a meat mincer (Moulinex) through 6 mm and 4 mm plates and then the  salt was added and chopped for 2-3 min with simultaneous addition of ice flakes. Refined sunflower oil was slowly incorporated while chopping till it was completely dispered in the batter. Condiment powder (onion and garlic), dry spice mix, refined wheat flour and broccoli powder at different levels (0, 2, 4, 6, 8% and BHA treatment) were added, and a control without broccoli powder was included as shown in Table 1.  Chopping continued till uniform dispersion of all the ingredients and desired consistency of the emulsion which was prepared in a bowl chopper to make a batter or during which the temperature was maintained below 12ºC.  The nuggets obtained was formed by hand and filled in polyethylene bags and the bags were electric sealed before storing at 4ºC in refrigerator for 15 day.

Analytical methods:

     Raw materials (fresh ostrich meat and dry broccoli powder) and refrigerated samples were evaluated for their proximate composition. Ostrich nuggets samples were evaluated for their chemical composition, physicochemical properties, antioxidant activity as well as sensory evaluation.

Proximate composition :

     Moisture was determined using air oven at 105ºC until constant weight , crude protein content was estimated using microKjeldahl procedure to determine the total nitrogen and multiply this value by the factor of 6.25; ether extract was performed in a Soxhelt apparatus using petroleum ether (40-60ºC) as a solvent and ash content was carried out by subjecting samples to pre-ashing, then complete the ashing in an electric muffle at 550˚C until constant weight.  All of them according to the method described by A.O.A.C. (2005). Total carbohydrates were calculated by difference. Thiobarbituric acid (TBA) as mg malonaldehyde/kg ostrich meat nuggets at zero time and during refrigerated storage at 4ºC for 15 day was spectrophotometrically determined at 532 nm using Specteronic JENWAY 6300 spectrophotometer as mentioned by Siu and Draper (1978).

Physicochemical analysis :

Cooking loss :

   Cooking loss was expressed as g/100 g and calculated by the weight difference between uncooked and cooked ostrich meat nuggets samples according to Barbanti and Pasquini (2005).

Cooking yield

The cooking yield of the nugget was determined according to the method of Santhi and Kalaikannan (2014). The value of cooking yield was expressed as percentage following the equation: freshly cooked sample weight at room temperature divided by the uncooked sample weight multiplied by 100.

              Cooking yield (%)=cooked weight/uncooked weight×100

Shrinkage :

     Diameter of raw and cooked ostrich nuggets were measured according to the method described by Berry (1993). Percent changes in diameter of sample were calculated as follows :

Diameter reduction (%) = Fresh diameter - Cooked diameter / Fresh diameter × 100

pH measurement :

     pH of ostrich meat nuggets was measured using Digital pH-meter ( JENWAY model 333 Research pH meter) after blending 15 g ostrich meat nuggets with 150 ml deionized water for 2 min (Xiong et al. 1993).

Preparation of sample extracts :

   Broccoli powder and ostrich nuggets extracts were obtained by extraction of samples with methanol. The samples (50 g) were crushed and  then extracted three times with 200 ml of the solvent  by stirring for 4 h at 40ºC. After filtration through a folder filter, the supernatants were joined and concentrated under reduced  pressure using a rotary evaporator until dryness (Rabaneda et al. 2003).

Determination of antioxidant compounds :

Total phenolic content :

   The total phenolic content (TPC) in broccoli powder and ostrich nuggets was estimated in the extract following the Folin-Ciocalteu method (Singleton and Rossi, 1965) and Heimler et al. (2005). The reaction mixture was composed of 0.1 ml extract, 7.9 ml distilled water, 0.5 ml of Folin-Ciocalteu's reagent and 1.5 ml of a 20% sodium carbonate anhydrous solution (added 2 min after the Folin-Ciocalteu's reagent). After initial mixing the opaque flasks were allowed to stand for 2 hrs. The O.D of the blue coloured samples was measured spectrophotometrically (JENWAY 6300) at 720 nm and  determined as gallic acid equivalents (GAE) and the values were  expressed as mg of gallic acid / g of sample.

Total flavonoids :

   Total flavonoids were analyzed according to the method described by Zhishen et al. (1999). The samples absorbance was measured at 510 nm on a spectrophotometer (JENWAY 6300) against the blank (distilled water) and catechol was used as standard reagent. The total flavonoids content was expressed as mg /100 g (dry weight basis).

Glucosinolates :

   Glucosinolates content was determined in broccoli powder as allyl isothiocyanate (mg/100g dry weight basis) by using titratable method as the procedure described the standard methods of A.O.A.C. (2000).

Antioxidant activity :  

DPPH radical scavenging activity:

   The ability to scavenge 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical by added antioxidants in the product was estimated by the method of Kato et al. (1988) with slight modifications. Fresh DPPH solution was prepared in ethanol before every measurement. In this method, about 5 g of sample was triturated with 20 ml of ethanol for 2 min. The contents were quantitatively transferred into a beaker and filtered through Whatman filter paper No 42. Then, 1 ml of the filtrate was mixed with 1ml of 0.1M Tris-HCl buffer (pH 7.4) and 1ml of DPPH reagent (250 μM) in test tubes. The content was gently mixed and then the absorbance in time, t= 0 min (t0) was measured at 517 nm using a spectrophotometer (JENWAY  6300). The sample tubes were also incubated at room temperature (27±1°C) under dark for measurement of absorbance in time t=20 min (t20). Ethanol was used as blank sample. Gallic acid (200-600 μM/ml) was used as a standard. The free radical scavenging activity was calculated as a decrease of absorbance from the equation:

Radical scavenging activity (%) = 100 - (At20 / At0) x 100

ABTS radical scavenging activity:

   The spectrophotometric analysis of 2,2– azino-bis (3-ethylbenzothiazline-6-sulphonic) ( ABTS+) radical scavenging activity was estimated according to method of Shirwaikar et al. (2006).This method is based on the ability of antioxidants to quench the longlived ABTS+ radical cation, a blue/green chromophore with characteristic absorption at 734 nm, in comparison to that of standard antioxidants. The ABTS was dissolved in water to a 7 mM concentration and potassium persulphate added to a concentration of 2.45 mM. The reaction mixture was left to stand at room temperature overnight (12-16 h) in dark to allow the completion of radical generation. Prior to use, the stock solution was diluted with ethanol to an absorbance of 0.70 at t0 (t = 0 min) and equilibrated at 3°C exactly 6 min after initial mixing. About 4.9 ml of ABTS working standard solution was mixed with 100 μl of sample extract/standard and absorbance was measured after 20 min (t20) at 734 nm. Gallic acid (50- 400 μM/ml) was used as a standard antioxidant. The ABTS+ activity was calculated by using following formula:

ABTS activity (%) = [(At0- At20)/At0] x 100.

Increased absorbance of the reaction mixture indicated higher reducing power of the sample extract.

Ferric reducing antioxidant power assay :

   Ferric reducing antioxidant power of the extracts was determined according to the method of Oyaizu (1986). Different concentrations of broccoli powder, ostrich nuggets which contained broccoli powder extracts and BHA nuggets were mixed with 2.5 ml of phosphate buffer (0.2 M, pH 6.6) and 2.5 ml of 1% (w/v) potassium ferricyanide in 10 ml test tubes. The mixtures were incubated for 20 min at 50 °C followed by addition of 2.5 ml of 10% trichloroacetic acid and then centrifugation at 6000 rpm for 10 min. The supernatant (2.5 ml) was mixed with 2.5 ml distilled water and 0.5 ml of ferric chloride (0.1% w/v), and the absorbance was measured at 700 nm (Hitachi, U-28000 Spectrophotometer, Tokyo, Japan). Increase in absorbance of the reaction mixture indicated the reducing power of the sample.

Sensory evaluation :

    Ostrich meat nuggets were prepared by deep frying in sunflower oil for 3 min to every side befor sensory evalution and coded nuggets samples were served at room temperature.  Colour, flavor, taste, juiceness, texture, overall acceptability of ostrich meat nuggets were subjectively evaluated using 10 panalist of Food Science and Technology Department, Faculty of Home Economic , Al-Azhar univ., Egypt. Hedonic ranking test where 9=extremely acceptable to 1=extremely rejected as described by Kramer and Twigg (1970).

    Statistical analysis :

The analyses were carried out in three replicates for all determinations. The means and standard deviation of way analysis of variance (ANOVA). A multiple comparison procedure of the treatment means was performed by Duncan's New Multiple Rang Test. Significance of the differences was defined as p < 0.05 (SPSS, 1997).

 

RESULTS AND DISCUSSION

 Proximate analysis of ostrich meat and broccoli powder (Bp) :

   The results of the chemical composition of ostrich meat and broccoli are presented in Table (2). The moisture, protein, ether extract and ash contents in the ostrich meat and broccoli were found to be (on wet weight basis) 72.97 and 87.41%, 24.83 and 3.08%, 0.74 and 0.56% and 1.38 and 1.26% respectively. Whereas, on dry weight basis, the values reached to 91.86 and 22.43%; 2.74 and 4.09%; 4.994 and 9.223% respectively. The results indicated that ostrich meat had low fat content (0.74%) and high protein content (24.83%) based on wet weight.These data were in the range reported in a previous study (Abou-Arab and Abu-Salem, 2010) which concluded the range of moisture, protein, lipid and ash in ostrich meat were 75%, 22.4%, 1.5% and 1.1%, respectively. Olga et al. (2009) revealed the chemical composition of broccoli floret and leaf flours i.e. 22.41g and 12.31g protein, 7.87g and 14.67g ash, 4.59 and 6.72g fat, 11.65 and 12.83g crude fiber and 65.13g and 66.48g of carbohydrates. Also, Alsuhaibani (2013) reported that protein, fat, fiber moisture ash and carbohydrate were 25.21, 3.25, 12.77, 7.31, 10.11 and 41.35% respectively in broccoli powder.

  

           Table (2): Proximate analysis of ostrich meat and broccoli powder

               * Carbohydrates were calculated by difference

                 Values are means of three replicates

 Antioxidant compounds in broccoli powder :

    Phenolic compounds are secondary metabolites that can neutralize or quench free radicals (Picchi et al. 2012). Data in Table (3) show that broccoli powder have a  considerable amount of total polyphenols 17.955 mg/g , these result confirmed possibility of using broocoli powder as antioxidant source in food processing. Flavonoids or bioflavonoids are unique low molecular weight ubiquitous polyphenolic compounds produced by plants during their metabolic activities as a secondary metabolites and responsible for major organoleptic characteristics and health benefits of plant derived foods (Kumar et al. 2013).  The value of total flavonoid reached to 56.56 mg/g as shown in Table (3) . In accordance, Borowski et al. (2008) reported that brocooli had high value of total phenol and flavonoids as the value were 87.38 and  19.96 mg/100g respectively .

 Glucosinolates constitute a major group of natural plant compounds in the family Brassicaceae. They are responsible for the hot and pungent flavor of crucifers and exhibit anticancer activity (Fahey et al. 2001).  From the obtained data (Table,3 ), it could be noticed that glucosinolates was represented about 9.15 mg/g as allyl isothiocyanate. The broccoli powder was found to possess good antioxidant activity, these results indicate capability to use broccoli powder as natural antioxidant in food processing. From the tabulated data (Table, 3), it could be noticed that antioxidant activity of broccoli powder which measured by DPPH , ABTS (both free nradical scavenging assays) and reducing power was 75.831%, 68.45% and 0.88 (absorbance), respectively. The reducing power of a compound is related to its electron-transfer ability; therefore, the reducing capacity of a compound may serve as a significant indicator of its potential antioxidant activity (Banerjee et al. 2012). Polyphenols are chemical compounds being secondary plant metabolites. They constitute the most abundant group of natural antioxidants, which can neutralize or quench free radicals (Rosicka-Kaczmarek, 2004, Picchi et al. 2012) Flavonoids and their derivatives are the largest group of plant polyphenols (Hounsome et al. 2009). They possess strong antioxidant activity due to their ability to scavenge reactive oxygen species and inhibit oxidative stress (Pourcel et al. 2007).

 

Table (3) : Total phenolic compounds, flavonoids, glucosinolates* and                    antioxidant activity of broccoli powder

               * Glucosinolates determined as allyl isothiocyanate

               ** Mean ± Standard deviation of three determinations

 

   Influence of broccoli powder (BP) on chemical composition of ostrich meat nuggets :

    The chemical composition of fresh ostrich meat nuggets as affected by addition of different levels of broccoli powder is presented in Table (4).

It could be noticed that the chemical composition of ostrich meat nuggets was affected by the addition of broccoli powder. The moisture content in ostrich meat nuggets samples was in the range of 63.73% to 66.62%. The moisture content was decreased with the increase in level of incorporation of broccoli powder in the product. This might be due to hygroscopic nature of the broccoli powder (Kumar et al. 2013). Similar findings were also reported by many researchers on addition of different powders and fat replacers (Kumar and Sharma, 2004 ; Mendiratta et al. 2013).  The protein and fat contents of the control (with or without synthetic antioxidant, BHA) were significantly (P < 0.05) higher than treatments. These results are in agreement with those reported by Kumar et al. (2013)  who found that protein and fat content of emu meat nuggets were decreased as broccoli powder in emu nuggets increased in their formula.

     The data in the same Table (4 ) shows that the ash and crude fiber of ostrich meat nuggets were significantly increased as the amounts of BP in its formula increased. This may be due to the property of broccoli powder, since it contains high crude fiber, ash and carbohydrate but low in protein comparing with ostrich meat.  These results are in the line with those reported by Kumar et al. (2013).

        As shown in Table (4), TBA value of ostrich meat nuggets was significantly (p < 0.05) affected by presence of broccoli powder in its formula. TBA value of control ostrich nuggets was 1.39 mg malonaldehyde / Kg sample significantly (p < 0.05) decreased to 0.89 in nuggets contains 8% broccoli powder. This may be due to presence of some polyphenolic compounds ,flavonoids and glucosinolates in broccoli powder which have an antioxidant activity to inhibit TBA formation. The highest TBA value of the control sample might be due to an interaction between the natural substances (for example, polyunsaturated fatty acids) and catalysts (for example, iron ion) from the meat tissue (Kim et al., 2000). So, mixing minced ostrich meat with various levels of broccoli powder caused a significant reduction of TBA values compared to control samples.

 

Table (4): Proximate chemical composition of ostrich meat nuggets as            affected by addition of broccoli powder

Mean ± Standard Deviation of three values

In a row, values have the same superscript letters are not significantly different by Dancen's Test at 5% level  

*  mg malonaldehyde / kg sample  

TBA value of raw ostrich meat = 0.98 mg malonaldehyde  /kg

 

 Influence of broccoli powder on physicochemical properties of ostrich meat nuggets :

       The pH, cooking loss, cooking yield and shrinkage of control, ostrich nuggets prepared with broccoli powder and BHA is presented in Table (5). pH value of fresh ostrich nuggets and BHA treatment was 6.28 (control), and 6.22 (control with BHA) significantly (p < 0.05) decreased to 6.21, 5.734, 5.451 and 5.33 in ostrich meat nuggets contained 2, 4, 6 and 8% broccoli powder respectively. The lower pH could be attributed to the relative increase in the concentration of organic acid in brocooli powder. Similar results were obtained by Banerjee et al. (2012) who found that higher amount of broccoli powder extract significantly decreased the pH value of goat meat nuggets. 

       Table (5) reveals that cooking loss of ostrich meat nuggets was gradually decreased contrary to cooking yield which was significantly (p <  0.05) increase by rose the percentage of added of broccoli powder. The lowest cooking loss (6.813%) was observed in ostrich nuggets contained 8% broccoli powder, in the meantime it had the significantly (p < 0.05) highest cooking yield (93.187%).

     Cooking yield was significantly (p < 0.05) higher for ostrich meat nuggets incorporated with broccoli powder than other treatments as well as control and BHA treatment. The increase in the cooking yield might be due to higher water retention properties of the fiber in broccoli powder.  These results are in agreement with those reported by Garcia et al. (2002) who reported an increase in cooking yield and moisture retention in dry fermented sausage upon incorporation of fruit fiber and cereals. Mehta et al. (2013) and Mendiratta et al. ( 2013) also reported an increase in cooking yield of meat products on incorporation of fruit and vegetables fibers.

      Table (5) shows that shrinkage (%) of ostrich meat nuggets significantly (p < 0.05) decreasd as the broccoli powder increased. For instance, shrinkage of control samples (with or without BHA) was 12.43 and 11.88%, respectively, which was markedely decreased to reash 5.48% for nuggets contained 8% broccoli powder. The depression in shrinkage of nuggets may be explained by the ability of broccoli powder to bind fat and to retain moisture. These results are in agreement with those reported by Bennion and Scheule (2004) who stated that Shrinkage of cooked meat was attributed to shortening of muscle fibers, coagulation of protein, loss of water and melting fat during frying.

 

 

 Table (5): Some physical properties of ostrich meat nuggets as affected by addition of broccoli powder at different levels

Mean ± Standard Deviation of three values

In a colum, values have the same superscript letters are not significantly different by Dancen's Test at 5% level

 Bp 2% = ostrich nuggets with 2% broccoli powder

Bp 4% = ostrich nuggets with 4% broccoli powder

Bp 6% = ostrich nuggets wih 6% broccoli powder

Bp 8% = ostrich nuggets with 8% broccoli powder

BHA  = ostrich nuggets with butylated hydroxyl anisol (150 mg/ kg)

 

 Antioxidant activity :

     The DPPH radical has been widely used to test the free radical scavenging ability of various natural products and has been accepted as a model compound for free radicals originating in lipids (Da Porto et al. 2000). The DPPH method used in this study to estimate antioxidant activity is based on the ability of antioxidants to reduce the DPPH free radical. DPPH free radical scavenging activity of ostrich meat nuggets incorporated with broccoli powder, control and BHA nuggets are shown in Table (6). The results showed that ostrich meat nuggets incorporated 8% broccoli powder had the highest DPPH, ABTS and reducing power comparing with another treatment or BHA nuggets. The percent radical scavenging activity of broccoli powder incorporated ostrich nuggets was increased significantly (p < 0.05) with the increase in the levels of incorporation, it did show proton donating ability and could serve as free radical inhibitors or scavengers that can be used as antioxidants. Banerjee et al. (2012) reported the DPPH radical scavenging activity of 2.25 mg and 3 mg broccoli powder was comparable to the activity of 50 and 100 ppm BHT, respectively. Kim et al. (2013) also reported the radical scavenging activity of broccoli powder.  The efficacies of antioxidants are often associated with their ability to scavenge stable free radicals of DPPH by donating electron to the unpaired valence electron at one atom of nitrogen bridge (Sreelatha and Padma, 2009; Krishnaraju et al. 2009). The DPPH free radical scavenging by antioxidants is due to their hydrogen donating ability; the more the number of hydroxyl groups, the higher the possibility of free radical scavenging ability (Chen and Ho, 1995). Broccoli powder and extract are rich source of various phenolic compounds (Kim et al. 2013) and thus can be incorporated into meat products as a source of natural antioxidants to prolong quality and stability.

 

 

 ABTS assay :

     All addition of broccoli powder showed effective scavenging activity against ABTS radical as shown in Table (6). Ostrich meat nuggets contained 8% broccoli powder produced the highest percentage inhibition comparing with another treatment or BHA nuggets. Also, ABTS scavenging activity showed increased significantly (p < 0.05) with the increasing levels of broccoli powder incorporation of ostrich meat nuggets. It has been observed that all the treated samples exhibited significantly (p < 0.05) higher ABTS scavenging activity than control (Table, 6 ). The high inhibitory percentage in ostrich nuggets contained broccoli powder could be attributed to the presence of flavonoids and polyphenolic compounds in broccoli powder. Even though DPPH and ABTS are both radical scavenging assays, percentage inhibition will vary due to different methods of preparation (Qwele, 2011). The DPPH radical is stable at formation whereas the ABTS assay allows formation of a radical which remains stable for several days due to the optimized pH (Cano et al. 1998), hence lower antioxidant scavenging activity.   

 

Ferric reducing antioxidant power:

    Table (6) shows the reducing power of ostrich nuggets with broccoli powder and BHA. The reducing powder of ostrich meat nuggets was influenced by addition of broccoli powder in its formula. Since reducing power of ostrich nuggets increased as the broccoli powder incorporate in its formula.

     For instance, reducing power of ostrich nuggets free from brocooli powder (control) was 0.43 significantly (p <  0.05) increased to 0.66, 0.73, 0.78, 0.89 for samples contained 2%, 4%, 6% and 8%, whereas was 0.63 in BHA (100 ppm) nuggets. Higher absorbance exhibited in ostrich nuggets contained 8% broccoli powder is due to the high polyphenolic content in broccoli powder. Additionally, it has been reported that the reducing power of bioactive compounds is directly related to its antioxidant activity (Iqbal and Bhanger, 2006). Amarowicz et al. (2004) observed a direct correlation between antioxidant activities and reducing power of certain plant extracts, which have been shown to exert antioxidant action by breaking the free radical chain through donation of hydrogen atom.

    The results indicate that broccoli powder provoke noticeable scavenging on free radicals and enhance the stability against primary oxidation. The presence of antioxidants in meat causes the reduction of Fe ³⁺/ ferric cyanide complex to the ferrous form (Fe ²⁺) (Chung et al. 2002). Broccoli had strong antioxidant activities due to their contents of total polyphenol, flavonoid and glucosinolates, which exhibited an ability to scavenge reactive oxygen species, metal chelators and inhibit oxidative stress (Pourcel et al. 2007; Charoensiri et al. 2009 ) . High contents of antioxidants may be found in fruits and vegetables as well as in their processed products. Their action is chiefly based on the neutralization of free radicals and on the prevention from oxidation processes (Sikora et al. 2008).

 

 

Table (6): Antioxidant potential of ostrich nuggets incorporated with different levels of broccoli powder

 

Mean ± Standard deviation of three values

In a column, values have the same superscript letters are not significantly different by Dancen's test at 5% level

Bp 2% = ostrich nuggets with 2% broccoli powder

Bp 4% = ostrich nuggets with 4% broccoli powder

Bp 6% = ostrich nuggets wih 6% broccoli powder

Bp 8% = ostrich nuggets with 8% broccoli powder

BHA  = ostrich nuggets with butylated hydroxyl anisole (150 mg / kg)

 

 Therefore, the importance of replacing synthetic antioxidants with natural ingredients from broccoli powder has greatly increased.

      Influence of added broccoli powder on organolyptic properties of             ostrich meat nuggets :  

      Sensory characteristics of ostrich meat nuggets as affected by adding different levels of broccoli powder and BHA (150 mg/kg) are presented in Table (7). No significant (p < 0.05) differences were observed in color, firmness, texture and juiciness between samples mixed with 2, 4, 6 and 8% broccoli powder to those mixed with BHA or control (without any addition) and the panelists did not detected differences between control ostrich meat nuggets and samples contained broccoli powder in previous sensory quality criteria.                                                                 These results are in agreement with those reported by Banerjee et al. (2012) who reported a non significant difference in the organoleptic characteristics of control and broccoli powder extract and BHT incorporated goat meat nuggets. From the obtained data (Table,7 ), it could be exhibited that there was significant (p < 0.05) difference between the control ostrich nuggets and those added with broccoli powder with regard to flavor, taste and overall acceptability. As seen from the results, panelists accepted the determined organoleptic properties of ostrich nuggets free or containing preserving agent or broccoli powder, all samples showed good overall acceptability; in all cases the values were higher than 8.0. So, the results of sensory evaluation suggest that the broccoli powder phenolic compounds can be successfully used as natural antioxidant without adversely affecting sensory characteristics of ostrich meat nuggets. Kumar et al. (2013) reported that nuggets with higher level of incorporation of broccoli powder showed a significant decreasing trend for color and appearance, flavor, tenderness juiciness and overall acceptability.

     The data in the same Table (7) shows that the significantly (p < 0.05) highest mean panelist's flavor value of ostrich meat nuggets (9.40) was detected for sample contained 2% broccoli powder. On the hand, the significantly (p < 0.05) lowest one (7.40) was observed for samples contained 8% broccoli powder (Table 7 ). This may be due to broccoli powder had a special flavor which affected on the flavor and taste of the final product. Mendiratta et al. (2013) reported  that vegetable incorporated mutton nuggets was successfully improved the functional and sensory quality.

 

Table (7): Sensory attributes (at Zero time) of ostrich meat nuggets as affected by addition of broccoli powder at different levels

 

Sample	Color (10)	Firmness (10)	Flavor (10)	Taste (10)	Texture (10)	Juiciness (10)	Overall acceptability (10)
Control	9.60 ±.5477 a	9.60 ±.8944 a	9.20 ±.4472 a	9.40 ±.5477 a	9.40 ±.8944 a	9.20±.8367a	9.50± .500a
Bp 2%	9.60 ±.8944 a	9.00±1.2247 a	9.40 ±.8944 a	8.80 ±.8367 ab	8.60 ± 1.1402a	8.80±.8367a	9.20±.8367a
Bp 4%	9.80 ±.4472 a	9.00 ±12247 a	8.40 ±1.1402 ab	8.40 ±.9844 abc	9.40 ±,8944 a	9.20±.8367a	9.00±.7071ab
Bp 6%	9.20 ±.8367 a	9.60 ±.5477 a	8.40 ±1.1402 ab	7.60 ±1.3416 bc	8.80 ± .8367a	8.40±.5477a	8.50±.500ab
Bp 8%	8.40 ±1.1402 a	9.20 ±1.0954 a	7.40 ±1.1402 b	7.20 ± 1.0954 c	8.40 ± .8944a	8.20± 1.0954a	8.00± 1.00b
BHA	9.20 ±1.7889 a	9.40 ±1.3416 a	8.60 ±.5477ab	8.60 ± 1.1402 abc	9.00± 1.00a	8.20± .8367a	8.90±.8944ab
F – value	1.163	0.321	2.900	3.200	0.948	1.526	2.426

 Mean ± Standard deviation of ten values

In a column, values have the same superscript letters are not significantly different at 5% level

Bp 2% = ostrich nuggets with 2% broccoli powder

Bp 4% = ostrich nuggets with 4% broccoli powder

Bp 6% = ostrich nuggets wih 6% broccoli powder

Bp 8% = ostrich nuggets with 8% broccoli powder

BHA  = ostrich nuggets with butylated hydroxyl anisole (150 mg / kg)

 

 Influence of refrigerated storage on chemical properties of ostrich meat      nuggets contained broccoli powder :

    As shown in Table (8), moisture content of ostrich nuggets was significantly (p < 0.05) decreased as storage period increased. These results are in agreement with those obtained by Rehab (2002) who reported that the decrease in moisture content in sasauge and beef meat during storage might due to the reduction in protein solubility and consequently decrease in water holding capacity. Also, the data indicate  that crude protein and crude lipid contents decreased in nugget samples after 15 day of storage at 4ºC.This reduction of protein and lipid may be due to hydrolysis of proteins and triglycerides by microbial enzymes. These results are in the line of Morsi (1988) who reported that the decrease of protein during cold storage could be attributed partially to the breakedown of proteins by protolytic enzymes which are not compeletly inactivated during cold storage as well as the loss of the nitrogenous compounds either as volatile substance caused by microbial effect by analogy. From the tabulated data, it could be noticed that ash content of ostrich nuggets incorporated broccoli powder was significantly (p < 0.05) decreased as the storage period increased.

 

Table (8) : Effect of refrigerated storage at 4ºC for 15 day on chemical properties of ostrich nuggets contained broccoli powder  

Mean ± Standard Deviation of three values

In a row, values have the same superscript letters are not significantly different by Dancen's Test at 5% level

 

     Influence of broccoli powder and BHA on TBA value of ostrich meat nuggets during refrigerated storage :

     Lipid oxidation is the major factor in reducing the quality and acceptability of meat and fat products (Morrissey et al. 1998). The effect of broccoli powder addition to ostrich meat nuggets on lipid oxidation during refrigerated period (15 day at 4ºC) was tabulated in Table (9). TBA value of all nuggets increased significantly with the advancement of storage period.   The TBA values of control sample increased significantly from 1.39 to 2.11   mg malonaldehyde/kg after 15 days of refrigerated storage.The increase in TBA of nuggets contained broccoli powder was lower than that of control sample. This reduction or delaying of lipid oxidation may due to the presence of the phenolic compounds of broccoli powder. Phenoilc compounds have free radical scavenger activity similar to the synthetic antioxidants and may also chelate metal ions, such as Fe⁺², result in the reduction of the formation rate of activated oxygen(Podsedek, 2007). However, these values were well below the acceptable limits (except control in the end of refrigerated period which recorded 2.11 mg malonaldehyde / Kg sample) of 1 – 2 mg malonaldehyde per kilogram meat (Witte et al. 1970).The difference was found to be non significant (p < 0.05) in between ostrich nuggets incorporated 8% broccoli powder and BHA (150 mg/kg) ostrich nuggets. Our results are in agreement with Banerjee et al.(2012) who reported that goat nuggets incorporated with broccoli powder had significant reduces in lipid peroxidation similar to 100 ppm BHT , thus improving the product quality and stability.

 

 

Table (9): Effect of broccoli powder and BHA on TBA value * of ostrich nuggets during refrigerated storage at 4ºC for 15 day

 

* mg malonaldehyde / kg sample

Mean ± Standard deviation of three values

In a column, values have the same superscript letters are not significantly different by Dancen's test at 5% level

Bp 2% = ostrich nuggets with 2% broccoli powder

Bp 4% = ostrich nuggets with 4% broccoli powder

Bp 6% = ostrich nuggets wih 6% broccoli powder

Bp 8% = ostrich nuggets with 8% broccoli powder

BHA  = ostrich nuggets with butylated hydroxyl anisole (150 mg / kg)

 

  Sensory attributes of ostrich nuggets contained broccoli powder as affected by refrigerated storage at 4ºC for 15 day :

      As shown in Table (10), the sensory attributes were significantly (p < 0.05)  affected during 15 day of refrigerated storage at 4ºC and all the sensory parameter viz color, firmness, flavor, taste, texture, juiciness and overall acceptability followed a descending trend (p < 0.05) with increase in storage periods. As the storage days progressed all the sensory properties followed a significant (p < 0.05) decreasing trend, however, in between treatments  and control sensory properties were comparable throughout the storage period. Table (10) show that ostrich nuggets made free from broccoli powder (control) had high color scores which significantly (p < 0.05) decrease after 15 day of refrigerated storage at 4ºC. This was propably due to the changes in the oxidation states of heam pigments or the interaction between amino amines and sugars in millared reaction (Hastings, 1989). The decrease in color score of ostrich nuggets with increase in storage period.

    Firmness scores followed  a decreasing trend throughout the period of refrigerated storage. A gradual  decline of flavor of ostrich nuggets contained broccoli powder might be due to the strong flavor of broccoli expected loss of volatile flavor component from condiments and spices during refrigerated storage at 4ºC of ostrich nuggets. The progressive decrease in flavor could be related to increase in thiobarbituric acid reacting substances value of meat products (Tarladgis et al. 1960).

     Texture scores followed a decreasing trend during the period of refrigerated storage. The lower textural scores might be due to loss of free water during storage. Similar  results  were presented by Thomas et al. (2006) in buffalo meat nuggets during refrigerated  storage. The overall acceptability scores of both  control and the treated nuggets with broccoli powder decrease significantly (p < 0.05) as the refrigerated storage progressed. This decrease might be reflective of the decline in scores of color, flavor, juiceness, taste and texture attributes. These results agree with these mentioned by Bloukas et al. (1997) who reported that overall acceptability  of meat products such as beef patties and frankfurter was decreased as the storage time extended.

 

Table (10): Changes in sensory properties of ostrich nuggets contained broccoli powder as affected by refrigerated storage at 4ºC for 15 day

 

 Mean ± Standard deviation of ten values

In a column, values have the same superscript letters are not significantly different at 5% level

Bp 2% = ostrich nuggets with 2% broccoli powder

Bp 4% = ostrich nuggets with 4% broccoli powder

Bp 6% = ostrich nuggets wih 6% broccoli powder

Bp 8% = ostrich nuggets with 8% broccoli powder

BHA  = ostrich nuggets with butylated hydroxyl anisole (150 mg / kg)

 

Conclusions :

     From the previous results, it could be concluded that broccoli powder is a good  source of natural antioxidant, so addition to meat products and foods may prevent against oxidative deterioration because of the high content of antioxidant compounds such as polyphenols and flavonoids. Thus, it can be used as natural antioxidants insteated of synthetic antioxidants which have negative effect on human health

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