The 7S and 11S globulins are major components of soybean protein. A novel freeze-thaw method for simplified fractionation of these proteins in soymilk has been developed. Raw soymilk was frozen at -30°C, and then thawed at 10°C for 24 h. The freeze-thawed soymilk was separated into two layers, and the weight ratio of the upper layer to the lower layer was 3:2. In SDS-PAGE analysis, the 11S/7S ratios were 0.14 and 1.7 in the upper and lower layers, respectively. Tofu curds were prepared using various ratios of the upper to lower layers. The breaking stress of the tofu curd increased with the increase of the lower layer. The curd made from the upper layer was soft and smooth, whereas that made from the lower layer was firm. A novel dessert-like product was made from the upper layer and a novel sausage-like product was made from the lower layer. These results show that rough separation of 7S and 11S globulins in raw soymilk can be achieved using a simple freeze-thaw treatment, thus facilitating the development of new food products.
Our studies on food science and technology for development of high quality food were reviewed. A series of papers deals with food aroma: 1) off-flavor generation in Satsuma mandarin juice during a pasteurization and improper storage, 2) aroma evaluation of coffee and sesame seed oil by multivariate analyses of GC data and sensory data, 3) analytical study on off-flavor of skim milk powder, 4) preparation of odor concentrate by solid phase extraction, 5) non-enzymatic formation of lactones in butter oil, 6) improving the palatability of salt-reduced food using soy sauce aroma, 7) characterization of odor terminology in Japanese, and 8) aroma sorption into plastic materials. A series of papers deals with food process engineering: 1) microbial and enzymatic inactivation under high pressure carbonation, 2) microbial inactivation by the high pressure hydrostatic treatment, and 3) rapid hygrothermal pasteurization of fruits and vegetables using saturated water vapor.
We developed a “nigori vinegar”, which possesses a rich and mild taste with a pleasant flavor, using only sake kasu. The nigori vinegar is made by fermentation of two kinds of enzyme-treated ginjo sake kasu with Acetobacter and lactic acid bacteria. Acetobacter is known to consume lactic acid, and this activity was suppressed by decreasing the stirring rate during aeration. As a result, the vinegar has a characteristic taste and flavor that is derived from the residual lactic acid, which is not contained in ordinary vinegar.
Foodborne diseases remain a serious global health problem. Campylobacter is recognized as the leading cause of bacterial foodborne diarrheal disease worldwide. In Japan, most cases of campylobacteriosis are associated with the consumption of contaminated raw or undercooked poultry meat or other foods cross-contaminated by these items during preparation. Campylobacter can be injured by food processing and preservation procedures. In particular, oxidative stress is known to induce cell injury; thus, many researchers have tried to develop an effective culture method to detect injured Campylobacter. As a result, Campylobacter enrichment media contains several reactive oxygen species (ROS) scavengers, such as pyruvic acid. Cultivation conditions, such as temperature and oxygen concentration, are also important for repairing cell injury. However, it remains difficult to recover injured Campylobacter cells from food and environmental samples. Further investigations of Campylobacter detection methods to recover injured cells and of the infection potential of injured cells are necessary to develop effective Campylobacter control strategies.
Bacteria in foods are killed or injured by sterilization with heat or sanitizers, or by treatments such as the addition of preservatives or shelf-life extenders. Microbiological testing by food companies typically involves cultivation, in which only healthy bacteria proliferate and injured bacteria do not grow. However, under certain conditions, the injured bacteria can recover, and the consequent sudden increase in the bacterial population results in the spoilage of foodstuffs. Therefore, it is crucial to determine the extent to which injured bacteria occur in the processing of foodstuffs. The present study utilizes a combination of nucleic acid binding agents (PMA) and real-time PCR to propose a method for monitoring viable, killed, and injured bacteria.