Abstract
ABSTRACTBovine gelatin was cross-linked using horseradish peroxidase, glucose oxidase, and glucose, and then used in the preparation of set-style skimmed yoghurt. Both bovine and cross-linked gelatins were added into yoghurt milk at 2 g/kg, whilst the yoghurt milk composed of table sugar of 60 g/kg was fermented by a commercial direct vat set starter at 42°C for 5 h. Yoghurt samples stored at 4°C for 1 and 7 d were assessed for their compositions and quality indices. In comparison with that contained bovine gelatin, the yoghurt contained cross-linked gelatin had similar chemical indices in terms of protein, reducing sugars, and total solids contents, but exhibited lower syneresis, larger hysteresis loop area, higher apparent viscosity, elastic and viscous moduli, and improved microstructure. Cross-linked gelatin could delay yoghurt post-acidification slightly. Cross-linked gelatin was thus proved to be a potential stabilizer better than bovine gelatin to improve the quality of set-style skimmed yoghurt.
Highlights
Yoghurt is one of the most important fermented dairy products due to its good nutritious value and potential healthcare function
Yoghurt quality can be enhanced by addition of food stabilizers in yoghurt milk
Bovine gelatin or cross-linked gelatin was added to the skimmed milk at a level of 2 g/kg, whilst the table sugar was added at a level of 60 g/kg
Summary
Yoghurt is one of the most important fermented dairy products due to its good nutritious value and potential healthcare function. Some technological approaches have been used to improve yoghurt quality and especially to decrease the so-called syneresis (i.e. whey drainage); for example, by modifying the properties of milk proteins and/or adding food stabilizers such as gelatin, pectin, and various starch products. Cross-linking of milk proteins is one of the most important approaches to modify yoghurt quality. In the presence of glucose, horseradish peroxidase (HRP, EC 1.11.1.7) and glucose oxidase (EC 1.1.3.4) can induce an enzymatic cross-linking of milk proteins (Chang & Zhao, 2012) Using this enzymatic approach for whole and skimmed milk can confer the yoghurt samples with lower syneresis and finer texture (Chang, Kong, & Zhao, 2014; Han, Fu, & Zhao, 2015). CYTA – JOURNAL OF FOOD yoghurt quality can be efficiently improved by the addition of food stabilizers (Celik & Bakirci, 2003)
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