Optimization of moisture loss and fat uptake of goat meat during frying

Transcription

1 JOURNAL OF MEAT SCIENCE AND TECHNOLOGY Journal homepage: Optimization of moisture loss and fat uptake of goat meat during frying F.G. Sayyad 1*, P.P. Sutar 1, N.K. Agarwal 2 ORIGINAL ARTICLE 1 Assistant Professor, Department of Agricultural Process Engineering, CAET, AAU, Godhra, Gujarat, India. 1 Assistant Professor, Department of Agricultural Process and Food Engineering, PAE, AAU, Dahod, Gujarat, India. 2 Associate Professor, Department of Agricultural Process and Food Engineering, CAET, AAU, Godhra, Gujarat, India. *Corresponding Author: Sayyad F. G. faridsayyad786@yahoo.co.in Received: 03/09/2013 Revised: 20/09/2013 Accepted: 24/09/2013 Abstract Deep fat frying of chevon meat was carried out in refined sunflower oil and the effect of frying temperature and time on moisture and fat contents was investigated. Experiment were designed based on central composite, face centered designed with two independent variables namely, frying oil temperature ( C) and frying time (2-10 min) with two responses, moisture loss (%) and fat uptake (%). Quadratic model was fitted to the data and optimization was done using response surface methodology. The optimum conditions obtained were 182 C oil temperature and 10 min frying time resulting in moisture loss % and fat uptake %. Keywords: Deep fat frying, moisture losses, fat uptake Introduction The rapid expansion of fast food markets has increased the demand for meat, but increasing costs have resulted in trend towards increased consumption of convenient meat products. With rising income levels, consumption of processed foods and meat is increasing rapidly in developing countries. Consumer preference for goat meat is dictated by cultural and traditional background and socioeconomic status of the community. Virtually, no cultural or religious taboos restrict the eating of goat meat with the result that goat meat is readily available to societies, where eating of beef, pork and other meat types is prohibited (Casey, 1993). Deep fat frying is an important, ubiquitous and highly versatile process, which has been used since antiquity to cook a wide spectrum of products. Its unique contribution to sensory characteristics, together with the relatively low cost of large-scale frying, has made fried foods the staples of the ever growing late 20th century fast food industry (Saguy and Dana, 2003). Deep fat frying is the most common unit operation in food preparation to produce quality food for immediate consumption. It is process of cooking and drying through contact of hot oil and involves simultaneous heat and mass transfer. Factors that affect heat and mass transfer are the thermal and physiochemical properties of the food and the oil (Krokida et al., 2000). Deep-fat frying is a cooking process, in which food is immersed in edible oil at a temperature above the boiling point of water contained in that food; the oil temperature may range from 130 to 200 C, but is generally between 170 to 190 C. There are reports about the application of response surface methodology (RSM) for understanding the effect of different parameters on the rheological properties and optimization of processing parameters (Jayraj Rao and Patil, 2001; Diaz et al., 1996). First - order reaction kinetics mathematical models describing heat, moisture and fat contents were developed during deep fat frying of beef meatballs and validated against experimental data (Ateba and Mittal, 1994). Deep fat frying of breaded chicken pieces has been discussed from an engineering perspective using mathematical model to represent heat and mass transfer during frying (Mohan Rao and Delaney, 1995). Oil absorption and moisture loss phenomenon during deep frying of French fries were studied and effect of major process variable like frying oil temperature, size of potato chips

2 and concentration of hydrogenated oil in frying medium were examined and kinetic models developed (Krokida et al., 2000). Factors affecting oil uptake like frying temperature, duration, moisture content and product shape were reviewed by Saguy and Pinthus (1995). Mathematical model for heat transfer in meat patties during single side pan frying with and without turn over was developed using finite element method. Gupta et al. (2000) reported that the rate of both moisture loss and oil uptake were higher during the initial stages of frying followed by a decline. However, it is difficult to study and quantify individual and combined effects separately. Mass transfer during frying consists of moisture loss and oil absorption. Moisture loss during frying generally decreases exponentially with frying time. Costa and Oliveira (1999) suggested that predicting water loss is critical for modeling and controlling deep fat frying of potatoes. Heat and mass (moisture) transfer during deep-frying of frozen composite food was simultaneously modeled using the moving boundary concept. An explicit finite difference method was used to solve the proposed model. A model food composed of a chicken breast coated with batter at both ends was used to validate the predicted center temperature during frying at the specified oil temperatures (Chairath et al., 2003). One of the fundamental objectives of frying is to make food more acceptable. Fat is the natural palatable agent par excellence. During frying, the hot oil penetrating the product, replaces part of the water it contains, making the food considerably more palatable (Varela et al., 1988). Deep-fat frying has significant advantage over other cooking methods: the temperature within the product (aside from the crust region) is below 100 C; the frying time is short and there is insolubility of water-soluble vitamins. Therefore, less deterioration is expected to heat-sensitive vitamins, compared to baking or boiling (Saguy and Dana, 2003). In the present study, effect of frying time and oil temperature was studied on the moisture content and fat content of chevon meat followed by optimization of process conditions. Materials and Methods A male kid (chevon) of 10 months old Osmanabadi breed of goat was procured from local market of Rahuri, Maharashtra, India. It was slaughtered by halal method and dressed scientifically. Hot deboning was performed manually, lean meat and adipose tissues (fat) were kept in refrigerator at 4 ± 1 C. The chevon was cut in to 50 g pieces of 3 cm thickness. The pieces were thoroughly washed in clean water and smeared with salt, spices and cornstarch before frying. The medium in which frying takes place is usually a triglyceride oil used to fry chicken pieces in thermostatically controlled mini master fryer (M/s Continental Delhi, India) The bath had an effective volume of 6 litres, surface area of 920 cm 2 and temperature controllable up to 300 C. Oil was heated by 1800W electrical resistor. The resistor had an area of 0.046m 2 with a surface flux of 82.8Wm -2. Proper agitation of frying oil was ensured using a stirrer to maintain uniform temperature. The responses like moisture and fat contents were determined using AOAC (1990) methods. All the experiments were performed in triplicate and average values were taken for data analysis. The experimental design was done with 13 combinations of frying oil temperature ( C) and frying time (2-10 min) having 5 replicates at the center. The responses collected were, moisture loss (%) and fat uptake (%). During all experiments product to oil ratio was kept constant (1:10 w/w). Also, additional data on product temperature immediately after frying and sensory quality attribute was collected. The center points of the experimental design were defined as 180 C and 6 min. Experimental design is given in Table 1. Commercial software, Design Expert version (Stat-Ease, 2011) was used for statistical analysis and optimization. The RSM is combination of mathematical and statistical techniques that are useful for modeling and analysis of problems, in which response of interest is influenced by several variables. The main advantage of RSM is that it requires less number of experimental runs to provide sufficient information for statistically acceptable results. Response surface methodology (RSM) was used to reduce the number of experimental runs without affecting the accuracy 57

3 of results and determine interactive effect of variables on the responses (Cochran and Cox, 1957). Response surface methodology was used to estimate main effects on responses. Central composite design, face centered with two factors, two responses and five center points was used (Myers and Montgomery, 2002) to evaluate the experimental data as region of interest was encompassing region of operatability. Quadratic model used to describe the response variables is as follows. Y = ßo+ß 1 X 1 + ß 2 X 2 + ß 3 X ß 4 X ß 22 X 22 + ß 5 X 1 X 2 Where, Y is response (dependent variable); ßo, ß1, ß2, ß3 are regression (response) coefficients and X 1 and X 2, are code variables linearly related to time of frying (min.) and temperature of frying ( C). Sensory evaluation of the chevon meat samples by trained panelists using 9-point hedonic scales (Murray et al., 2001). Results and Discussion Evaluation of moisture and fat exchange: It can be observed from (Fig 1) that with increase in time of frying, moisture content decreased and fat content increased. It may be due to variable losses of moisture from the meat products (Keeton 1983; Kondaiah et al., 1992). The fat content increases with increasing frying time. Foods of plant origin absorb more fat than foods of animal origin. The moisture loss and fat uptake observed were in the range 42-51% and %, respectively. These results of statistical analysis were in accordance with the study performed by Moriea et al. (1995) with good correlation coefficients indicating the best fit for quadratic models (Table 2). The lack of fit F-values for quadratic models of moisture and fat contents were 0.62 and 0.70 respectively, which implied that the lack of fit was not significant in relation to pure error with probability values of 0.64 and 0.60 respectively. The quadratic models were obtained as follows: M = T θ-0.06tθ T θ 2 F = T+10.76θ-0.04Tθ-0.01T θ 2 Where, M is moisture content % wb, T is Oil temperature ( C), θ is Frying time (min) and F is fat content % wb. Table 1. Experimental design with real values Independent Variables Dependent Variables Serial No. Oil Temperature Frying Moisture % Fat % C Time (min)

4 Results of ANOVA showed that T, θ, Tθ, T 2, θ 2 were significant model terms (P<0.05) and the models for moisture and fat were highly significant (P<0.001). It was observed that selected quadratic model adequately represented the data for moisture and fat content (Table 2). Response surface for moisture content in relation to frying temperature and time has been shown in Fig.1, indicating an increase in moisture content with time and temperature. The moisture content graph shows that at higher temperature the moisture loss was fast as compared to lower temperatures. Standard error for moisture content varied from 0.49 to 1.17 and was least at the center of the experiments. Actual versus predicted data for moisture and fat content revealed that the model fitted best with residual ranging from to 1.40 and to 0.59, respectively. Response surface for fat uptake (Fig.2) indicated that as the frying time and temperature of oil increased the fat content was increased. Standard error for fat content revealed that the error near central region was low (0.31) while it increased towards end points. These graph clearly indicated that the frying time affected more moisture and fat contents as compared to temperature of frying. Evaluation of sensory characteristic: Sensory evaluation of chevon meat fried at 170, 180, 190 C for 2, 6 and 10 min along with optimized temperature and time (182 C, 10 min) are illustrate in Table 3. The characteristics were evaluated in terms of color, texture, aroma, chewiness, taste and overall acceptability by a panel of judges on a 9 point Hedonic scale. From the consolidated result it could be ascertained that the sample was not acceptable at 2 and 6 min of frying at all the three temperatures. Frying for 10 min yielded a better product at all the three temperatures. The organoleptically the product which was fried at 180 C for 10 min was subjected for sensory evaluation and found to be best. Raising the temperature of the fat higher than 185 C causes the fat to break down more rapidly due to an increased rate of oxidation and polymer formation in the fat. Also frying at 200 C or above, excess energy in the fat is converted into cross-links leading to case-hardening of food. This result in a brown surface forming on the food before the inside is completely cooked and immersing the food for a longer time to cook the inside properly may cause burning on the outside. Blumenthal ad Stier (1991) had reported that very high temperatures shorten the life of the fat. Table 2: Statistical analysis of data for moisture and fat contents Source Std Dev. R-Squared Adjusted R- Squared Predicted R- Squared PRESS Remarks Response Moisture (M): Linear FI Quadratic Suggested Cubic Aliased Response fat (F): Linear FI Quadratic Suggested Cubic Aliased 59

5 F a t M o is t u r e Sayyad et al. Optimization of moisture loss and fat uptake of goat meat during frying ign points above predicted value ign points below predicted value : oil temperature : frying time B: frying time A: oil temperature ert Software Fig 1: Effect of frying temperature and time on the moisture content of chevon oints above predicted value oints below predicted value 38 emperature ng time B: frying time A: oil temperature Fig 2: Effect of frying temperature and time on the fat content of chevon 60

6 B : f r y i n g t i m e D e s i r a b i l i t y Sayyad et al. Optimization of moisture loss and fat uptake of goat meat during frying Table 3: Sensory characteristics of fried chevon Parameter Colour Texture Aroma Chewiness Taste OAA Temp. Time (min) 2 2.5± ± ± ± ± ± C 6 4.0± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± C 6 4.8± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± C 6 5.1± ± ± ± ± ± ± ± ± ± ± ± C ± ± ± ± ± ±0.31 OAA-Overall Acceptability Design-Expert Software Desirability 1 0 X1 = A: oil temperature X2 = B: frying time B: frying time A: oil temperature Fig 3: Desirability of optimized conditions Design-Expert Software Overlay Plot Moisture Fat Design Points Overlay Plot Moisture: Fat: X Moisture: 45 X X1 = A: oil temperature X2 = B: frying time Fat: Moisture: Fat: A: oil temperature Fig 4: Overlay plot of optimized conditions 61

7 Optimization of the process conditions: Numerical optimization was carried out in relation to overall acceptability of the product. Standard deviation values for frying time and temperature were taken as 0.1 and 1, respectively. Moisture and fat content were kept at 29.7 and 31.4 % respectively, which could be obtained after 10 min 190 C. Propagation errors for moisture and fat contents were also kept minimum. Keeping these goals frying temperature and time were optimized. Optimization of the ingredient levels in sweet potato based pasta product using response surface methodology has been reported by Singh et al. (2004). It was found that. Thus optimized time and temperature for frying were 10 min and 182 C respectively with the moisture and fat content values and %, respectively. These results had desirability of The desirability plot in relation to factors has been shown in Fig.3. The contour plots of all the responses were then superimposed and optimum region appeared (Fig. 4). It shows combination of temperature, time, moisture content and fat. From which one can References AOAC Official methods of analysis 15 th edn. Association of Official Analytical Chemist. Washington DC. Ateba P and Mittal GS (1994). Dynamics of crust formation, kinetics of quality changes during frying of meatballs. Journal of Food Science, 59: , Blumenthal MM and Stier RF (1991). Optimization of deep fat frying operations. A review. Trends in Food Science and Technology, 2: Chairath T, Sakarindr B and Suvit T (2003). Heat and Mass Transfer during Deep-Fat Frying of Frozen Composite Foods with Thermal Protein Denaturation as Quality Index. Science Asia, 29: Cochran WG and Cox GM (1957). Experimental Designs. pp Costa RM and Oliveira FAR (1999). Modeling the kinetics of water loss during potato frying with a compartmental dynamic model. Journal of Food Engineering, 41, Diaz A, Totte A, Giroux F, Reynes M and Roult wack AL (1996). Deep fat frying of plantain (Musa paradisiaca L.). I. Characterization of control parameters. Lebensm Wiss Technology, 29: determine optimum process variables range (Oil temperature, frying time) for chevon meat frying. Conclusion RSM could be used as an important tool to optimize the frying conditions. The frying temperature and time were significantly affecting moisture loss and fat uptake of chevon meat with the effect of frying time being the most significant under the experimental conditions studied. The quadratic model is most suitable model to describe the moisture and fat content during frying of chevon meat. The moisture content decreased while the fat content increased with time and temperature of frying. The frying of meat for time 10 min at 182 C oil temperature results in to optimum product with moisture content 34.85% and fat content %. Acknowledgement The authors are thankful to Government of Gujarat for supporting above research work. Gupta P, Shivhare US and Bawa AS (2000). Studies on frying kinetics and quality of French fries. Drying Technology, 18: Jayraj Rao K and Patil GR (2001). A study on the effect of different hurdles on the rheological properties of fried paneer by response surface methodology. Journal of Food Science and Technology, 38: Krokida MK, Oreapolon V and Maroulis ZB (2000). Water loss and oil uptake as a function of frying time. Journal of Food Engineering, 44: Mohan Rao VN and Delaney RAM (1995). An engineering perspective on deep-fat frying of breaded chicken pieces. Food Technol, 49: Murray JM, Delahunty CM and Baxter IA (2001). Descriptive sensory analysis-past, present, future. Food Research International, 34: Myers RH and Montgomery DC (2002). Response surface methodology: Process and product optimization usig design experiments. 2 nd edn, John Wiley and Sons Inc, USA, p Saguy IS and Dana D (2003). Integrated approach to deep fat frying: engineering, nutrition, health and consumer aspects. Journal of Food Engineering, 56:

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