Enhancing the functionality of delactosed whey by enzymatic hydrolysis using Response Surface Methodology Approach (RSM)

Abstract

Delactosed whey (DLW), which has ~24% protein, is a by-product of lactose production and is mostly used as animal feed. DLW applications can be expanded to include food products, and its economic value improved by amplifying its protein functionality. Moderate enzymatic hydrolysis can significantly enhance protein functionality. It is, therefore, hypothesized that subjecting DLW to enzymatic proteolysis will lead to enhanced functionality. To amplify and improve the functionality of DLW via enzymatic hydrolysis, hydrolysis conditions need to be optimized. The infinite number of possible combinations of factors and their levels to be tested makes the task quite challenging. Using response surface methodology (RSM), the number of experimental units necessary to find the optimal point can be tailored depending on the time and resource constraints of the experimenter. The first objective was, therefore, to amplify the functional properties of the protein component of DLW by enzymatic hydrolysis using response surface methodology (RSM). The second objective was to monitor the functional properties and sensory quality of beef patties fortified with selected DLW hydrolysates as compared to those fortified with whey protein isolate (WPI) and whey protein concentrate 34% (WPC 34). In order to determine the optimal hydrolysis conditions, a Box-Behnken design with 4 independent variables at 3 levels was generated and implemented. The variables chosen, temperature (x1), enzyme-to-substrate (e/s) ratio (x2), time (x3) and pH (x4), are known to have the most significant influence on the degree of hydrolysis (DH) and protein functionality. The design had 27 experimental units that included 3 center points to assess the pure error. Each experimental unit was run in triplicate and the means of DH and measured functional properties were recorded as the y responses. The behavior of each response was explained by a quadratic equation. The effect of the independent variables on each response was evaluated and tridimensional response plots were generated. The conditions at which the responses were maximal/optimal were then determined. To validate the model, experimental data was obtained using the predicted optimized levels. iii In triplicate, ground beef patties were formulated using selected DLW hydrolysates, with optimized functionality, non-hydrolyzed DLW, WPC34 or WPI. A control sample was formulated without the addition of any whey protein ingredient. Cook loss due to losses in water and fat was assessed. Texture analysis of the cooked patties was done using a TA-XT2 texture analyzer. Sensory analysis was conducted to determine differences in various attributes among the different beef patties. Several response surface models were compared to determine the best fit for the RSM data collected. The point within the range of experimentation with the highest fitted value was determined. Using the model with the best fit (high R2 and P ≤ 0.05) for each response, prediction equations were generated and used to determine optimal hydrolysis conditions. Within the range tested, the emulsification capacity and activity of the DLW hydrolysates, produced under optimal conditions, were comparable to, if not greater, than that of WPI, which is known for its exceptional functionality attributes. The RSM approach provided an understanding of the effect of each hydrolysis parameter on the DH and on the assessed emulsification properties. Results highlighted that the extent of hydrolysis had a significant effect on the final functionality. While emulsification properties were enhanced significantly, hydrolysis of DLW was detrimental to the gelation property. Beef patties formulated with hydrolyzed DLW, with optimal emulsification properties, lost about half as much moisture as the control. The fat loss in the beef patties formulated with hydrolyzed DLW was about 5 times less than that of the control. The beef patty formulated with Alcalase hydrolyzed DLW had significantly (P < 0.05) higher compression force than the control. The functional performance of DLW hydrolysates in the formulated beef patties was comparable to that of WPI. While instrumental measurements indicated functional differences, the formulation with hydrolyzed DLW did not affect the sensory quality of the beef patties. Results of this work showed, for the first time, that the functionality of the protein component of DLW can be amplified upon limited and controlled hydrolysis. The tested DLW hydrolysates can be incorporated into meat products to amplify the functional properties without jeopardizing the overall sensory quality. Therefore, functionally iv enhanced DLW have a great potential to reduce processing cost by replacing WPI, while maintaining acceptable quality.