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The manufacturing of ready-to-drink black tea was through a long process, up to 14-18 hours. There was an alternative way to produce RTD black tea directly on the farm to reduce time production and improve the quality of black tea using exogenous enzymes, i.e., tyrosinase and β-glucosidase. Tyrosinase was investigated for the ability to improve the color of tea extract by oxidize the phenolic content of green tea leaves to theaflavin and thearubigin, and β-glucosidase can enhance the volatile compounds by hydrolyze glycosidic bonds in tea leaves. Incubation of tea leaf extract with tyrosinase produces a high content of theaflavin and good color of tea extract but lowered the antioxidant activity. According to the TF/TR ratio values, tyrosinase treated tea leaf extract was in the best quality tea range. The use of β-glucosidase showed an increase in the proportion of good volatile compounds of linalool, linalool oxide, methyl salicylate, and β-damascenone.

This study is aimed at optimizing the Saffron essential oil (SEO) nanoparticles using the ionic gelation method. Response surface methodology (RSM) with Box-Behnken design (BBD) was applied to investigate the optimum conditions and the effects of three independent variables: LWCS concentration (0.1-0.3%), Arabic gum concentration (9.6-9.8%), and ratio (core: wall material) (1 : 5, 1 : 7.5, 1 : 10) on the responses of z-average, polydispersity index (PDI), and zeta potential. The results showed that the quadratic model developed from the RSM was statistically significant (p value < 0.05). The quadratic model can be used to describe well the relationship between the variables on the response observed. The lack of fit was nonsignificant (p value > 0.05) relative to pure error for all response variables, indicating that the model fitted well. The model equation obtained for the process through RSM was adequate. The LWCS concentration and Arabic gum concentration had a significant effect on z-average and PDI. The ratio (oil: Arabic gum/LWCS) has a significant effect on zeta potential. The optimum condition was the LWCS concentration of 0.1% and Arabic gum concentration of 9.6%, and the ratio (oil: Arabic gum/LWCS) 1 : 5 produced the optimum SEO nanoparticles with a z-average value of 16.24, PDI of 0.495, and zeta potential of 15.76. The verification values were close to the predictive value given by the Design Expert® 12 program with p value > 0.05 at the 95% confidence level. Therefore, the application of the RSM with Box-Behnken was suitable for optimizing the saffron oil nanoparticles with desirable responses.

Kabau, an unexplored crop, was analyzed to determine its nutrition and antinutrition components and in vitro protein digestibility (IVPD). Some conventional processes, such as steaming, frying, and boiling, were carried out to study their effect. The results indicated that all of the techniques reduced carbohydrate content. Frying significantly increased the fat content of Kabau and reduced other nutritional components. In general, all the methods significantly reduced phytic acid, tannin, and trypsin inhibitors, as much as 94.95–96.26%, 20–35%, and 89.22–92.88%, respectively. The reduction of antinutritional components resulted in higher IVPD on boiled and steamed Kabau, 69.47% and 61.48%, respectively.

Black tea aroma is one of the essential attributes in determining the quality of black tea. β-Glucosidases were investigated for their ability to enhance the aroma of black tea by hydrolyzing the glycoside compound. The addition of β-glucosidase was done by dissolving the enzyme on a sodium citrate buffer (pH 5.0), which was then sprayed on tea leaves during black tea processing. The β-glucosidase treatment significantly increases the volatile compound from glycoside precursors such as linalool, geraniol, and methyl salicylate. Moreover, the volatile compound from carotenoid and lipid precursors (nerolidol and β-cyclocitral) was also increased with β-glucosidase treatment.