Roxburgh rose is rich in nutrients such as polysaccharides and vitamin C as well as superoxide dismutase(SOD),and has the potential to reduce the risk and incidence of chronic diseases.In this study,Lactobacillus delbrueckii DMLD-H1(H1)and Streptococcus thermophilus DMST-H2(H2)were selected as the fermentation starters.By optimising the strain ratio,inoculation amount and the addition amount of Roxburgh rose juice,the optimal fermentation process for preparing Roxburgh rose yogurt was established.The physicochemical properties of the resulting Roxburgh rose yogurt were then compared with those of the yogurt produced using commercial strains.The results showed that the optimal fermentation conditions for Roxburgh rose yogurt were as follows:H1:H2=1:2;inoculation amount,1.0×107 CFU/mL;addition amount of Roxburgh rose juice,0.06 g/mL.The pH value of the Roxburgh rose yogurt obtained under such conditions was 4.47,with its acidity being 76.78 °T,and the water-holding capacity being 32.94%.From such a yoghurt,11 volatile substances were isolated,and the relative molecular masses of proteins were mainly in the range of 22～38 ku.The pH value of the yogurt decreased to 3.89 and the viable bacterial count was 1.1×108 CFU/mL after 4 weeks of post-acidification.After comparison with the commercial yogurt,it was found that the Roxburgh rose yogurt was able to inhibit yoghurt's post-acidification,improve the water-holding capacity,and increase the casein protein content of the yogurt;however,the Roxburgh rose may affect the original flavour substances in the yogurt.The study provides a theoretical basis for the development of a new type of Roxburgh rose yogurt and a reference for the development of new functional yogurts.
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