Effect of moderate thermal treatments on the inactivation of a strain of Listeria monocytogenes and physicochemical properties of soursop pulp

Abstract

Soursop ( Annona muricata L.) is a commercially important tropical fruit, whether fresh or processed as a pasteurized or frozen pulp used to prepare juice, drinks, nectar, ice cream, popsicles, and desserts. Besides preserving quality, another preoccupation in the processing of fruit pulps is product safety. Several studies show the association between pulp processing and the development of various microorganisms; however, few have focused on the association between L. monocytogenes and the pulp of sour fruits. The objective was to evaluate the effect of moderate thermal treatments on the inactivation of L. monocytogenes and the physicochemical properties in soursop pulp in order to determine the best processing conditions that will allow to maintain quality as well as to achieve an adequate level of safety. Thermal inactivation kinetics were obtained for L. monocytogenes inoculated in soursop pulp at five levels of temperature (50, 52.5, 55, 57.5, and 60 ℃) and different exposure times (0–60 min). The survival curves did not suggest a log-linear relationship, and were, consequently, fitted to the modified Gompertz equation. The results indicated that the modified Gompertz equation provided an acceptable goodness of fit. Five-log10 cycles reductions of L. monocytogenes were achieved at 50 ℃/60 min, 52.5 ℃/16 min, 55 ℃/10 min, 57.5 ℃/5 min, and 60 ℃/1.25 min. These 5-log10 treatments applied to the soursop pulp indicated that the soursop pulp showed changes in the color parameters and a decrease in the content of total sugars, reducing sugars, ascorbic acid, total phenols, and pH.

Rheological and Physical Properties Affected by the Thermal Processing of Fruit: A Bibliometric Analysis

“…This review summarizes 35 articles that explain the application of different thermal processes, and 21 of these works have addressed the use of conventional thermal treatments [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53]. Table 6 shows a summary discussion about some of the conventional thermal processing techniques used in in natura fruits and in their sub-products, such as flours, juices, pulps, husks, almonds, etc.…”

“…Advancements in thermal processing have allowed for more precise control over heating, so that temperature application can result in improvements in food properties without a loss in their nutritional aspects. Although traditional processes have been developed to preserve food and extend its shelf life without affecting the inherent qualities of food, this objective remains as a major challenge [1][2][3][4].…”