Food emulsions are thermodynamically unstable systems due to destabilization processes such as flocculation, creaming and coalescence. Thus, the maintenance of kinetic stability is critically important to obtain high-quality commercial products. Our group has been studying the adsorption behavior and interaction at the interface of several components in oil-in-water emulsions, particularly, the two major components, i.e., proteins and low-molecular weight surfactants (emulsifiers) to understand the factors governing quality of food emulsions. In this review, I show the main results of our studies on food emulsions over the past 30 years. The topics are as follows: 1) the interaction of proteins and emulsifiers, particularly the displacement of proteins from the interface by emulsifiers; 2) Fat crystallization as a cause of partial coalescence of oil droplets; 3) Emulsion formation and stabilization by adsorption of fine particles; 4) Rapid evaluation of long-term stability of emulsions.
Amylose content was measured by the colorimetric determination and Concanavalin A (ConA) procedure. The difference between apparent amylose content measured by the colorimetric determination and amylose content measured by the Con A procedure should correspond with the amount of super long chains of amylopectin. Soft and less-sticky gel was obtained from high-amylose rice flour by adding 10 to 15 times the amount of water to rice flour and heating under continuous stirring. The texture of gel made from rice flour was measured according to claims of a consumer affairs agency. The hardness, cohesiveness, and adhesiveness of gel made from high-amylose rice flour with 10 or 15 times the amount of water were adaptable for a dysphagia diet. The ratio of gel adhesiveness to hardness could represent ease of swallowing. Significant correlations were observed between gel texture and amylose content. There was no significant change in gel texture after 3 days of storage under refrigeration.
The aim of this study was to determine the bioavailability of zinc in rats fed with zinc-enriched soybeans that were cultivated using a foliar spray containing zinc. Male Sprague Dawley rats were fed a basal diet (control), a zinc-deficient diet, or one of three test diets containing ordinary soybeans, zinc-enriched soybeans, and soybeans with zinc gluconate for 3 weeks. Body weight was significantly higher (p＜0.05) in rats fed zinc-enriched soybeans than in the control, ordinary soybean, and zinc-deficient diet groups. Apparent zinc absorption was also significantly higher (p＜0.05) in the zinc-enriched soybean group than in the control group (81.83±3.93 vs. 59.17±6.67%). Plasma superoxide dismutase and alkaline phosphatase activity in the zinc-enriched soybean group were significantly higher (p＜0.05) than in the zinc-deficient diet group. Moreover, bone strength was higher in the zinc-enriched soybean group compared with the zinc-deficient diet group (51.28±2.37 vs. 31.55±2.35N). These results suggest that the zinc in the zinc-enriched soybeans suppressed the inhibitory effect of phytic acid on zinc metabolism in rats.
Progressive freeze-concentration (PFC) was established as a much more flexible method regarding its operation, compared with the conventional equilibrium-suspension-crystallization method, which is limited to only continuous large-scale operation. PFC effectively concentrated water melon and melon juices, which are known to be difficult to concentrate because of their high heat-sensitivity and high viscosity. The concentrates were of high quality, retaining original flavor profiles, and are expected to be utilized as newly available foodstuffs.
Watermelon is thought to have originated in the Kalahari Desert and neighboring savanna zones in South Africa. The cultivation of watermelon was depicted in an Egyptian fresco 4000 years ago. Watermelon were introduced to Japan in the early Edo period. Watermelon called “Yamatosuika”, a natural cross between existing varieties and a new variety derived from America, received good publicity in the early Showa period. The Nara Prefecture Agricultural Experimental Station and Mr. Zentaro Hagihara, a private breeder, bred excellent varieties from the Taisho to the Showa period. Recently, using DNA markers based on genomic analysis technology, the breeding of watermelon and genetic purity inspection of F1 seeds has been performed more efficiently. Watermelon contains citrulline showing vasodilating action and lycopene having antioxidant ability. It is important to develop a method using the ingredients effectively.