Milk-Coagulating Extract Produced from Solanum aethiopicum Shum Fruits: Multivariate Techniques of Preparation, Thermal Stability and Effect on Milk Solids Recovery in Curd

This study investigated a novel procedure of Solanum aethiopicum Shum fruits extract (SASFE) preparation using multivariate experimental designs as factorial and Box–Behnken. The thermal stability of optimized extract as well as its influence on the milk solids in curd was determined. The results showed that extraction time, fruit maturity and pH did not affect significantly SASFE preparation, while the amount of fruits, extraction temperature and NaCl concentration of extractant had a significant effect (p < 0.05). The greatest coagulant index was obtained under the following conditions: 12.5% of fruits, 25°C of extraction temperature and 4% NaCl concentration of extractant. It was thermosensitive and exhibited optimum temperature at 50°C. There was no statistical difference between SASFE and calf rennet in terms of solids yield in curd, estimated yield and actual yield. On the basis of these results, SASFE can be used as a vegetable alternative to calf rennet.