• Korean Journal of Food Science and Technology
• /
• v.25 no.6
• /
• pp.747-752
• /
• 1993

A curd yogurt was prepared from milk added with skim milk powder or four kinds of starch such as rice starch, wheat starch, corn starch and potato starch. The effects of starch addition at 2%(w/v) level on acid production by lactic acid bacteria in milk was investigated. The effects of starch addition on quality of curd yogurt in terms of apparent viscosity, sensory property and volatile aroma compounds were also examined. Addition of starch markedly stimulated the acid production by lactic acid bacteria. Among four organisms tested, Lactobacillus jugurti produced the highest amount of acid. Apparent viscosity of curd yogurt added with starch was significantly higher than that of control. Curd yogurt fermented with L. jugurti showed pseudoplastic and thixotropic characteristics. Sensory property of curd yogurt added with corn starch or rice starch was evaluated as slightly better than reference sample, but that with potato starch was evaluated as the worst among all samples. Acetaldehyde, acetone, ethanol and butanol were detected by gas chromatographic analysis.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.31 no.1
• /
• pp.15-26
• /
• 2023

Methane production by anaerobic digestion occurs through interspecies electron transfer (DIET), a synthetic metabolism between acetic and methanate bacteria through hydrolysis and acid production steps. In this study, to improve methane yield, the effect of addition of magnetite (Fe₃O₄), a conductor promoting DIET on methane production in food wastewater was investigated, and the effect on methane yield was assessed by methane potential (B_u) and maximum methane production rate [R_m(t₀)] by the operation of batch type anaerobic reactor adding Fe₃O₄. The B_u and R_m(t₀) of food wastewater without Fe₃O₄ were 0.496 Nm³/kg-VSadded and 38.24 mL/day, respectively. The t0 which reached to R_m appeared at 21.06 days during the operation of the anaerobic reactor. The B_u of food wastewater with Fe₃O₄ was 0.502, 0.498, 0.512, 0.510, 0.518, 0.523, 0.524, 0.540, and 0.549 Nm³/kg-VSadded in the treatment of 5, 10, 15, 20, 25, 30, 40, 70, and 100mM-Fe₃O₄, respectively, and the B_u significantly increased to 36.95% with the addition of magnetite in the addition of 15mM-Fe₃O₄. And, the addition of Fe₃O₄ shortened the duration to reach R_m from 21.06 days to the maximum of 14.67 days by the addition of Fe₃O₄. Therefore, the methane yield and production rate of food wastewater significantly improved with the addition of Fe₃O₄.

• Microbiology and Biotechnology Letters
• /
• v.13 no.3
• /
• pp.191-198
• /
• 1985

Seven different strains of lactic bacteria and 13 combinations of these microorganisms were tested for their acid forming capacity on a vegetable milk made from lupinseed protein concentrate(LPC). L acidophilus, L casei, S. lactis, L. mesenteroides, mixed culture of L. acidophilus and S. thermophilus, and mixed culture of S. lactis and L. mesenteroides were selected and further tested for their growth pattern and acid forming property on lupinseed milk both untreated and partly hydrolized one with carbohydrate decomposing enzymes. The enzyme hydrolized lupinseed milk had 1.5 folds of total free sugar, 8.2 folds of fructose, 3 folds glucose, 2.3 folds maltose, compared to the untreated lupinseed milk. For the untreated lupinseed milk, L. mesenteroides was appeared to be most suitable microorganism having the maximum cell concentration of 1.0 $\times$ 10$^{9}$ $m\ell$ and the final pH 4.40 with the acidity 0.46％. For the enzyme treated lupinseed milk, mixed culture of L. acidophilus and S. thermophilus showed the best performance having 1.9$\times$10$^{9}$ $m\ell$ maximum cell number and the final pH and acidity were 3.69 and 1.13％, respectively. Lactic acid fermentation altered the physical property of lupinseed milk; by fermentation the viscosity generally increased with untreated lupinseed milk, but decreased with enzyme hydrolized one. The viscosity change and sedimentation rate of fermented milk varied with the type of lactic bacteria. The results of sensory evaluation indicated that S. lactis, L. casei, mixed culture of S. lactis and L. mesenteroides, and mixed culture of L. acidophilus and S. thermophilus, grown on enzyme hydrolized lupinseed milk, could produce acceptable lactic beverage.

• Korean Journal of Food Science and Technology
• /
• v.27 no.2
• /
• pp.156-163
• /
• 1995

The practical shelf-life of pasteurized Korean rice wine ‘Yakju’, aseptically packed in Tetra-pak, was determined. The test sample products were stored at $4^{\circ}C,\;20^{\circ}C,\;30^{\circ}C\;and\;35^{\circ}C$ for 19 weeks, and the quality assessment was made at two weeks interval. The quality parameters evaluated were pH, acidity, reducing sugar, absorbance at 370 nm, total and acid producing bacteria, yeast and mold, and sensory quality. No meaningful changes of pH and reducing sugar were noticed during the storage for 19 weeks at temperatures tested. The absorbance at 370 nm increased slightly during storage. The total numbers of microorganisms in the product decreased during storage and a drastical reduction of acid producing bacteria was observed after 6 weeks of storage. Both yeast and mold were not found in the pasteurized products. The sensory quality of stored rice-wine was evaluated by triangle test and scoring test. The panels could distinguish the product stored at $4^{\circ}C$ from other products stored at the higher temperatures for over 6 weeks. The overall acceptance of the product decreased gradually during storage, and the rate constants for the changes were $7.93{\times}10^{-3},\;at\;20^{\circ}C,\;9.69{\times}10^{-3}\;at\;30^{\circ}C\;and\;13.4{\times}10^{-3}\;at\;35^{\circ}C$, respectively. The activation energy estimated by Arrhenius equation was 24,795 kJ/kmol. The estimated shelf-life of Yakju pasteurized and aseptically packed was 24 months at $10^{\circ}C$, 16 months at $25^{\circ}C$ and 14 months at $25^{\circ}C$. The shelf-life of Yakju in Seoul was calculated to be 20 months, based on the monthly average temperature of the city.