Assessment of the Suitability of Guava Fruits for Use in Ketchup and Evaluation of its Antioxidant Activity in vitro

Abstract

　To examine the possibility of using guava fruits as an ingredient in daily-use ketchup with food functionality, we prepared purees of eight pink guavas that were obtained from different areas in Okinawa and their chemical and physical compositions by measuring the Brix, pH, and color. The eight kinds of guava purees showed little difference in their compositions, Brix, pH, and color values. In addition, the purees maintained their color values after heating at 80℃ for 5 min. The guava puree was then treated with pectinase to decrease the puree viscosity. The viscosity of the puree treated with pectinase (0.24 Pa・s) was lower than that of the untreated puree (0.6 Pa・s). The guava ketchup was prepared using the untreated guava puree. In the sensory evaluation, the guava ketchup scored low for sourness because the citric acid content was lower than that in the commercial tomato ketchups. To evaluate the antioxidant activity, guava ketchups prepared using guava purees with and without pectinase treatment (GK-P and GK, respectively) were examined for total polyphenol contents and DPPH radical-scavenging activities. The total polyphenol content and DPPH radical-scavenging activities were higher in guava ketchups than in the commercial tomato ketchups. Interestingly, GK-P showed significantly higher radical-scavenging activity than GK. These results suggest that guava fruits have the potential to be used in the manufacturing of ketchup, which could serve as an antioxidant food.