C: Food Chemistry JFS C: Food Chemistry Optimization of the Enzymatic Hydrolysis of Chicken Meat Using Response Surface Methodology L.E. KUROZAWA, K.J. PARK, AND M.D. HUBINGER ABSTRACT: The hydrolysis of chicken breast meat by the commercial protease Alcalase  2.4L was studied to evalu- ate the influence of temperature (43 to 77 ◦ C), enzyme:substrate ratio (0.8% to 4.2%), and pH (7.16 to 8.84) on the re- sponses of degree of hydrolysis and protein recovery. The enzymatic hydrolysis was optimized for maximum degree of hydrolysis and protein recovery using response surface methodology. The optimum conditions determined were the following: 52.5 ◦ C, 4.2% (w/w) enzyme:substrate ratio, and a pH value of 8.00. Under these conditions, a degree of hydrolysis of 31% and protein recovery of 91% were obtained. A characterization of the protein hydrolysate obtained using the optimized process conditions was carried out, evaluating the chemical composition, electrophoretic pro- file and amino acid composition. Keywords: degree of hydrolysis, hydrolysates characterization, protein recovery, screening design Introduction W hereas North and Central America and Europe have lost some share in the market, China and Brazil have become the new centers for chicken production in Asia and South America, re- spectively. In the last 5 y (2001 to 2005), Brazilian chicken meat pro- duction has increased by 38.3%, reaching almost 9 million tons in 2005 (FAO 2006). The breast of the chicken has a higher protein con- tent (22 g/100 g meat) and lower fat content (3 g/100 g meat) than other parts of the chicken such as the drumsticks (18 g protein and 5 g fat/100 g meat) and wings (18 g protein and 18 g fat/100 g meat) (TACO 2004). In addition, animal protein presents a perfect equi- librium of essential amino acids (or indispensable amino acids). An essential amino acid is an amino acid that cannot be synthesized by the organism and must therefore be supplied by the diet. According to Barbut (2002), novel processed poultry products (for example, poultry hot dogs) have been introduced onto the mar- ket in recent years, due to low raw material prices. In order to be competitive, the poultry industry must develop new products to satisfy emerging consumer demands and increase profitability. Thus the protein hydrolysis of chicken meat could be an alterna- tive solution to obtain value-added products. Protein hydrolysis can be accomplished using enzymes, acids, or alkali, but enzymatic hydrolysis is strongly preferred over chem- ical methods for the production of hydrolysates for food applica- tions. The proteolytic enzymes are used to dissolve or break down the meat muscle protein, resulting in 2 distinguishable fractions, the soluble and the insoluble fractions. The insoluble fraction can contain fat and other undesirable material and may be used in an- imal feeds. The soluble fraction contains the hydrolyzed protein with well-defined peptide profiles and a low fat content. During this MS 20070947 Submitted 12/19/2007, Accepted 3/6/2008. Authors Kurozawa and Hubinger are with Dept. of Food Engineering, Faculty of Food Engi- neering, State Univ. of Campinas, P.O. Box 6121, Campinas, SP, 13083-970, Brazil. Author Park is with Faculty of Agricultural Engineering, State Univ. of Campinas, P.O. Box 6011, 13084-971, Campinas, SP, Brazil. Direct in- quiries to author Hubinger (E-mail: mhub@fea.unicamp.br). process, amino acids are released, enhancing the flavor of the meat. The protein hydrolysates may be used as flavor enhancers, func- tional ingredients, or simply nutritional additives to foods of low protein quality. Protein hydrolysates are mainly applied in the nutritional man- agement of individuals who cannot digest whole/intact protein. Hydrolysates rich in low molecular weight peptides, especially di- and tri-peptides with as little as possible free amino acids, have been shown to have more dietary uses due to their high nutritional and therapeutic values (Bhaskar and others 2007). Extensively hy- drolyzed proteins also show reduced immunological reactivities, and can be used in formulas for hyperallergic infants (Mahmoud 1994). Furthermore, peptides, being easily absorbed, may be an op- timal nitrogen source in sports nutrition, and high biological value peptides are attractive as a general protein supplement in a wide variety of diets (Sliˇ zyt˙ e and others 2005). Enzymatic proteolysis and the dissolution of proteins from var- ious sources have been extensively studied, such as from red salmon, shrimp processing waste, catla, sheep visceral mass, grass carp, and mud snail (Sathivel and others 2005; Holanda and Netto 2006; Bhaskar and others 2007, 2008; Wasswa and others 2007; Xia and others 2007). However, little information is available on the en- zymatic hydrolysis of chicken meat. The most important variables in the enzymatic reaction have been reported to be the enzyme concentration and specificity of the enzyme, the reaction temperature and pH, and the nature of the protein substrate (Adler-Nissen 1985). It is important to know which of these factors are critical, since optimization of the process parameters for the enzymatic hydrolysis of meat is essential to de- velop an economical and optimal process. Response surface methodology has been employed in industrial investigations and other processes, due to its practical use in their optimization. This methodology presupposes the use of experi- mental design techniques to investigate and learn about the func- tional form of a process that involves one or more dependent vari- ables influenced by various factors or independent variables (Box and others 1978). Various authors have used this technique to study C  2008 Institute of Food Technologists Vol. 73, Nr. 5, 2008—JOURNAL OF FOOD SCIENCE C405 doi: 10.1111/j.1750-3841.2008.00765.x Further reproduction without permission is prohibited