Modifying water activity and acidification lead to refreshing fruit drink.

Passion fruit, which comes from a tropical plant, has a peculiar intense taste and high acidity levels. Minimal processing preserves the fresh characteristics of the fruit, as well as its essential nutriments, such as heat-sensitive vitamins and pigments. Passion fruit is rich in vitamins A and C and is a good source of potassium and iron. The seeds are high in fiber.

The objective of Mexican scientists was to carry out microbiological and sensory analyses of minimally processed passion fruit pulp. They wanted to determine the characteristics of a refreshing drink based on the concentrated fruit.

Four formulations of fruit pulp were developed and packaged in polyethylene plastic films and glass jars. These were stored at 4 C and 25 C. The formulations included natural extracted pulp; pulp with a water activity ([a.sub.w]) of 0.96 with the addition of sucrose; pulp obtained at 2 pH, which was then modified to pH 3 with citric acid; and pulp obtained at 3 pH with 1000 ppm of potassium sorbate.

The researchers evaluated microbial growth--total plate count, coliforms, molds and yeasts--during the storage period. A consumer preference test was carried out based on the hedonic scale. The test compared a fresh juice-based beverage with one based on reconstituted minimally processed pulp with water.

Combining an [a.sub.w] of up to 0.96 with sucrose, then acidifying the mixture to pH 3.6 and adding 1000 ppm of potassium sorbate, yielded the best drink. No microbial growth problems appeared during the research. As a matter of fact, there were less than 100 CFU per ml. The formulation at 4 C was generally accepted as a good product. The combined techniques used were able to preserve the fruit for up to 15 weeks at a storage temperature of 4 C, and for four weeks at 25 C.

Further information. C. Santacruz-Vazquez, Universidad Autonoma de Puebla, 4 Sur 104, Col. Centro, CP 72000, Puebla, Mexico; phone: +52 (01 222) 2 29 55 00; URL: www.buap.mx.