A papain-catalyzed reaction permits covalent attachment of hydrophobic L-leucine n-butyl ester to hydrophilic gelatin to produce an enzymatically modified gelatin (EMG-4) with surfactancy [Agric. Biol. Chem., 45, 1621 (1981)]. EMG-4 and egg white (control) were dissolved in water and whipped by lower-speed mixing with an usual mixer and by higher-speed mixing with a homogenizer. In both cases of mixing, the overrun observed for the EMG-4 solution was lager than that observed for the egg white solution, and EMG-4 produced a finer and more stable foam structure than egg white. In the presence of added sugar, the EMG-4 foam was more viscous and elastic than the egg white foam. The jelly sample prepared with EMG-4 at a lower speed mixing showed the largest degree of overrun and, at the same time, the smallest value of hardness when measured with a texturometer at a low level of clearane.

View full abstract

A new method for minimizing heat loss in a vibro-fluidized bed freeze dryer was examined. A heater was set in a bed of granular materials. They were mixed smoothly by suitable conditions of vibration, and dried with uniform moisture content throughout the bed. Temperature at various positions in bed were almost the same. They were kept nearly constant at below 0°C during most of the drying period. The heater had no appreciable heat loss until the bed temperature became higher than the temperature of the wall of the drying chamber. The apparent thermal efficiency of the heater was evaluated as almost or more than 100%, because of the contribution of the heat generated by the vibration of the bed which was measured when the intensities of vibration were higher than the acceleration due to gravity. The heat transfer coefficient between the heater and the bed was about 500W/mm²·K at the initial point of the drying of the high moisture content materials. The value decreased with the drying process. After a period of drying, however, it showed a constant value of nearly 70W/mm²·K until the end of the drying process. The drying rates of this method were obtained up to about 6 kg-H₂O/mm²·h. These drying rates will be improved by the use of an appropriate proportion of capacity of the cold trap and the vacuum pump to the heat input.

View full abstract

The moist curdy leaf protein concentrate prepared by acid precipitation at pH 5.0 from white clover was extracted with ethanol at room temperature and the properties of ethanol-extracted leaf protein concentrate were compared with those of white leaf protein concentrate prepared by a conventional acid coagulation method. Ethanol was an effective solvent in removing lipids and pigments from crude leaf protein concentrate and ethanol-extracted leaf protein concentrate provided similar colour, proximate chemical composition and amino acid composition to those of white leaf protein concentrate. Yield of protein obtained by the ethanol extraction method was about 4 times higher than that in white leaf protein concentrate. However, solubility of protein was rather reduced by ethanol extraction. In addition, it was shown that drying method was important factor to obtain leaf protein concentrate favorable for an application to human food.

View full abstract

Effect of pH of water phase on creaming stability and electric conductivity of the kerosine-water (1:1) O/W emulsions stabilized with soybean phospholipids, that is, commercial soybean lecithin (CSL), ethanol-extracted lecithin from CSL (EL), phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI), were investigated. Higher stability waS generally obtained in the middle region of pH. The effect of the combinations of the phospholipids on the emulsion stability was cumulative. Electric conductivities of the emulsion phases of all samples decreased with aging time. The conductivity of the CSL emulsion was much higher than those of other phospholipid emulsions. The increasing order of the emulsion conductivities (PI>PE>PC) was parallel with that of the emulsion stability, and the conductivity of the PC emulsion showing worst stability was very low and decreased rapidly during aging. Very high conductivity was observed for the emulsions with two and three phospholipid mixtures and tevalue of the sample containing greater amount of PI was very high. These results suggest that the interfacial film structure and the charge strength of emulsion droplets may depend on the electrical charge of phospholipid resulting in the different stabilities of individual emulsions.

View full abstract

In order to examine the deterioration of the oil in fried Kamaboko (FK) of sardine, Sardinops melanostictus, which occurs by gamma-irradiation under air at 3 kGy and storage, the fatty acid content of the oil was determined by GLC. The chemical properties of the oil and the total bacterial count (TBC) of FK were measured. (1) Eighteen kinds of fatty acid content of the oil and the chemical properties showed almost no changes by irradiation. (2) During 21 days storage at 30°C, there were no changes and/or a slight decrease in saturated fatty acids and most of monoenoic acids in the oil in irradiated and unirradiated FK. Disappearance of C_16:1, _17:1, _20:3, _22:4ω6 and _22:5 acids which were low content of the oil in irradiated and unirradiated FK and a large decrease in C_22:6, _20:5, _18:3 and _18:2 acids were recognized. Not only showed a rapid increase in TBC in irradiated unirradiated FK as storage time increased, but a marked increase in POV and TBA value of the oil was also observed. (3) In 21 days storage of u irradiated FK at 10°C, deterioration of the oil was not large, but a rapid increase in TBC from the 7th on and changes in surface part of FK from the 10th on were seen. During 56 days storage of irradiated FK, deterioration of the oil and an increase in TBC were slight, and no changes in surface part of FK was observed. This fact indicated that combination of irradiation with low temperature storage was very effective for elongation of shelf-life of FK of sardine in almost the same as that of Alaska pollack reported in the previous paper.

View full abstract

Alanine and glutamate contents in plum fruits always increased during maturation and storage, and the increase was especially remarkable when deterioration of the fruit was progressing. Glutamate pyruvate transaminase (GPT), alanine dehydrogenase (ADH), aspartate-β-decarboxylase (ADC), glutamate dehydrogenase (GDH) and glutamate oxaloacetate transaminase (GOT) activities in 'Sordum' fruit were assayed to clarify the mechanism of alanine and glutamate accumulation. The fruit was stored at 20°C and 30°C. GOT and GPT activities in the fruit increased during ripening on the tree, and the increase was more notable in GOT activity. As GOT and GPT activities increased, rapid increase of glutamate and alanine occurred. The other enzyme activities did not change. During the storage at 20°C, GOT and GPT activities increased remarkably after 3 and 7 days, respectively. The increase of GOT activity was higher than that of GPT activity, and the former increased prior to the latter. Changes of glutamate and alanine contents nthe fruit coincided with those of GOT and GPT activities. Both of these enzyme activities and the contents of alanine and glutamate were less in the fruit stored at 30°C than those at 20°C. Pyruvate and glutamate, the substrates of GPT, and α-ketoglutarate and aspartate, the substrates of GOT, shoWed a tendency to increase in the fruit ripened on the tree. After harvest, however, pyruvate and α-ketoglutarate contents decreased at the beginning of storage at 20°C and 30°C. After that, those increased at 20°C, while at 30°C pyruvate content decreased and α-ketoglutarate content increased. Glutamate content increased during storage at both temperatures. Changes of aspartate content was not consistent during storage at 20°C, but remarkable increase was found at 30°C. From these results, it is assumed that the increase of glutamate and alanine in the fruit would be caused by the increase of GOT and GPT activities, respectively. The increase of GPT activity seems to be caused with accumulation of glutamate produced bGOT, which is activated prior to GPT.

View full abstract

A spoilage yeast isolated from sauce was identified as Saccharomyces bailii. The inhibition test of gas formation by the yeast under various concentrations of salt, sugar and acid which are major ingredients of the sauce was carried out. The relation between acid concentration (x%) and total osmotic pressure (y atm) of salt and sugar was investigated and the following formula: y=-55.2x+167.4 was obtained in order to prevent the gas formation. In the addition of ethyl alcohol to the sauce, the total osmotic pressure was elevated by that of ethyl alcohol. The formulas to calculate osmotic pressure (atm) from the concentration (c%) of the solute at 25°C were as follows: (759-8.4c) c/100-0.35c (w/v%) for sodium chloride, 71.4c/100-0.62c (w/v%) for sucrose, 135.6c/100-0.62c (w/v%) for glucose and 530c/100-c (v/v%) for ethyl alcohol.

View full abstract

The effects of CO₂ and N₂ gas and ethanol on the preservation and microflora of packed "Udon" (unboiled Japanese noodles) and "Chuka-men" (Chinese noodles) were studied. Total bacterial counts of unboiled "Udon" packed in CO₂ or N₂ gas and unboiled "Chuka-men" packed in N₂ gas were lower than those packed in air. Though the bacterial growth were suppressed by high pH (9.5-10.0) on unboiled "Chuka-men", total bacterial counts of noodles packed in CO₂ gas were higher than those packed in air because of lower pH caused by absorption of CO₂ gas. CO₂ and N₂ gas tend to inhibit the growth of Gram negatives and fungi. Ethanol tends to inhibit the growth of Gram negatives, and the growth of coli-forms were almost inhibited when the concentration of ethanol was 2% in noodles. Streptococcus was found to be the dominant flora during the preservation of unboiled noodles to which ethanol was added and packed with CO₂ or N₂ gas. Such tendency was remarkable in unboiled "Chuka-men".

View full abstract

Applicability of near infrared reflectance (NIR) method to determine moisture, protein and ash contents in buckwheat flour was confirmed. As the result of stepwise multiple-linear-regression analysis, the correlation coefficients between chemically analyzed values and estimated values by the regression were 0.997 on moisture with 6 wavelengths, 0.906 on protein with 6 wavelenghts and 0.952 on ash with 8 wavelengths. The standard errors of the estimation were 0.172, 0.301 and 0.125%, respectively.

View full abstract

The relationship between methods of drying cassava slices and biochemical changes during drying was investigated quantitatively. The study aimed at establishing a suitable method for cassava-flour making in tropical regions, and methods of evaluating cassava flour or chips for food quality. It was confirmed that the total amount of the coumarins in cassava flour varied according to the methods of preparation when prepared without heating. Further, the results indicated that peroxidase activity also depended on the changes in the methods. It is proposed that the analysis on the amount of coumarins or on the activity of peroxidase may be used as a tool to perform the above mentioned purposes on cas-sava-flour making. The phenols were also formed in cassava slices during drying, but appeared to be oxidized quickly. Thus, the amount of phenols was not correlated with the methods of making cassava flour.

View full abstract