Concentration of citrus fruit juices in membrane pouches with solar energy Part 2: How solar drying setup and juice pretreatment determine the microbiological quality

The aim of this study was to investigate how solar drying setup and choice of juice pretreatment determine the microbiological quality in a fruit juice concentration process called solar assisted pervaporation (SAP). With this process, hygienic membrane pouches and solar energy are used to concentrate and preserve fruit juices. In this study, citrus (tangerine) marmalades were produced with SAP membrane pouches under realistic conditions in rural Mozambique with three solar drying setups and eight juice pretreatments. The results showed that the choice of solar drying setup had a negligible effect on the total aerobic plate count but a significant effect on the yeast plate count. Pasteurization as a juice pretreatment lowered the total aerobic count and the probability of fermentation, while lemon juice had no beneficial effect on the microbiological quality. The recommendations are to add sucrose and pasteurize the juice before drying and to use a direct active solar dryer. Practical Applications: Solar drying is a sustainable approach to food preservation for the future. However, there are food safety challenges with solar drying that make the process difficult to control. One challenge is the direct contact between the product and the surrounding air since the air may be contaminated with microorganisms. One approach to reduce the probability of contamination is by solar drying fruit juices with membrane pouches that provide a hygienic barrier between the product and the surrounding air. These types of pouches are especially suitable for juicy, citrus fruits that are difficult to preserve with traditional solar drying practices. The pouches can be used to concentrate citrus juices into marmalades in rural areas of tropical countries where established infrastructure is not available. This study investigated the hygienic nature of the approach in rural Mozambique with the help of small-scale producers to determine the optimal way to produce safe marmalades.