Preparation and Analyses of Textural Quality and Flavor Substances of Goji Berry Yoghurt
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Abstract:
Goji berry puree and pure milk were chosen as the main raw materials, and the formula and fermentation conditions of goji berry yogurt were optimized by single factor tests and orthogonal experiments. Texture parameters of the yoghurts were determined by a physical property analyzer, while their composition and content of volatile flavor substances were analyzed by headspace-solid phase microextraction-gas chromatography-mass spectrometry. The results showed that the optimal formula of goji berry yogurt was as follows (on basis of the pure milk (mass fraction): goji berry puree, 5%; milk powder, 3%; sucrose, 10%; starter culture, 0.1%, fermentation temperature, 42 ℃; fermentation, 8 h. The sensory score for the optimized goji berry yogurt was 85.2, with the firmness as 28.32 g, consistency as 379.31 g•sec, cohesiveness as -18.35 g, viscosity index as -16.98 g•sec, and acidity as 100.20 °T. The correlation analysis showed that the firmness of the goji berry yoghurt was significantly and negatively correlated with the color and tissue status (r<0.001), and the consistency was positively correlated with the taste sensation (r<0.01), the color was significantly and positively correlated with the tissue status (r<0.001), the tissue status was significantly and positively correlated with the flavor (r<0.05), and the flavor was significantly and positively correlated with the taste sensation (r<0.001). The goji berry yogurt contained 32 of kinds of volatile flavor substances, with the content being 1 417.09 μg/kg. Compounds such as aldehydes in goji berry puree were the main flavor sources of the characteristic flavor of goji berry yogurt. The developed goji berry yoghurt is soft in color, and has a uniform texture, moderate consistency, delicate taste sensation, appropriate acidity and sweetness, with high nutrition and rich flavor.
