Effects of natural catalysts, isothiocyanates and polysulfides, on Z-isomerization and decomposition of (all-E)carotenoids (lycopene, β-carotene, and astaxanthin) after heat treatment were investigated. When isothiocyanates were added to (all-E)-carotenoid solutions and heated, Z-isomerization and decomposition of carotenoids were enhanced and the degree differed depending on the isothiocyanate type. Interestingly, when polysulfides were applied in the same manner, in addition to promoting the Z-isomerization reaction, they markedly improved the thermal stability of carotenoids. Successively, we investigated the reaction characteristics of allyl isothiocyanate (AITC) and diallyl disulfide (DADS) using (all-E)-lycopene; that is, effects of the amount added, solvent used, and reaction temperature and time, as well as the combination use on Z-isomerization and decomposition of lycopene, were investigated. With increases in the amount added and reaction temperature and time, Z-isomerization of lycopene was promoted for both catalysts. The high-temperature treatment tests clearly showed that AITC induced thermal decomposition of lycopene, whereas DADS improved the lycopene stability. Moreover, the simultaneous use of AITC and DADS resulted in a synergetic effect on the Z-isomerization efficiency.

The aim of this study was to promote the Z-isomerization of lycopene in its extraction process from tomato pulp by adding foodstuffs containing Z-isomerization-accelerating compounds. The addition of onion, broccoli, mustard, makonbu (Saccharina japonica), or shiitake mushroom (Lentinus edodes) to the ethyl acetate extraction process significantly accelerated the Z-isomerization of lycopene. For example, when lycopene was extracted from tomato pulp at 70 °C without foodstuffs, the total Z-isomer ratio of lycopene in the extract was 38.4 ± 0.5%, whereas when onion, broccoli, mustard, makonbu, and shiitake mushroom were added to the process and the extraction was performed using the same procedure, the total Z-isomer ratios significantly increased to 53.6 ± 0.4, 47.9 ± 0.3, 48.2 ± 0.1, 41.5 ± 0.9, and 42.0 ± 1.2%, respectively. Since the above foodstuffs contain large amounts of carotenoid Z-isomerization-accelerating catalysts, i.e., polysulfides, isothiocyanates, or iodine, those components would promote Z-isomerization of lycopene in the extraction process. Since lycopene Z-isomers potentially have higher bioavailability and biological effects than the all-E-isomer, lycopene extraction with foodstuffs having a Z-isomerization-promoting effect in ethyl acetate should enhance the health benefits of tomato extracts.

such as tomato juice and puree 8, 9. However, lycopene Zisomers, such as the 5Z-and 9Z-isomers, are primarily found in animals and humans 8, 10, 11. A reason for the lycopene Z-isomer abundance in the body is thought to be the Z-isomerization during digestion and absorption 12 14. Re et al. reported that all-E-lycopene isomerized into the Zisomers in the human gastric juice and the 5Z-and 9Z-isomer ratios markedly increased 13. Recently, Huang and Hui found that the Z-isomerization site of all-E-lycopene was located in the small intestinal wall 14. Another possible reason for the high lycopene Z-isomer content in the body is that the Z-isomers are more bioavailable than the all-Eisomer. Several in vitro and in vivo comparative studies focusing on all-E-and Z-lycopene bioavailability have described greater lycopene Z-isomer bioavailability, and furthermore, human studies clearly showed that the ingestion of Z-isomer-rich diets resulted in higher Z-isomer ratio in the body compared to the ingestion of all-E-isomer-rich Abstract: Recent investigations have demonstrated that some food ingredients and vegetable oils, such as onion, garlic, and sesame oil, enhanced thermal Z-isomerization of (all-E)-lycopene in tomatoes. However, the synergistic effects of these ingredients and oils have not yet been investigated. This study aims at clarifying how the combined use of lycopene Z-isomerization-promoting food ingredients and vegetable oils impacts thermal Z-isomerization of (all-E)-lycopene in tomato puree. Apart from a few exceptions, when olive oil was used as a reaction medium, the combined use of garlic, cabbage, broccoli, shiitake mushroom, and makonbu improved the total Z-isomer ratio of lycopene after heating compared to the separate use of the tested ingredients. However, when onion was used together with the other ingredients, the Z-isomer ratio significantly decreased compared to its individual use. Moreover, when garlic, cabbage, broccoli, shiitake mushroom, and makonbu were used with sesame and mustard oils, that exhibit higher Z-isomerizationpromoting effect than that of olive oil, the lycopene Z-isomerization reaction was further enhanced. However, when onion was combined with these oils, the Z-isomer ratio decreased compared to that measured upon the combined use of onion with olive oil. Our results on these synergistic effects are not only important for the food and drink manufacturing industries but also for daily home cooking.

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.

Since lycopene Z-isomers exhibit greater bioavailability and biological activity than the naturally occurring all-Eisomer, efficient manufacturing methods for (Z)-lycopene-rich materials are urgently needed. Herein, a method was developed for Zisomerization of (all-E)-lycopene in tomato oleoresin using heat treatment and a natural catalyst, viz. allyl isothiocyanate (AITC). For practical application of this isomerization technology, no organic solvents were used, and instead, oils and fats were used as the reaction medium. The Z-isomerization of (all-E)-lycopene was promoted by heating (>120 °C) even when oil and fat media were used. Allyl isothiocyanate enhanced thermal Z-isomerization and improved the (5Z)-lycopene content, which shows higher biological activity compared to the other Z-isomers. The thermal isomerization efficiency with AITC was further improved by using certain vegetable oils such as argan and olive oils. In addition, the storage stability of (Z)-lycopene-rich tomato concentrates dispersed in olive oil was evaluated. The total Z-isomer ratio and lycopene concentration decreased with longer storage periods, and it was revealed that (5Z)-lycopene showed excellent storage stability among the mono-Z-isomers.