Impact of selected coagulants and starters on primary proteolysis and amino acid release related to bitterness and structure of reduced-fat Cheddar cheese
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- Børsting, M.W., Qvist, K.B., Rasmussen, M. et al. Dairy Sci. & Technol. (2012) 92: 593. doi:10.1007/s13594-012-0080-7
Despite substantial research, it is still difficult to produce high quality reduced-fat Cheddar cheese. The objective of this study was to investigate how two coagulants, bovine chymosin (BC) and camel chymosin (CC) having different proteolytic activities and two starter cultures, an O-culture (O) and a thermophilic strain of Lactobacillus plus O-culture (OLb) having different abilities to release amino acids, contribute to the structure and flavour development in reduced-fat Cheddar cheese. Cheeses manufactured using the four combinations of coagulants and cultures were analysed during a 28-week ripening period for the composition of casein, peptides, free amino acids, rheological properties and for sensory properties at end of ripening. Cheeses with CC, showed less extensive primary proteolysis, lower levels of bitterness and higher stress at fracture, which correlates to a harder structure. Whereas cheeses with BC had a higher amount of peptides released by chymosin, e.g. the bitter peptide β-casein (f193–209) or by starter proteases from the chymosin-produced peptide αs1-CN (f1–23). BC cheeses were also judged to be softer by the sensory panel. Cheeses containing the OLb-culture had a higher amount of free amino acids and lower strain at fracture, which correlates to a shorter structure, and the peptide profiles of cheeses produced with BC and CC were rather similar after 28 weeks in contradiction to cheeses with O-culture. Replacing the traditional coagulant BC with CC reduced bitterness but increased hardness of the reduced-fat Cheddar cheese. Replacing O- with OLb-culture also reduced bitterness but resulted in a shorter structure. The results highlight tools which could be employed to alter primary proteolysis and amino acid release, respectively, for the optimisation of flavour and structure of reduced-fat cheese.
KeywordsReduced-fat Cheddar cheese Proteolysis Amino acid release Rheology Bitterness
虽然对低脂切达干酪进行了大量的研究,但是要生产高质量的低脂切达干酪任然面临着较大的困难。本文研究了具有不同蛋白水解活性的两种凝固剂牛凝乳酶(BC)和骆驼凝乳酶(CC),以及具有不同氨基酸释放能力的两种发酵剂O-发酵剂(O)和混合发酵剂嗜热乳杆菌+O-发酵剂(OLb)对低脂切达干酪结构和风味形成的作用。采用四种组合的凝固剂和发酵剂生产不同的低脂切达干酪,在28周的成熟期间,分析了干酪的酪蛋白、肽、游离氨基酸的组成及流变学特性,同时对成熟末期的干酪进行了感官评价。骆驼凝乳酶加工的低脂切达干酪,干酪蛋白酶解的程度较低,苦味物质含量也较低,但断裂应力较高,体现在较硬的干酪质构。然而用牛凝乳酶加工的低脂切达干酪,由凝乳酶释放的苦味肽β-酪蛋白(f193-209),或者由发酵剂蛋白酶产生的αS1-CN (f1-23) 肽含量都较高,干酪的质构较软。用OLb-发酵剂加工的低脂切达干酪中游离氨基酸含量较高,干酪的断裂应力也较高,这与干酪的脆性结构相一致;并且在28周成熟后期,牛凝乳酶和骆驼凝乳酶加工的低脂切达干酪的肽组成相似,但与O-发酵剂加工的干酪相反。采用骆驼凝乳酶替代传统的牛凝乳酶可以降低低脂切达干酪的苦味,但是增强了其硬度。用OLb-发酵剂替代O-发酵剂也能够降低干酪的苦味,但却导致了干酪质地变脆。因此,有望通过改变蛋白酶解和氨基酸的释放特性,从而改善低脂切达干酪的风味和结构。