Despite the high nutritional value of ripe red bell pepper (RBP) juice, RBP is typically considered a bitter vegetable. This excess bitterness affects the quality of RBP juice and results in rejection by consumers. We developed a manufacturing process to remove the bitter taste of RBP juice while retaining high nutrient levels. Compared to several resins, synthetic adsorbent resins had the most pronounced debittering effects, yielding the least bitter taste and green top note, while retaining a sweet taste and flavour. In particular, a styrene-divinylbenzene adsorbent resin having relatively large pores (pore radius ≥ 250 Å) removed more than 83 % of the bitterness of RBP juice, based on the quercetin-3-O-rhamnoside content. Moreover, vitamin B6 was retained at a high level, and the basic nutritional balance did not change after the treatment. The debittering effect was correlated with resin content, implying that quercetin-related flavonoids accounted for the bitter taste of RBP juice. Thus, resin adsorption is an efficient technique for the debittering and selective retention of high-value nutrition in RBP juice.

Although muscle atrophy can be caused by disuse and lifestyle-related syndromes, it may be possible to prevent this condition through dietary intervention. We hypothesized that a diet including red bell pepper juice (RBPJ) and soy protein isolate (SPI) would prevent muscle atrophy. Accordingly, an experimental diet containing RBPJ and/or SPI was administered for 18 d to normal C57BL/6J mice. The control group was administered a casein diet. Four days before the end of the test period, denervation-induced muscle atrophy and/or sham operation were performed. Anterior tibialis muscle samples were then obtained to assess muscle degradation and perform metabolome analysis. Under the denervation condition, the 20% SPI diet did not alter the mRNA expression levels of muscle atrophy marker genes compared with the 20% casein group. Although the diet comprising RBPJ and 20% casein did not prevent muscle atrophy compared with the control group, the diet containing RBPJ and 20% SPI did. Metabolome analysis revealed that a diet including RBPJ and SPI induced a greater than 1.5-fold change in the levels of 20 muscle atrophy-related metabolites. In particular, the level of S-adenosylmethionine, which concerned with energy metabolism and lifespan, showed a strong positive correlation with the muscle atrophy marker. These findings suggest that a diet including RBPJ and soy protein suppress gene expressions related with muscle atrophy. Further research in humans is needed to confirm whether a combination of RBPJ and SPI can indeed prevent muscle atrophy.