Abstract
Commercial caseinate and two gelatins from bovine and fish skin were hydrolyzed by alcalase, and used at 2 g/kg in skimmed bovine milk that was then fermented with a commercial direct vat set starter, to clarify different effects of these hydrolysates on acidification and textural attributes of set-style yogurt samples. Compared with the fermentation of the yogurt sample without hydrolysate addition, the two gelatin hydrolysates in the yogurt samples endowed lower titratable acidity but higher pH values and thus delayed yogurt fermentation, while the caseinate hydrolysate showed an effect opposite to the two gelatin hydrolysates. The two gelatin hydrolysates induced worse quality attributes for the resultant yogurt samples, including higher syneresis extent, smaller hysteresis loop areas, and lower values in these textural indices like hardness, adhesiveness, apparent viscosity, elastic and viscous moduli. However, the caseinate hydrolysate led to improved quality attributes. Moreover, bovine gelatin hydrolysate always had a greater negative effect than fish gelatin hydrolysate on yogurt acidification and texture. It is concluded that these gelatin hydrolysates could confer the yogurt with intended bio-activities of gelatin hydrolysates but negatively impact yogurt acidification and texture, while the caseinate hydrolysate might be helpful for yogurt processing by shortening fermentation time and improving yogurt texture.
Highlights
In the last couple of decades, the growing demand for body health has increased the production of healthy and functional foods
These yogurt samples showed some differences in their acid production during yogurt fermentation
Compared with the acid production in the control yogurt sample without hydrolysate addition, the addition of BGH and TGH in yogurt milk led to an inhibitory effect on acid production, while the addition of CH showed an opposite effect by enhancing acid production (Table 1)
Summary
In the last couple of decades, the growing demand for body health has increased the production of healthy and functional foods. Among these healthy and functional foods are fermented dairy products (especially yogurt) that offer several health benefits arisen from the fermentation of lactic acid bacteria. During the processing of yogurt products, food stabilizers can be used as yogurt additives for better quality attributes via improving consistency and micro-structure or decreasing syneresis of yogurt products [1,2]. In China, bovine gelatin is among these mostly applied additives in yogurt processing, because it demonstrates a powerful capacity to confer yogurt products (especially the set-style yogurt) with higher firmness and lower syneresis [3]. Other food additives or ingredients, such as prebiotics (e.g., inulin and β-glucan), probiotics (e.g., Bifidobacterium bifidum and Lactobacillus acidophilus), and several nutraceuticals (e.g., isoflavones and γ-aminobutyric acid), can be added to yogurt products for an attractive dimension, aiming to reduce disease risk [4], prevent rotavirus gastroenteritis and cardiovascular disease [4,5], decrease blood pressure and gastrointestinal disorders [6], and bring about hypoglycemic effect [4].
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