| Summary: | 碩士 === 國立臺灣大學 === 畜產學研究所 === 91 === This study was focus on creation of a new dairy product “probiotics dairy tofu” by blending skim milk with glucono-δ-lactone (GDL) and inoculating selected probiotics. The purpose of this research was to evaluate the effects of the concentrations of GDL and skim milk powder, as well as addition of prebiotics and salt on the rheology and probiotics viabilities of probiotics dairy tofu and to attempt to apply modern optimization techniques to obtain optimal processing conditions and performance of the growth rate of selected probiotics by a process of response surface modeling. The end point was to develop a new dairy product and study the optimum models for its potential commercialization.
To carry out response surface modeling, Box Behnken Design was selected. The models were then formulated as an objective function in an optimization problem that was consequently optimized using genetic algorithms (GA) and sequential quadratic programming (SQP) approach to obtain the optimal processing conditions. The results showed the quadratic and cubic models appeared to have the most accurate response surface fit. GAs were able to identify the optimal combination for the manufacturing probiotics dairy tofu, while the SQP might stock in the local optimum.
The optimal producing conditions were suggested by the GA and SQP, and were verified by additional independent experiments. The resulted experimental values were no significant difference (p>0.05) from the predicted one. The optimal manufacturing conditions were obtained under conditions of maximum GDL, isomaltooligosacchride (IMO) and milk concentrations as well as minimum salt and peptides levels.
The viabilities of probiotics, hardness, organic acid levels, and concentrations of free amino acid in samples recommended by SQP were examined every week during a month storage. Results indicated that the hardness and amino acid level increased with time during a month storage, while the viabilities of probiotics were increased at the first week then decreased after. The sensory evaluation results showed that probiotics dairy tofu were no significant difference (p>0.05) from GDL tofu in texture and appearance.
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