The effects of calcium concentration and cooling rate on the gelation of deacylated potassium gellan gum, a commercially available food additive, were investigated by circular dichroism spectroscopy, dynamic mechanical testing, compression testing, syneresis observation and scanning electron microscopy. Aqueous solutions of 0.15% gellan gum were adjusted to pH 3.8 in the presence of various concentrations of calcium after heating at 90°C. Gellan gum gels were then set under slow or rapid cooling rates from 80°C to 10°C. Gellan gum solutions with 6.5mM calcium showed higher saturated storage modulus values when cooled at the slow rate, as compared to rapid cooling from
40°C to 10°C. In agreement with these results, gellan gum gels set under slow cooling exhibited high breaking strength and fine structure. On the other hand, gellan gum solutions with 26mM calcium showed higher saturated storage modulus values when cooled at the rapid rate, as compared to slow cooling from 40°C to 10°C. Gellan gum gels set under rapid cooling exhibited high breaking strength and fine structure. Gellan gum texture was smooth at 6.5mM calcium, irrespective of cooling rate, but was rough at 26mM calcium. These results suggest that cooling rate has different effects on the gelation behavior and gel structure of gellan gum depending on calcium concentration.

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In this study, we aimed to search for peptides derived from casein with new anti-allergic action, and to examine the degranulation inhibitory effects associated with this anti-allergic action. Furthermore, amino acids making up the peptide with anti-allergic action were investigated for degranulation inhibitory effects, cytokine production and electron density. The peptides tested were low molecular weight HAQ, DMES, EQPI and KIKE, which are present in CE90GMM, a peptide mixture derived from casein. Using rat basophilic leukemia RBL-2H3 cells, we measured β-hexosaminidase levels released during degranulation in the antigen-antibody reaction in the presence of these peptides, and evaluated the anti-allergic effects. Cytokine production (TNF-α, IL-4) was evaluated by ELISA. Optimized structure and electron density of amino acids were analyzed using a three-dimensional of electrostatic potential. Significant inhibition of β-hexosaminidase release was seen with CE90GMM stimulation at 0.25 mg/mL. With the four types of peptide at levels ranging from 0.01 to 0.5 mg/mL, significant inhibition of β-hexosaminidase release was observed, but the effect varied with the dose. Our analysis also suggested that the peptides with anti-allergic action possess aromatic rings and neutral/hydrophobic amino acids in the side chain.

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The relationship between hardening phenomena during the moisture sorption processes and the water contents on baked wheat flour products was investigated for products with various ingredients and different baking methods ; conventional heating, and microwave combination heating. Higher values in maximum force (F_max) and total energy (E_t) were observed for higher levels of gelatinization products made from dough with higher water contents and in the case of baking with microwave combination heating. For more highly gelatinized starches with larger monolayer (W_m) and multilayer water contents (MC), marked hardening occurred at over R.H. 56 % and the hardening region expanded with humidity. In particular, MC at desorption was more closely related to hardening phenomena than MC at adsorption. The increase in anti-plasticization and the hardening region expansion of baked starch products during moisture sorption may be caused by the gelatinized starch gel forming with a high MC, which enhances microwave heating.

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The relationship between physical properties and water layers was investigated during the moisture sorption process in the following commercial confectionery products : wheat flour cookies ; biscuits ; crackers ; corn snacks ; potato chips ; wheat flour senbei (Japanese crackers), non-glutinous rice senbei, glutinous rice senbei and potato senbei. A brittle-fracture state was observed at about R.H. 7.6∼32 % in all samples, accompanied by hardening or softening at > ≈ R.H. 43 %. Wm (monolayer) and MC (multilayer) water contents were greater in products with higher levels of gelatinization, and hardened regions expanded upon high humidity. Wm and MC were more highly correlated to the physical properties during desorption than during adsorption, and brittle-fracture in all samples was associated with Wm, while hardening in most samples was associated with MC. Changes from a brittle-fracture state into a hardened state in starch products during moisture sorption processes might be caused by gelatinized starch gel, along with higher Wm and MC.

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The drying characteristics of fresh-cut apple pulp were investigated at drying temperatures ranging from 40 to 75°C. The hardening and browning effects of spraying with various solutions during hot air drying were evaluated between sprayed and non-sprayed sample surfaces. From the drying characteristic curves, it was determined that drying in both sprayed and non-sprayed samples was in the first falling rate period and the drying rate of the sprayed samples was greater than that of the non-sprayed samples. The results showed that spraying the sample surfaces during drying inhibited hardening and color change, and the total color difference (ΔE) during the drying process could be analyzed using an equation to describe the reaction kinetics. In addition, samples sprayed with a salt or ascorbic acid solution lost the least amount of polyphenol content. Therefore, periodically and appropriately spraying freshly cut apple pulp surfaces with solutions that act as antioxidants during the hot air drying process inhibits hardening and discoloration.

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The behavior of heat-resistant spore-forming bacteria (Bacillus cereus, B. subtilis, and B. coagulans) during storage in various coffee, black tea, and green tea drinks was investigated. Spores of each Bacillus species were inoculated into each drink. After heat pasteurization at the lowest condition under the Food Sanitation Act for soft drinks with ≥pH 4.6 (85°C, 30 min), viable bacterial counts under each optimum growth temperature were measured for two weeks. Viable counts of the three species of Bacillus inoculated into coffee, black tea, and green tea without milk decreased, whereas B. cereus and B. subtilis increased in coffee and black tea drink with milk. These results suggest that the commercial sterility of coffee, black tea, and green tea drinks without milk can be guaranteed with pasteurization of 85°C for 30 min, even if the Bacillus species is present.

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