Effects of microbial transglutaminase (MTGase) on the texture of gel prepared from suketoudara surimi were investigated. The jelly strength and strain of the gel increased with an increase of MTGase. The texture improvement of surimi gel by MTGase was related to salt concentration, namely the jelly strength increased with an increase in salt concentration. The texture improvement by MTGase was observed even in low concentration of surimi diluted with water. The increase in jelly strength and strain of the gel was depressed by an addition of sucrose, and enhanced by an addition of potato starch. In the cases of the setting at below 30°C and at low concentrations of MTGase, the jelly strength increased in accordance with the prolongation of setting time. On the other hand, in the case of the setting at 40°C and 50°C, the jelly strength increased with setting time, and then reached constant. The content of ε-(γ-Glu) Lys linkage increased with an increase of MTGase. Especially, in the cases of suketoudara SA, its content increased rapidly by the setting at low temperature. Based on the results of SDS-PAGE, the band of myosin heavy chain (MHC) of SA surimi paled in the presence of MTGase above 1.5-3u/g protein, and that of C surimi faded at MTGase concentrations above 3-5u/g protein.

View full abstract

Effects of microbial transglutaminase (MTGase) on the texture of surimi gels prepared from eight kinds of fishes were investigated, The activity of Ca²⁺-ATPase at a low concentration (100mM) of KCI was related to freshness of frozen surimi responsible for texture formation of the gel. Suketoudara, itoyori and shiroguchi had high activities of endogenous transglutaminase. On the other hand, minamidara and pacific whiting had low activities of that. However, there was not an obvious relation between the activities of Ca²⁺-ATPase and the texture of surimi gels. It was observed that surimi from the fishes inhabited in cold areas of the sea provided the gel texture in the setting at low temperatures, and that surimi from the fishes inhabited in warm areas of the sea improved the gel texture by MTGase in the setting at high temperatures. The content of ε-(γ-Glu) Lys linkage increased in accordance with an addition of MTGase. Its content was high in the gels of suketoudara SA, minamidara, pacific whiting, hoki, and itoyori, and were low in the gels of hamo and shiroguchi. SDS-PAGE analysis showed that the band of myosin heavy chain (MHC) decreased with an increase of MTGase on the setting at 15°C, however, the band did not disappear even at 5u/g protein. On the setting at 40°C, the band of MHC disappeared with 0.5-1.5u of MTGase/g protein in every surimi gels.

View full abstract

"Jinhua Huotui" is a traditional fermented food produced in China. This study was aimed at identifying molds from "Jinhua Huotui" and evaluating their enzyme activities. All strains isolated were identified as being of the genus Penicillium (30 strains) and of the genus Aspergillus (25 strains). Of the genus Penicillium, P. aurantiogriseum, P. solitum, P. implicatum, P. viridicatum, P. fellutanum and other four kinds of molds were identified. Of the genes Aspergillus, A. versicolor, A. sydowii, A. candidus, Eurotium rubrum, E. amstelodami and other three kinds of molds were identified. As to enzyme activities, the genus Penicillium showed strong acidic protease activity, and the genus Aspergillus showed strong neutral and alkaline protease activities. Especially, A. ochaceus has strong protease activity as compared to the standard strain of A. oryzae. The genus Penicillium showed stronger lipase activities than the genus Aspergillus. Especially, P. fellutanum, P. canescens had very strong lipase activities. As to α-amylase and phoshatase activities, all molds isolated from "Jinhua Huotui" showed low activities. These results indicate that the genus Asperillus plays the main role for decomposition of protein, and the genus Penicillium does for decomposition of lipid in "Jinhua Huotui"

View full abstract

The foaming behavior of model solutions for coffee drinks with milk, in the presence of emulsifiers, was investigated by static surface tension, dynamic surface tension and bubble volume measurements. The chosen model solutions consisted of casein solution (0.87wt%) containing a defoaming agent (Sucrose laurate L 195: L, 200ppm) and/or a dispersion agent (Sucrose palmitate P 1670; P, 0-25ppm). The dynamic surface tension of model solutions decreased gradually with bubble formation time. Especially when a particle size of L was conditioned to 5 to 7μm and P was present in the solutions, the dynamic surface tension reduced remarkably down to 44mN/m within one second of bubble formation time. This behavior was an appropriate indication of the antifoaming action. Evaluation of antifoaming action by bubble volume measurement was closely correlated with that by the reduction in the dynamic surface tension of model solutions. In addition, applying static surface tension measurement to predict antifoaming action of food emulsifiers was also found to be unsuitable.

View full abstract

The quality of bread made by the frozen dough method is mainly evaluated by loaf volume and the roughness of bread crust. But the mechanism of occurrence of rough bread crust is still not elucidated. So effects of dough expansion rate before dough freezing on the rough bread crust were studied. When the dough expansion rate exceeded a reference rate before freezing, the rough bread crust always appeared in the product irrespective of temperature of a fermentor, the content of sugar or yeast in formula, fermentation activity of yeast, and storage period of frozen dough. Mortality of yeast in thawed dough was not related to the appearance of rough bread crust, because the yeast used can tolerate for freeze-thawing stress. Observation of bread crust and crumb by a video microscope revealed that the rough bread crust was color spots. The observed color spots of bread crust related to thickness, size, and tension of surface membrane and gas bubble membrane. Accordingly, the appearance of the rough bread crust so-called "nashihada" in the products obtained by the frozen dough method was not attributable to dead cells of freeze-tolerant yeast in frozen dough. These results suggested that the cause of dough rheological changes and rough bread crust was related to holding power of carbon dioxide gas of refrigerated dough and dough expansion rate before freezing.

View full abstract

Red rice is an old Japanese rice cultivar traditionally grown only for use in Shinto ceremonies. Recently, however, it has begun to be sold commercially. In this study, palatability evaluation and physicochemical properties of both red rice and Koshihikari were compared with those of standard Minenishiki. Taste, stickiness, hardness and synthetic evaluation scores in sensory tests showed definite preference for Koshihikari, while red rice was inferior the other two conventional cultivars. The protein and ash contents were at higher level in red rice which also showed greater hardness, less stickiness, and greater gumminess.

View full abstract

We are studying the deterioration of plant oil by thermogravimetry. We had reported that the behaviors of the TG curves of the deteriorated oil prepared at 100°C around weight decrease point was highly correlative to the peroxide value (POV). In this report, the autoxidated oil and the oil used at rice cracker production under most highest temperature were measured by thermogravimetry. In the case of rapeseed oil autoxidation, the TG curves at 190-290°C were recognized as behaving characteristically, namely those decreasing ratio has correlated with the POV and carbonyl value (COV), of which correlation coefficient was above 0.95. In the case of rice bran oil heating at high temperature (240-250°C), the temperature of 1% amount decreased point of TG curves has correlated with COV, acid value (AV) and color difference (ΔE), of which coefficients were above 0.91. From these results, it was suggested that the deterioration of plant oil will be evaluated by thermogravimetry.

View full abstract

Meat of spent laying hens is hard and its utilization value is low. Taking into consideration that the hardness of meat of spent laying hens is due to collagen which is a main component of connective tissue, we studied the relationship between meat toughness and the properties of collagen. The results are as follows: 1) Toughness of thigh, breast, gizzard, heart and liver of spent laying hens were harder than those of broiler. 2) Total collagen of thigh, breast, gizzard, heart, liver of spent laying hens were higher than those of broiler. 3) Heat-solubility (77°C, 63min) of thigh, breast, gizzard, heart, liver of spent laying hens were lower than those of broiler. 4) Pyridinoline content of type I collagen was higher than that of type III collagen in thigh of spent laying hens. From these results, toughness of meat of spent laying hen is presumed to be correlated with changes in properties of collagen. In addition, type III collagen is not so much responsible for meat toughness of spent laying hen.

View full abstract

On the quality of a bread made from a dough frozen for 20h before final proofing, the faster freezing (in dry ice, -80°C) was superior to the slower one (in the freezer, -20°C). We then tried to use a microbial ice nucleation-active (ina) protein which would accelerate the freezing of the dough moisture at a higher temperature. The bread made from the dough stored at-15°C with the ina protein added was the larger in loaf volume, the softer in texture and the less in the number of fish-eye like blisters than that without the ina protein, suggesting the potential utility of this protein as an ice nucleus for improvement of the frozen dough quality.

View full abstract

Twelve kinds of food proteins were hydrolyzed by Bacillus licheniformis alkaline proteases to form peptides of average chain length, 2.26-4.02. The hydrolyzates from shrimp, crab and sardine contained many di- and tri-residues whose angiotensin I converting enzyme (ACE) inhibitory activities were stronger than that of the hydrolyzates from soy bean, hair tail, oyster, beef, chicken, pork, chicken egg yolk, chicken egg white and casein. The IC50 was 0.072, 0.075 and 0.076mg protein/ml, respectively. Hydrophobic amino acid residues situated in the interior of protein molecules were exposed by fragmentation with proteases, and the peptides containing hydrophobic amino acid residues were found in aqueous solution. The peptide from casein showed the highest hydrophobicity and whose taste was the most bitter.

View full abstract

The near infrared (NIR) transmission method was assessed for determination of total sugar content, Brix value and acid content in strawberry juice. Calibration equations were obtained by multiple linear regression of measured values using standard methods and second derivative values of absorbance (dd²log (1/T)). For the spectra measured at a sample temperature of 24°C, bias-corrected standard errors of prediction (SEP) were 0.09% (w/v) for total sugar content, 0.09° Brix for Brix value and 0.033% (w/v) for acid content. Using the spectra which were measured at sample temperatures of 17, 24 and 30°C, SEP of total sugar content and Brix value were almost same as those in the above method, but SEP of acid content became a slightly bigger value (0.058% (w/v)). It was concluded that the NIR method could be employed to determine total sugar content and Brix value in strawberry juice with sufficient accuracy without control of the sample temperature. To determine total sugar content, dd²log (1/T) at 2268, 2326 and 1666nm were thought to be effective for calibration. The compositions of sugars in strawberry juices varied, but fructose and glucose levels were similar in all the samples. Moreover, although sucrose was changed into fructose and glucose by enzymatic action during the experiment, total sugar contents remained nearly constant and the ratio between fructose and glucose was also nearly constant. When this condition was kept, the values of dd²log (1/T) at 2268, 2326 and 1666nm were related to total sugar content. Furthermore, the value of dd²log (1/T) at 1666nm was not affected by acid content.

View full abstract

In the culture of thick bean sprouts of soybean and mung bean, dipping in solution phytohormone-treated culturing method were tested with the intention of producing good quality thick bean sprouts of short and thick hypocotyls, short roots and fewer root hairs on one hand, and, on the other hand, those with high moisture contents, yields as well as transparent-looking and glossy surface color tones concurrently. The effectiveness and applicability of the method were examined in terms of the growth, yield and moisture content, physical food property, as well as the color tone with the thick bean sprouts produced. Material beans were soaked in water for 5h at 25-27°C, after that they were sprayed with water of 27±2°C every 6h in germination beds kept at 27-30°C. After the germination treatments for 24h, they were immediately put on culturing beds kept at 27-30°C. Then they were sprayed with water (27±2°C) for 15min every 6h and aerated (aeration pressure; 1.2kg/cmcm², aeration rate; 1.5l/min) concurrently. Fourty-eight hours after the beans had been put on the beds, they were immersed in each 10.0ppm solution of phytohormone (Auxin: indole-3-acetic acid, Abscisic acid, Cytokinin: benzyl adenine, Gibberellin) for 6h, and then cultured for 5 days, i.c. 7 days in total. In the methods, the growths of both soybean and mung bean thick bean sprouts showed a similar trend in each dipping in solution phytohormone treatment. The comparison refered to the suitable values for marketing made on the 5th day after the cultures started showed that the auxin-as well as cytokinin-treated culturing methods controlled the hypocotyl elongation, root elongation and the number of developed root hairs effectively, whereas promoted the hypocotyl thickening and physical food properties. In addition, the color tone of the thick bean sprouts met the suitable value for marketing visually. The products, thus, indicated suitability for marketing as a whole in the aspect of quality, accordingly it became possible here to culture high-quality thick bean sprouts. Concerning the yield and moisture content, the estimating criteria from the economical aspect, the abscisic acid treatment was found to be a suitable method but the auxin and cytokinin treatments gave rise to reduced yields and moisture contents, and thus these treatments were found to be unsuitable methods; the gibberellin treatment showed intermediate behaviour of those described above with two groups of dipping in solution phytohormone. The cytokinin and auxin, dipping in solution phytohormone, treatments were effective and suitable for thick bean sprout cultures as the improving measures of the quality estimated in terms of the growth controls in hypocotyls and roots, as well as the intensification of physical food properties.

View full abstract

We investigated the production of brewing vinegar using agricultural products in Hokkaido area, in order to develop original brand products. We isolated acetic acid bacteria No. 1 from seed vinegar and investigated the conditions of acetic acid fermentation in order to utilize quince, apple, white asparagus and pumpkin produced in Hokkaido area. No. 1 strain did not grow on Hoyer-Frateur medium and did not produce dihydroxyacetone from glycerol. GC content of DNA of No. 1 strain was 53.8%. From the results, it was identified as Acetobacter pasteurianus. The acetic acid fermentation with apple juice and pumpkin pressed juice was only proceeded by addition of ethanol, while the addition of ethanol had no effect on acetic acid fermentation using asparagus and quince. The fermentation of asparagus was proceeded by addition of nitrogen source and organic acids after revising pH to 6.8. In quince juice fermentation, the addition of nitrogen source was effected after removing polyphenol by gelatin.

View full abstract

The substance inhibiting the growth of lactic acid bacteria in samac fruit, which is added to the sugarcane wine-"basi" in the Philippines, was isolated, and its structure was investigated. When the polyphenol components in the aqueous extract of samac fruit (AESF) were combined with gelatin and removed, the growth inhibition of lactic acid bacteria by AESF disappeared. Consequently, it was confirmed that the substance inhibiting the growth of lactic acid bacteria in AESF was the polyphenol component combined with gelatin. Furthermore, the three fractions separated from AESF by ultrafiltration were individually measured to determine the growth inhibition of lactic acid bacteria, and the fraction of M.W. below 1×10⁴, which contained 80% of the polyphenol components in AESF, was perceived to be the cause of the growth inhibition of lactic acid bacteria. Therefore, it was found that the substance inhibiting the growth of lactic acid bacteria was the low molecular weight polyphenol component. The substance inhibiting the growth of lactic acid bacteria in AESF was isolated using thin-layer chromatography, and it produced gallic acid, glucose and xylose by hydrolysis with HCl. Consequently, it was assumed that the substance inhibiting the growth of lactic acid bacteria in AESF was gallotannin.

View full abstract