Food function can be broadly categorized into nutrition, palatability, and bioregulation. There has been rising interest in functional foods that are beneficial to bioregulation because of the increased onset of lifestyle-related diseases. Various food materials contain functional food components, and knowledge of their physiological functions has been accumulating. The intake of functional food components is recommended for maintaining and improving human health. However, many functional food components possess unpleasant tastes such as bitterness and astringency. Therefore, there is a concern that the palatability of functional food products will decrease as the content of functional food components within them increases. There is currently a dearth of established knowledge about the taste features of functional food components. Clarification of the taste features of functional food components is important for their application. On the other hand, some studies have shown that taste signals may induce specific biological responses, suggesting that the taste of functional food components might exert physiological effects. This review describes our achievements related to the taste features of functional food components.

Antioxidant activity, S-allylcysteine (SAC) and total polyphenol contents were measured in aged garlic extract, garlic extract, and garlic. The aged garlic extract had significantly higher 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, hydrophilic oxygen radical absorbance capacity (H-ORAC), and superoxide anion scavenging activity (SOSA) values than the garlic extract and garlic. SAC and total polyphenol contents showed a strong positive correlation (r > 0.90) with various antioxidant activities. These results suggest that aged garlic extract is a potential functional food with high antioxidant activity due to SAC and polyphenols.

Quercetin shows strong antioxidant activity, and it exerts prophylactic effects on arterial dysfunction through inhibitory actions on LDL cholesterol oxidation and platelet aggregation. Onion is the main dietary source of quercetin; however, the quercetin content in onion peel is 10 times higher than that in the bulb, and the peel is usually discarded before cooking. To use onion peel by-product, we prepared two onion peel extracts and examined their anti-platelet coagulation activity using rabbit and human platelets in vitro. Water was added to the onion peel, the mixture was heated at 110 °C for 90 min, and the whole peel extract was obtained. Next, the whole peel extract was subjected to centrifugation at 10 000 × g for 5 min, and the resultant precipitate was recovered. The ratios of quercetin and quercetin-4’-monoglucoside contents were 7:3 and 9.5:0.5 in the whole extract and precipitate, respectively. Using platelet activating factor, adenosine di-phosphate, and thrombin as stimulators of platelet aggregation, the whole peel extract and precipitate were assayed for anti-platelet coagulation. Both the peel extract and precipitate strongly inhibited the platelet coagulation stimulated by the three factors as well as quercetin. Further, we examined the activities of quercetin-4’-glucoside and quercetin-3-glucuronide; the inhibitory activity of quercetin-4’-glucoside was weaker than that of quercetin-3-glucuronide on human platelet aggregation. Following absorption of quercetin into human blood, it is metabolized to quercetin-3-glucuronide. The data obtained in this study indicated that onion peel may be a useful source of quercetin to prevent arterial dysfunction.

For the extraction process of the acid hydrolysis method, which is one of the main analytical methods for lipids, we developed a solid-phase extraction process using diatomaceous earth to replace the conventional liquid-liquid extraction process, and we evaluated its analytical performance.In the analysis of lipids and fatty acid compositions, we obtained equivalent results between the conventional process and the newly developed process.In addition, this new process reduced the experimental time (person-hours) when compared to the conventional process.From these results, we consider the solid-phase extraction process to be a suitable and useful substitute for the conventional process in the acid hydrolysis method.