Food Research International 27 (1994) 545-553 Shelf-stable high moisture papaya minimally processed by combined methods A. Ldpez-Malo, E. Palou, J. Welti, P. Code & A. Argaiz Departamento de Ingenieria Q&mica y de Alimentos, Universidad de las AmPricas-Puebla, P.O. Box 100, Sta. Catarina Mcirtir, Cholula (72820), Puebla. Mexico A preservation process to achieve microbial and sensorial stability of papaya slices stored at 25°C at least during five months was developed. The preserva- tion process was based on ‘combined methods technology’, and included the combination of the following factors: a mild heat treatment (blanching), a water activity reduction, a pH decrement, and the addition of potassium sor- bate and sodium bisulfite. The obtained fruit stored at 5 and 25’C during five months was evaluated for color and texture changes, sulfite and potassium sor- bate degradation kinetics, changes of aerobic plate counts, yeasts and molds, ascorbic acid retention and sensorial quality changes. Moisture and soluble solids contents, pH, and water activity remained almost constant and the product obtained was microbiologically sound during storage. There was an enzymatic sucrose hydrolysis that reduced the water activity more than expected, which helps to assure the microbial stability. Total sulfite and potassium sorbate concentrations were reduced during storage at 5 and 25°C giving final concentrations 62 and 66%, and 40 and 60% of the initial concen- trations, respectively. Ascorbic acid content of papaya was reduced during pro- cessing and storage. Color, texture and sensory evaluation reveal that there were no significant differences between samples stored at 5 and 25°C. The pa- paya slices obtained showed a good overall acceptability (initial mean score 7.25) even after five months of storage at 25°C (final mean score 6.73) Keywords: Papaya, combined methods, storage stability. INTRODUCTION Fresh tropical fruits are an important component of the diets of the people of the tropical regions. Besides being liked for their exotic flavor and color, they are rich sources of vitamins, especially the provitamin A carotenoids and vitamin C, minerals, carbohydrates and as such constitute an important element of human nutrition (Jayaraman, 1988). ‘World production of major tropical fruits of economic importance such as banana, mango, pa- paya, pineapple, and others of lesser importance like guava, sapota, etc., is mostly spread over the tropical and subtropical zones of less developed countries of which Mexico occupies an important place (in 1983 Mexico harvested around 11.5% of world production of papaya). The absence of ade- Food Research International 0963-9969/94/%07.00 0 1994 Canadian Institute of Food Science and Technology quate modern facilities for handling, transporta- tion, and storage of these highly perishable com- modities (Jayaraman, 1988; Alzamora et al., 1989, 1993) and the lack of technical training and infra- structure for their processing and preservation, causes a loss of around 30% in production and in some cases in excess of 50% (Argaiz et al., 1991). There is, therefore, a growing and urgent need for simple inexpensive processes alternative to re- frigeration, freezing and other processing methods intensive in energy expenditure and capital invest- ment, that would offer a way to save these highly perishable commodities from spoilage under tropi- cal conditions and make them available to regions away from places of abundant production and during lean seasons (Jayaraman, 1988; Argaiz et al., 1991; Alzamora et al., 1993). Intermediate moisture fruit products, appear to have potential markets (Karel, 1976; Chirife, 1982; Levi et al., 1985). However, the application of 545