In 2014, the Ministry of Health, Labour and Welfare reported that flavor is the most valued aspect of food for consumers. Since flavor is a perception of the combined taste and smell of food, quantifying the taste and smell of food is useful in the rational design of desirable flavors. Taste and smell are also called chemical senses as they involve the detection of chemical components. Since 2000, progress in the identification of taste and olfactory receptors has made it possible to evaluate the taste and smell of food at a molecular level by cell-based receptor assays. Recently, molecular evaluation of taste and smell focusing on the chemosensory receptors has attracted attention. This review outlines the cell-based assay methods for these chemosensory receptors.

1, 5-Anhydro-D-fructose (1, 5-AF), which is produced from starch by the action of alpha-1, 4-glucan lyase, competitively inhibited Agaricus tyrosinase (L-tyrosine, L-dopa: oxygen oxidoreductase, EC 1.14.18.1) with a Ki value of ~20 mM. In silico modelling of the catalytic subunit of the enzyme docked with a 1, 5-AF molecule showed that only the keto form of the 1, 5-AF molecule could bind to the bottom of the active site of tyrosinase. The binding mode seemed to be very similar to that of tropolone, a strong, competitive inhibitor. 1, 5-AF also inhibited an enzyme partially purified from wheat flour and retarded the browning of commercial avocado paste. Thus, its colour protection activity, in conjunction with its bacteriostatic effect, appears applicable to food processing.

Hyaluronic acid (HA), a high-molecular-weight (MW) polysaccharide, has attracted considerable attention from the public because of its multifunctional health effects. Although the MW of HA is typically over 1 000 kDa, HA of less than 100 kDa (low-MW-HA) is currently manufactured and used in health foods to increase absorbability in humans. However, this has caused confusion in the definition of HA and has made accurate quantification difficult. Thus, a new so-called enzyme-HPLC method focusing on low-MW-HA was developed. Recombinant hyaluronidase was prepared and used to generate HA-disaccharides for quantitative accuracy optimization for low-MW-HA. Additionally, both saturated and unsaturated HA disaccharides were prepared as analytical standards. Further, a post-column-derivatization HPLC method was improved to simultaneously determine the two HA disaccharides following enzyme-hydrolysis of HA. A validation study was carried out by spiking a high-MW-HA standard material to a processed food. The resulting parameters were satisfactory: repeatability 0.8 %; intermediate precision 3.9 %; recovery 93.1 %. The lower quantification limit was inferred to be 0.01 g / 100 g. We also report new findings on the non-hyaluronic partial structures of an artificial low-MW-HA material.