Michiko Watanabe

A Mainstay of Functional Food Science in Japan—History, Present Status, and Future Outlook

The development of food science in the near future probably depends on the advance in functional food science, the concept of which was proposed first in Japan nearly 15 years ago. The new science has been internationally distributed and accepted as conceptually being beyond nutrition. In Japan, however, it traced a unique path of progress in the form of a product-driven rather than concept-driven science. Actually, a number of substances and products with potential for disease risk reduction rather than simply for health maintenance have been investigated for their body-modulating functions. Some of them have been applied in practice to the industrialization of functional foods in terms of “foods for specified health uses” legally defined by new legislation. A variety of sophisticated methods have been introduced as well, including the so-called “XYZ” evaluation system, database construction for assessment of the function, and even the DNA microarray technique. The Ministry of Agriculture, Forestry, and Fisheries (MAFF) and the Ministry of Health and Welfare (MHW) also commenced their scienctific as well as political activity, with its spread to industries which almost simultaneously began to vigorously investigate functional food products for enlargement of the food market. With all of this as a background, the Japan Liaison of the international Union of Food Science and Technology (IUFoST) hold a function food science symposium on behalf of related scientific bodies including the Japan Section of the International Life Science Institute (ILSI). This paper is an overview compiled from 12 presentations made in the symposium, with the aim of internationally publicizing the activity of functional food science in Japan.

4-Hydroxy-3-nitrophenylacetic and Sinapic Acids as Antibacterial Compounds from Mustard Seeds

A methanol extract from yellow mustard seeds had antibacterial activity against Escherichia coli, Salmonella enteritidis, and Staphylococcus aureus. Two compounds with such activity were isolated from the extract. By instrumental analysis, the compounds were identified as 4-hydroxy-3-nitrophenylacetic and sinapic acids. Examination of the structure-activity relationship showed that the hydroxyl and nitro groups of the first compound were involved in the activity against all three species. The two methoxyl groups and the hydroxyl group in sinapic acid were effective against E. coli and all of the substituents of the benzene ring were effective against S. enteritidis. The presence of the propenoic group of the second compound was effective against S. aureus.

Bacterial ice-nucleation activity and its application to freeze concentration of fresh foods for modification of their properties

Abstract Among various techniques for the removal of water from foods, freeze concentration is unique in that solutes in aqueous media are concentrated with the growth of ice crystals during freezing. In the presence of added ice-nucleation-active bacterial cells as ice nuclei, the bulk water in foods freezes at a subzero temperature near the melting point of ice. Since in general the bacterial ice-nucleation activity is so stable below 25°C, the seeding can be done at room temperature. For applications, we thus concentrated raw egg white and found the characteristic that the product formed a hard gel when heated and also gave a fine foam when whipped. The freeze-concentrated product from fresh milk was characterized by forming a gel when pressurized. A similar technique was applied to fresh lemon juice to obtain a concentrated product still retaining its original flavor. As another application, strawberry paste was separated into juice and pulp fractions, and the juice fraction alone was freeze-concentrated. The pulp fraction was then put back together with sugar, pectin and citric acid. We thus succeeded in making a non-heated jam which, compared to conventional jam, was almost equal in texture and superior in fresh flavor and colour.

An Active Compound against Allergen Absorption in Hypoallergenic Wheat Flour Produced by Enzymatic Modification

Hypoallergenic wheat flour produced by modification with cellulase and actinase showed inhibitory activity against ovalbumin permeation in an in vitro model by using the Caco-2 cell monolayer. The activity was found in the cellulase preparation used for producing the flour. An active compound was isolated by HPLC and identified as Trp-Ser-Asn-Ser-Gly-Asn-Phe-Val-Gly-Gly-Lys by 1H-NMR data and Edman degradation. The undecapeptide, some oligopeptides with the N-terminal sequences and Trp ethyl ester showed activity at 10-7 M, acetyl Trp being active at 10-2 M. These data suggest that the Trp residue without a free carboxyl group would be required for the inhibitory activity of ovalbumin absorption through the intestinal tract.

Polyphenols from Some Foodstuffs as Inhibitors of Ovalbumin Permeation through Caco-2 Cell Monolayers

Some spices showed high inhibitory activity against ovalbumin permeation through Caco-2 cell monolayers. Pimentol from allspice, rosmarinic acid and luteolin-7-O-β-glucuronide from thyme, quercetin-3-O-β-glucuronide from coriander and rutin from tarragon were identified as the active principles. A structure-activity relationship study among the active isolates and their related compounds indicated that the presence of a catechol structure played an important role in the inhibitory activity of each compound.

NMR analysis of a model pentapeptide, acetyl–Gln–Gln–Gln–Pro–Pro, as an epitope of wheat allergen.

NMR analysis of a model pentapeptide, acetyl (Ac)–Gln–Gln–Gln–Pro–Pro, as an epitope of a wheat allergen was performed. The problem of severe signal overlapping in the 1H NMR spectrum was overcome by elaborate two‐dimensional methods using 13C information. HMQC‐TOCSY allowed the assignments of the 1H and 13C NMR signals except the γ‐glutamylamide parts. E‐HSQC‐ROESY, which was constructed by modification of the E‐HSQC, could serve for discriminating ROEs of protons whose δH values were close to each other. Although the sensitivity of HSQC‐ROESY itself was low, selecting only CH carbons by adjusting the proper delay and flip angle of a pulse allowed a narrow F1 spectral width and hence the collection of numerous transients. As a result, the configurations of the amide bonds of the backbone were determined as all‐trans. ©1998 John Wiley & Sons, Ltd.

High-pressure Sterilization of Ice Nucleation-active Xanthomonas campestris and Its Application to Egg Processing

Xanthomonas campestris INXC-1 is able to freeze water at a subzero temperature higher than -5°C. High-pressure treatment at 300 MPa and 5°C for 5 min killed the cells without affecting their ice-nucleation activity. Egg white containing the pressurized cells began to freeze with a slight degree of supercooling. Ice crystals with a dendritic structure were formed when the egg white froze in the presence of the killed bacterial cells. The frozen egg white thawed more quickly than egg white frozen without the cells.

Soybean trypsin inhibitor and β-amylase stimulate macrophages

Mature soybean seeds were found to contain macrophage stimulation activity. The activity existed in a water-soluble fraction of soybean whey. Gel filtration, DEAE-cellulose column chromatography and high-performance liquid chromatography of the water-soluble fraction gave two active proteins. By N-terminal and total amino acid analyses, these were effectively stimulated by each of the two proteins to produce nitrite.

Screening, Isolation, and Identification of Food-originated Compounds Enhancing the Ice-nucleation Activity of Xanthomonas campestris

Some foods from plant sources, particularly of Moringeceae origin, contained compounds that enhanced bacterial ice-nucleation activity. A hot water extract from mustard seeds was so potent in its enhancing activity that the compounds responsible could be isolated from the seeds as yellow crystals. By instrumental analyses, this enhancer was identified as 4-hydroxy-3-nitrophenylacetic acid. The addition of a purified preparation of this compound at 0.1-1 ppm to the cultivation medium for Xanthomonas campestris was effective for enhancing its ice-nucleation activity.

The Plastein Reaction: Fundamentals and Applications

It has long been known that when a protein that has been hydrolysed by a protease is allowed to stand, it is sometimes transformed into a plastic gel-like product. Surprisingly, this phenomenon was first discovered a century ago.1 The product was then named ‘plastein’ and was thought to be formed through a reverse reaction catalysed by the protease. 1,2 It is now known that the substance ‘plastein’ does exist. Also, the term ‘plastein reaction’ is commonly used to refer to the protease-catalysed process involved in the formation of a plastein from a protein hydrolysate or an oligopeptide mixture. However, the definition of the plastein varies somewhat. Tauber3 defined plastein as a protein-like substance occurring in the water-insoluble fraction that results from the centrifugation of an entire plastein reaction product. Wieland4 defined a plastein as an acetone-insoluble fraction from a plastein reaction product. Determann & Kohler5 carried out a plastein reaction with a synthetic oligopeptide and obtained a series of polycondensates as the plastein reaction product. In recent studies conducted in order to develop the plastein reaction for various practical purposes, plastein has often been defined as the precipitate formed when an entire plastein-reaction product is treated with a typical protein denaturant such as trichloroacetic acid (TCA).6–10