In this study, we optimized the coffee extraction conditions for instant coffee production in two stage percolators, which is the most common coffee extractor for instant coffee production. A central composite design was used to build mathematical model equations for response surface methodology (RSM). In these equations, the yield and overall acceptability of the coffee extracts were expressed as second-order functions of three factors, the feed water temperature, draw-off factor (DOF), and extraction time (cycle time). Based on the result of RSM, the optimum conditions were obtained with the use of desirability function approach (DFA) which find the best compromise area among multiple options. The optimum extraction conditions to maximize the yield and overall acceptability over 40% of yield were found with 163℃ of feed water temperature, 4.3 of DOF and 27 minutes of extraction time (cycle time). These results provide a basic data for the coffee extraction conditions for the competitive instant coffee in the industry.

Probiotic functional foods are known to have various functional effects such as intestinal regulation, modulation of immune system, reduction of allergies, and lowering of cholesterol. The purpose of this study was to select probiotic strain that is most suitable for freeze-dried coffee for the development of functional coffee products. The survival rate of probiotics, at drinking condition of coffee, at acid, at bile and after freeze-dried in coffee were measured on 1 strain isolated from commercial freeze-dried coffee, 8 strains used as fermented milk starter, 1 Bifidobacterium and 1 Bacillus coagulans. Bacillus coagulans showed the highest survival rate from 2.4×107 cfu/g to 2.0×107 cfu/g especially after freeze-drying. The results at drinking condition of coffee, at acid tolerance, at bile tolerance and at storage test showed significantly better survival rate of Bacillus coagulans than that of control (Lactobacillus casei). Especially, Bacillus coagulans showed 3.8-fold higher survival rate at acid tolerance (pH 1, 120 minutes) than control. Thus, the lactic acid-producing Bacillus coagulans is characterized as a probiotic strain suitable for functional coffee formulation and commercialization.

We have synthesized Eu3+-doped YVO4 phosphors by using a hydrothermal method and investigatedtheir luminescent properties. Aqueous solutions of Y2O3, V2O5, Eu2O3, and nitric acid with various pH valueswere used as the precursors. The crystallinity, surface condition, and emission characteristics were examinedusing XRD, FT-IR, and photo-excited spectrometer. Eu3+ incorporation followed by the efficient red emissionstrongly depends on the acidity of solution media. The emission intensity becomes stronger as the pH valuesincrease to 7 and then gradually decreases. This phenomenon might be related to the hydroxyl quenchingeffect, which is induced by surface bound OH- groups.