Enhancing Effect of Cooking of Fermented Tomato Sour Soup with Added Oil on Lycopene cis/trans Isomerization

In this study, we evaluated the cis/trans-lycopene content in commercial ketchup, and investigated the effect of cooking of fermented tomato sour soup added with one of seven oils including peanut oil (PO), sesame oil (SO), corn oil (CO), tung seed oil (TSO), olive oil (OO), Litsea cubeba oil (LCO), and mustard oil (MO) on lycopene isomerization. The results showed significant differences in the contents of total lycopene and cis-lycopene among six brands of ketchup (P < 0.05), with cis-lycopene accounting for only 20.84%-24.56% of the total lycopene. The contents of total lycopene and cis-lycopene were significantly different among the seven cooked fermented tomato sour soup samples (P < 0.05), and their proportions of cis-isomers (51.40%-78.23%) were 1.2-1.9 times higher than that of the blank group and 2.09-3.75 times higher than those of the six brands of ketchup. Specifically, the sample with added MO had the highest proportion of cis-lycopene (78.23%), followed by those with SO and PO (75.34% and 71.65%, respectively). The total lycopene and cis-lycopene contents of the sample with added PO were 6.6 and 11.4 times higher than those of the blank control group, respectively, indicating that the former has great market potential. Therefore, the results of this study could provide a scientific basis for the further processing of fermented tomato sour soup for high-value functional products.