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.
Supercritical CO2 with/without ethanol extraction of buttermilk was carried out at 50°C and various pressure and ethanol concentration conditions. Extracts were analyzed by TLC-FID and found to be mainly composed of triglycerides, obtained from both CO2 and CO2 with ethanol extractions, and polar lipids such phosphatidylcholine and sphingomyelin, obtained only from CO2 with ethanol extraction. A dynamic extraction model was applied to the obtained data and could describe extraction curves of solutes in the buttermilk. Solubility of triglycerides in supercritical CO2 obtained in this work was almost coincident with values in the literature. Although the solubilities of both phosphatidylcholine and sphingomyelin were not available in the literature because of the highly variable components, they could be estimated by applying the extraction model to the obtained extraction results.
Irradiation of ground beef and beef liver inoculated with Campylobacter jejuni was performed with gamma rays from a cobalt 60 source. Samples were packaged in gas barrier bags, sealed in air or under vacuum, and irradiated under refrigerated or frozen conditions. D10 values (dose required to inactivate 90% of a microbial population) ranged from 0.21 to 0.46kGy in ground beef and from 0.26 to 0.69kGy in beef liver. The D10 value for beef liver was higher than for ground beef under each irradiation condition, with the highest values being obtained under vacuum and frozen conditions.
The Great East Japan Earthquake seriously affected the town of Onagawa in Miyagi Prefecture, in the northern part of Japan. Local fishermen were forced to abandon their businesses because their fishing boats and equipment were completely destroyed or missing following the huge tsunami. Subsequently, they initiated planting of salt-resistant plants such as fig tree, hot pepper, and garlic to ensure their financial security. The fig trees were cultivated for the fruits; however, the harvest season of fig fruits was limited. Therefore, the production of fig leaf tea was attempted to expand their income base. The objectives of this study were to investigate the quality properties (components, functional properties, and taste) of fig leaf tea harvested in a tsunami salt-damaged area. The fig leaf tea contained abundant rutin and minerals, especially potassium and magnesium. In contrast, 1-deoxynojirimycin, caffeine, and catechins were not detected. Angiotensin I converting enzyme activity of fig leaf showed similar values to those of houttuynia tea, mulberry leaf tea, persimmon leaf tea, and rooibos tea. The taste properties measured by a taste sensor revealed weak astringent tastes. Additionally, fig leaf tea is a caffeine-free beverage, making it suitable for not only adults, but also those sensitive to the effects of caffeine such as children and pregnant women.
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.