Sulfur-Containing Compounds: Natural Potential Catalyst for the Isomerization of Phytofluene, Phytoene and Lycopene in Tomato Pulp

Vegetables containing sulfur compounds promote trans-isomerization of unsaturated fatty acids in triacylglycerols during the cooking process

Growing evidence indicates that the intake of trans-fatty acids (TFAs) has been associated with a higher risk of cardiovascular disease; therefore, various industrial measures have been taken to reduce the amount of TFAs consumed. However, research on TFAs formed during cooking is limited. Isothiocyanates and polysulfides, which are widely distributed in various vegetables, have recently been shown to promote the cis-trans isomerization of double bonds. However, the effects of these sulfur compounds on unsaturated fatty acids (UFAs) comprising edible oils (triacylglycerols) are unknown. To further reduce the intake of TFAs, a better understanding of the effect of the presence of these sulfur compounds on the formation of TFAs under cooking conditions is important. This study investigated the isomerization characteristics of UFAs in the presence of isothiocyanates and polysulfides in model systems using high-purity compounds as well under simulated cooking conditions using food samples. The outcomes of the model system indicated that these sulfur compounds significantly enhance the thermal isomerization, especially at temperatures ≥140 °C. Furthermore, the addition of antioxidants substantially inhibited the isomerization enhancement effect of isothiocyanates, whereas that of polysulfides was marginally moderated. A similar trend was observed under simulated cooking conditions. The results suggest that cooking with sulfur-compound-rich vegetables, especially garlic and onion, which are rich in polysulfides, can potentially result in increased trans fatty acid intake.

Lycopene in hydrophobic deep eutectic solvent with natural catalysts: A promising strategy to simultaneously promote lycopene Z-isomerization and extraction

Lycopene Z-isomerization and degradation in a series of hydrophobic natural deep eutectic solvents (HNDES) was firstly studied. The highest lycopene retention (about 84.6%) was found in HNDES composed of thymol and menthol (TM), and fatty acid-based HNDES promoted lycopene Z-isomerization (about 70% for total Z-isomers) and degradation. The addition of allyl isothiocyanate (AITC), diallyl disulfide (DADS) and capric acid into TM promoted Z-isomerization of lycopene (80% for total Z-isomers), especially 5Z-isomer (>30%), while lycopene remaining rate in TM/-capric acid was below 20%. During lycopene extraction from tomato power and watermelon juice by TM, the ratios of Z-isomer significantly (p < 0.05) increased especially with AITC and DADS (up to about 80%), and extraction yields increased even > 100% with capric acid. Lycopene in TM/-capric acid extracts showed low degradation with Z-isomers increasing during storage. TM with capric acid could simultaneously promote lycopene Z-isomerization and extraction.

Study on the Drying Technology of Tomato Pulp with Phytoene, Phytofluene and Lycopene Retention as Inspection Indexes

The objective was to design a feasible drying method to increase the retention rates of phytoene (PT), phytofluene (PTF) and lycopene (LYC) in tomato powder. The method was to compare the effects of vacuum freeze-drying (FD), vacuum drying (VD) and hot-air drying (HAD) technologies on tomato pulp rich in PT, PTF and LYC. When dried by HAD, the retention rates of PT, PTF and LYC decreased significantly (p < 0.05) only when the water content decreased from 30% to 3.5%. When dried by VD, the temperatures had no significant effect on the retention rates, and only alkaline conditions (pH = 9), Fe3+ and Al3+ could significantly reduce the retention rates (p < 0.05). Therefore, a combined drying process (CDP) was designed: before the water content decreased to 50%, HD (60 °C) technology was used; then, the paste was dried via VD (80 °C, 0.08 MPa) technology till the water content reached 5 ± 2%; loading weight was 40 g (thinkness 5.70 mm) for each batch. Compared with VD alone, the CDP technology improved the retention rates of PT and LYC by 12% and 36%, respectively, while PTF decreased by only 6%.