• Applied Biological Chemistry
• /
• v.35 no.6
• /
• pp.490-494
• /
• 1992

The effect of heat treatments (boiling or microwave heating) on packaged Tofu was investigated by microbial and physicochemical changes during its storage in order to improve the shelf-life. The shelf-life of the packaged Tofu prepared by acetic acid was found better than that prepared by calcium chloride. As the spoilage of Tofu developed, titratable acidity, amino and ammonia nitrogen contents, and optical density of packaged Tofu suspension were increased. Heat treatment of fresh Tofu in package was effective in lowering the bacterial counts, and extending shelf-life, but there was no significant difference between heating methods. Packaged Tofu prepared from acetic acid and pretreated by heating for 3 minutes kept the shelf-life of 4 days at $30^{\circ}C$, but that without heat treatment spoiled at one day.

• Preventive Nutrition and Food Science
• /
• v.14 no.1
• /
• pp.71-75
• /
• 2009

The effects of Rhynchosia volubilis (yakong) incorporation (0%, 10%, 20%, and 30%, w/w of soybeans) on quality and shelf life of tofu were investigated. Moisture content of tofu increased slightly with the increase in the level of yakong incorporation from 10% to 30% and no apparent relationships between yakong incorporation and the yield were found. Turbidity of soybean whey tended to increase with increased level of yakong incorporation where the values of 20% and 30% samples were significantly different from those of control and 10% sample (p<0.05). The different levels of yakong incorporation were found to have significant influence (p<0.05) on all the color characteristics of tofu. Tofu texture varied with the level of yakong incorporation in consistent pattern; however, there was no significant difference (p>0.05) in most cases. Tofu incorporated with yakong ($10{\sim}30%$) had a shelf life of above at least 1 day longer than that of the control tofu.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.28 no.1
• /
• pp.161-166
• /
• 1999

CaCl2 and water soluble degraded chitosan mixtures were used as coagulants for extending the shelf life of tofu. Microbial counts, pH, and turbidity in tofu immersion solution were analyzed during the periods of storage at 4oC and physico chemical properties of tofu were determined by rheological properties, color and yield. There was no significant difference in moisture content and yield between tofu made with and without chitosan. Failure stress and stress relaxation values were reduced when chitosan was added to CaCl2, but there was no significant change among contents of chitosan added to tofu. The pH values were decreased at the beginning and then slowly increased after 14 days storage. The changes in turbidity were increased during storage, but the change in 2.0g degraded chitosan mixture with 7.0g CaCl2 coagulant(2.0:7.0 ratio) was lower than others and initial turbidity was lower as much as chitosan added to coagulant. These data showed that the water soluble degraded chitosan had a good anti microbial effect and increases the shelf life of tofu.

• Journal of the East Asian Society of Dietary Life
• /
• v.4 no.2
• /
• pp.69-74
• /
• 1994

In order to improve the shelf-life of Tofu, the elimination of contaminated bacteria by ozone treatment was examined. Tofu prepared from ozone treated-soybean was investigated for microbial, physicochemical and sensory changes during storage at 20$^{\circ}C$ and 30$^{\circ}C$. As a result of treatment in ozonic water by 2~4ppm/sec for 3 hours, 90~98% of the total bacteria in material soybean for Tofu was eliminated. At 20$^{\circ}C$, control Tofu prepared from ozone treated-soybean was found to be spoiled after 72 hous. Titratable acidity and sensory changes of Tofu was increased as spoilage of Tofu was progressed, but pH was decreased at the first day of storage, and after that it was increased. At 30$^{\circ}C$, there was no remarkable difference between Tofu of control and Tofu prepared from ozone treated-soybean.

• Applied Chemistry for Engineering
• /
• v.9 no.6
• /
• pp.889-893
• /
• 1998

In this research, mathematical models for predicting the shelf life of packaged tofu in a polyethylene container were developed. Transfer of oxygen in air through the package and then diffusion of oxygen into the filled water and the tofu with the simultaneous oxygen consumption by micoorganisms were studied. The results of simulation showed that the increase of microorganisms in the filled water was more than that in tofu. As a result, it turns out that the shelf life of packaged tofu was not determined by the number of microorganisms in the tofu, but by that in the filled water. Additionally, the effects of physical properties of packaging material and packaged materials, such as the oxygen permeability of packaging material, oxygen diffusion coefficient and the initial oxygen concentration in filled water, and the depth of the filled water, on the shelf life of packaged tofu, were observed.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.41 no.2
• /
• pp.77-83
• /
• 2008

This study investigated the quality of tofu prepared by treating soybean milk with deep seawater as a coagulant. The quality and shelf-life of the tofu prepared using the deep seawater coagulant were determined and compared to those using $CaSO_4$, surface seawater, and intermediate seawater coagulant. The tofu made with the deep seawater coagulant was firmest. In addition, the deep seawater tofu product had more, smaller particles in the microscopic view, compared to the tofu made from surface and intermediate seawater coagulants. The deep seawater tofu product had the lowest viable cell counts and turbidity. In addition, the deep seawater tofu product had a longer extended shelf-life. From these results, deep seawater appears to improve the texture, taste, and shelf-life of tofu when used as a coagulant.

• Korean Journal of Food Science and Technology
• /
• v.22 no.2
• /
• pp.116-122
• /
• 1990

In order to improve the shelf life of Tofu, the effect of calcium chloride or acetic acid as coagulants were investigated for microbial and physicochemical changes during the storage in different kinds of soaking solution. The soaking water of Tofu prepared from calcium chloride was found to be spoiled after 15-17 hours of storage at $30^{\circ}C$, by reaching the bacteria count to 10million per ml. The shelf life of the Tofu prepared from acetic acid was better than those prepared by calcium chloride. For the effect of soaking solution on storage life, soaking Tofu in 0.1% acetic acid was found to be more effective than soaking in other solutions of 3% NaCl or 0.1% K-sorbate. The optical density of soaking solution of Tofu increased in proportion to spoilage, and in case of soaked Tofu in 3% sodium chloride and 0.1% K-sorbate solution, it greatly increased. Titratable acidity, and amino nitrogen contents in soaking solution increased as spoilage of Tofu progressed, but pH decreased the early period, one or two days, of stored Tofu and then increased.

• Korean Journal of Food Science and Technology
• /
• v.41 no.3
• /
• pp.272-277
• /
• 2009

In this research, three dimensional mathematical models were developed to predict the shelf life of tofu packaged in a semi-rigid plastic container. A model combining oxygen transfer through the package and oxygen consumption within the package was considered. According to the results, the model simulations estimated that the number of microorganisms in the filled water was higher than that in the tofu, suggesting the shelf life of packaged tofu was not affected by the number of microorganisms in the tofu product, but rather by the number of organisms in the filled water. Additionally, the effects of the physical properties of the packaging material, such as oxygen permeability through the package, oxygen diffusion coefficient, the initial oxygen concentration in the filled water, and the depth of the filled water in the packaged tofu, were also observed.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.33 no.2
• /
• pp.412-419
• /
• 2004

To investigate the utilization of calcium lactates (CaL) as coagulants for tofu manufacture, the quality characteristics and shelf-life of tofu made by CaL-P (black snail powder) and CaL-A (black snail ash) were investigated and compared to calcium chloride (CC), magnesium chloride (MC), calcium sulfate (CS ) and standard calcium lactate (CaL-S). And also, total microbe and turbidity of the tofu were determined during storage at 1$0^{\circ}C$. Coagulation ability of CaL-A was the highest, and the ability of CaL-P was higher than that of CaL-S. Yield of CaL-A tofu was similar to those of CS and CC tofu, while the yield of CaL-P tofu was 50% compared to that of CC. L＊ value of CaL-P tofu was lower, but a＊ and b＊ values were higher than those of other tofus. The hardness of tofu showed in the order of CaL-S>CS>CC>CaL-P>MC>CaL-A, while the cohesiveness showed in the order of MC>CaL-S>CC>CS>CaL-P>CaL-A. Calcium contents were 57 mg% in MC tofu, 174 mg% in CS tofu, 116 mg% in CaL-S tofu, 95 mg% in CaL-A tofu and 172 mg% in CaL-P tofu. From the results of microscopic observations, the lower hardness showed the more soft and the smaller particle. The particle of CaL-A tofu was small and uniformity but the size of CaL-P and CC tofu showed coarse. Sensory quality of CaL-P and -A tofu were better than the other tofu evaluated by texture, springiness, flavor and overall taste. The shelf-life estimated by total microbe was 4∼6 days in CC, MC, CS, CaL-S and CaL-A tofu, but 8 days in CaL-P tofu at 1$0^{\circ}C$. From the above results, the CaL-P and -A may believe to use as coagulant for tofu manufacture due to its softened taste and enhanced shelf-life, and higher calcium content which has higher absorbability in human body.

• Korean Journal of Food Science and Technology
• /
• v.24 no.1
• /
• pp.92-96
• /
• 1992

Several coagulants was investigated for their effects on shelf-life of packed Tofu. The titratable acidity, amino nitrogen content in Tofu and the optical density of Tofu suspension were increased as the spoilage developed during storage. The number of microorganisms was increased to 13 million cells per gram after 1 day of storage at $30^{\circ}C$ in the Tofu prepared with $MgSO_{4}\;and\;CaCl_{2}$. But, the Tofu prepared from acetic acid was found to be more stable for storage. The quality of Tofu was maintained up to 12 days or 18 days at $30^{\circ}C\;or\;15^{\circ}C$, respectively. These results suggested that acetic acid was desirable as a coagulant of packed Tofu to extend its shelf life.