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In this study, we characterized protease activities of 23 Ficus carica cultivars. Extracts of fruit, branch, and leaf of Masui Dauphine, one of the most representative F. carica cultivars in Japan, exhibited gelatin-hydrolyzing activity, both in the absence and presence of a cysteine protease-specific inhibitor, E-64, suggesting that not only ficin (classified as cysteine protease) but also collagenase (classified as serine protease) were involved in the digestion of gelatin. In the hydrolysis of (7-methoxycoumarin-4-yl)acetyl-l-Lys-l-Pro-l-Leu-Gly-l-Leu-[N 3 -(2,4-dinitrophenyl)-l-2,3-diaminopropionyl]-l-Ala-l-Arg-NH 2 , all branch extracts of 23 F. carica cultivars exhibited the activity both in the absence and presence of cysteine protease-specific inhibitor E-64, indicating that they contain ficin and collagenase. During digestion of acid-solubilized type I collagen by the branch extract of Masui Dauphine at 40-55 °C, collagen was completely digested in the absence of E-64, while it was partially digested in the presence of the inhibitor, indicating that the manner of digestion differed between ficin and collagenase contained in the extract. These results suggest that F. carica is attractive for industrial use to digest collagen. PRACTICAL APPLICATION: The industrial use of F. carica might be enhanced by efficiently utilizing these proteases and/or selecting the appropriate F. carica cultivar. Collagen is one of the targets to which our results might be applied. It is widely accepted today that collagen and its digestion products could be useful as functional food. F. carica is a potential candidate for use in not only complete but also partial digestion of collagen., (© 2020 Institute of Food Technologists®.)

Freezing and thawing of oil-in-water (O/W) emulsion-type foods bring about oil-water separation and deterioration; hence, the effects of freezing and thawing conditions on the destabilization of O/W emulsions were examined. The freezing rate and thawing temperature hardly affected the stability of the O/W emulsion. O/W emulsions having different oil fractions were stored at temperatures ranging from -30 to -20 °C and then thawed. The stability after thawing depended on the storage temperature, irrespective of the oil fraction of the emulsion. A good correlation was found between the time at which the stability began to decrease and the time taken for the oil to crystalize. These results indicated that the dominant cause for the destabilization of the O/W emulsion during freezing and thawing is the crystallization of the oil phase and that the effects of the freezing and thawing rates on the stability are insignificant., (© 2017 Institute of Food Technologists®.)

We had earlier shown that the dispersion of wheat gluten in acetic acid solution conferred gliadin-like characteristics to the polymeric glutenins. To elucidate the molecular behavior of its polymeric glutenins, the characteristics of gluten powder prepared from dispersions with various types of acid were investigated in this study. Mixograph measurements showed that the acid-treated gluten powders, regardless of the type of acid, had dough properties markedly weakened in both resistance and elasticity properties, as though gliadin was supplemented. The polymeric glutenins extracted with 70% ethanol increased greatly in all acid-treated gluten powders. Size exclusion HPLC and SDS-PAGE indicated that the behavior of polymeric glutenins due to acid treatment was attributed to their subunit composition rich in high molecular weight glutenin subunit (HMW-GS) and not their molecular size. The gluten prepared with the addition of NaCl in acid dispersion had properties similar to those of the control gluten. The results suggest that ionic repulsion induced by acid dispersion made the polymeric glutenins rich in HMW-GS disaggregate, and therefore, act like gliadins., (© 2016 Institute of Food Technologists®)

Collagen is frequently digested using pepsin in industries to produce a triple helical collagen without the N- and C-terminal telopeptides. However, kinetic analysis of this reaction is difficult because several Lys residues in the N- and in the C-terminal telopeptides form covalent bonds, leading to multiple substrates species, and pepsin cleaves collagen at various sites in the N-terminal and in the C-terminal telopeptides, yielding different products. Here we performed kinetic analysis of the digestion of bovine type I collagen with porcine pepsin. The reaction could be monitored by SDS-PAGE by measuring the intensity of the protein bands corresponding to the variant β11 chain. We obtained kinetic parameters relative to the decrease in the variant β11 chain upon digestion. At pH 4.0, the Km and kcat values increased with increasing temperature (30 to 65 °C), although the kcat /Km values were stable. Additional cleavage at the helical region was detected at 45 to 65 °C. At 37 °C, the Km and kcat values increased with decreasing pH, and the kcat /Km values at pH 2.1 to 4.5 were stable and higher than those at pH 5.0 and 5.5. No additional cleavage was detected at the examined pH. Thus, the optimal pH and temperatures for selective digestion of collagen telopeptides with pepsin are 2.1 to 4.5 and 30 to 40 °C, respectively. These results suggest that the method might be useful for the kinetic analysis of the digestion of collagen telopeptides with pepsin., (© 2015 Institute of Food Technologists®)

Spaghetti dried at low (max. 50 °C), high (max. 70 °C), and very high (max. 85 °C) temperatures were characterized by their color, surface structure, rupture strength, texture analysis, and sauce retention capacity. The texture and sauce retention capacity were estimated for cooked spaghetti. The color of the spaghetti's methanol extracts, as evaluated through absorbance at 440 and 466 nm, did not depend on the drying temperature. A trend was observed in the surface texture of spaghetti, as estimated by atomic force microscopy and mercury intrusion porosimetry, where the surface was rougher when dried at higher temperatures than at low temperatures. Furthermore, the rupture strength was also higher for the spaghetti dried at higher temperatures. This result can be ascribed to the formation of stronger gluten networks, promoted by denaturation of gluten at the higher temperatures. However, the hardness of cooked spaghetti was not affected by the drying temperature, a result attributable to the action of water sorption to offset any differences in hardness among the spaghettis dried at the 3 different temperatures. The sauce retention capacity of cooked spaghetti was evaluated using a dextran solution as a simulated sauce, and by this method, the capacity of the spaghetti dried at a low temperature was shown to be significantly lower than that of the spaghetti dried at higher temperatures. This can be ascribed to the smoother surface of cooked spaghetti dried at the lower temperature and also to the leakage of amylose onto the surface during cooking., (© 2015 Institute of Food Technologists®)

Spray-dried gluten has unique properties and is commercially available in the food industry worldwide. In this study, we examined the viscoelastic properties of gluten powder prepared by dispersion in the presence of acetic acid or an ammonia solvent and then followed by lyophilization instead of a spray drying. Mixograph measurements showed that the acid- and ammonia-treated gluten powders had marked decreases in the time to peak dough resistance when compared with the control gluten powder. The integrals of the dough resistance and bandwidth for 3 min after peak dough resistance decreased in both treated gluten powders. Similar phenomena were observed when gliadin was supplemented to gluten powders. Basic and acidic conditions were applied to the acid- and ammonia-treated gluten powders, respectively, and the viscoelastic behaviors were found to depend on the pH in the gluten dispersion just before lyophilization. These behaviors suggest that gluten may assume a reversible change in viscoelasticity by a fluctuation in pH during gluten dispersion. SDS-PAGE showed that the extractable proteins substantially increased in some polymeric glutenins including the low molecular weight-glutenin subunit (LMW-GS) when the ammonia-treated gluten powder was extracted with 70% ethanol. In contrast, the extractable proteins markedly increased in many polymeric glutenins including the high molecular weight-glutenin subunit and/or the LMW-GS when the acid-treated gluten powder was extracted with 70% ethanol. It thus follows that the extractability of polymeric glutenin to ethanol increases similarly to gliadin when gluten is exposed to an acidic or a basic pH condition; therefore, glutenin adopts gliadin-like characteristics., (© 2015 Institute of Food Technologists®)

Tenobe somen (TS) noodles are traditional Japanese wheat-based noodles that are produced manually using a sophisticated method called tenobe (literally, "hand stretched"). In the tension test, both the tensile strength and extensibility of TS noodles were greater than those of machine-made (MS) noodles. In the biting test, the chewy texture of TS noodles was realized in the analysis of the force-deformation curves of each type of somen noodles. The creep test indicated a clear difference between the external and internal elasticity of TS noodles. The texture of TS noodles appeared to change dramatically during storage in the rainy season. In addition, firm and chewy textures of TS noodles stored for 20 mo were observed. Similar to the results from our previous study, TS noodles exhibited significantly higher dityrosine content than the flour used for their manufacture. However, the increase in the dityrosine content during the manufacturing process was not observed in the case of MS noodles. Although clear textural differences were observed between TS noodles stored for 0 and 20 mo, the dityrosine contents of TS noodles at each stage were not largely different., (© 2011 Institute of Food Technologists®)

Unlabelled: We investigated the effects of ice storage in a modified atmosphere on levels of glutathione (GSH) and its related enzyme activities, the metmyoglobin to total myoglobin ratio (metMb%), and the K value (a freshness index) of yellowtail fish muscle. GSH in ordinary muscle (fast skeletal muscle) as well as in dark muscle (slow skeletal muscle) stored in air decreased. GSH in those muscles was almost unchanged during storage when packaged with an oxygen absorber or with an oxygen absorber-CO(2) generator. Glutathione disulfide in each type of packaging remained at low concentrations during storage. The GSH peroxidase activities of ordinary muscle and of dark muscle after 7 d of storage in air were lower than when packaged with the oxygen absorber or with the oxygen absorber-CO(2) generator. The GSH reductase (GR) activities of ordinary muscle at the 4th and 7th day of storage when packaged with the oxygen absorber showed a tendency to be lower than when stored in air. The GR activity of dark muscle in each type of packaging method was unchanged during storage. The packaging method did not influence the K values of either the ordinary muscle or the dark muscle during storage. The metMb% of dark muscle when packaged with the oxygen absorber was lower than in the other types of packaging during storage. Therefore, packaging with the oxygen absorber is an effective method to prevent the loss of GSH in fish meat as well as to reduce the discoloration during storage., Practical Application: This study examined whether modified atmosphere packaging preserves the level of GSH, which is unstable to oxidative stress, in fish muscle. The use of an oxygen absorber for packaging can allow us to take in a sufficient amount of the bioactive compound from fish meat after storage as well as fresh fish., (© 2011 Institute of Food Technologists®)

Stone of Prunus mume (P. mume) is a by-product of pickled P. mume industry. Stones of native and pickled P. mume, mainly composed of holocellulose (83.8 +/- 1.8% and 65.1 +/- 0.3%, respectively) and acid-insoluble lignin (25.3 +/- 2.2% and 30.6 +/- 0.9%, respectively), were autohydrolyzed by microwave heating to extract polysaccharides and phenolic compounds. By heating at 200 to 230 degrees C, 48.0% to 60.8% of polysaccharide and 84.1% to 97.9% of phenolic compound were extracted in water along with partial degradation of hemicelluloses and lignin. The extracted liquors showed antioxidant activity against hydroxyl radical and DPPH radical originated from phenolic compounds. The pickled P. mume stone showed higher autohydrolyzability and microwave absorption capacity than the native stone due to absorbed salts and acids during pickling in fruit juice of P. mume with external addition of sodium chloride. Pickling process in salty and weak acidic juice seemed to be a kind of pretreatment for softening the stones prior to autohydrolysis induced by microwave heating.

We investigated the rheological properties of the Japanese wheat product tenobe somen noodles manufactured using a unique traditional process-"Te-nobe (hand-stretched)." In an extension test, the maximum resistance to extension (R(max)) and extensibility until rupture (Erup) of boiled somen noodles were measured on a Texture Analyzer in the tension test mode and compared with those of machine-made somen noodles. The R(max) and Erup values per unit cross-sectional area were significantly higher for boiled tenobe somen noodles than for machine-made somen noodles, clearly indicating the higher resistance to extension and extensibility of the former. A compression test performed using the Texture Analyzer in the biting-test mode revealed that although the maximum force of compression (F(max)) was lower for boiled tenobe somen noodles than for machine-made somen noodles, the former had more characteristic texture than the latter, which was shown by comparing the force-deformation curve of each somen noodle. Scanning electron microscopy revealed differences between dried tenobe and machine-made somen noodles, which may reflect their rheological differences. Lateral and sectional micrographs of tenobe somen noodles showed regular arrays of starch granules and gluten networks, and some air spaces. Tenobe somen noodles exhibited significantly higher dityrosine content than the flour used for their manufacture, indicating that tyrosine residues in gluten proteins cross-link during the manufacturing process; however, the dityrosine content in tenobe somen noodles were not higher than that in machine-made somen noodles.