CLARIFICATION AND GELATION OF A MINIMALLY HEATED ORANGE JUICE CONCENTRATE DURING ITS REFRIGERATED STORAGE

The refrigerated storage of orange concentrates low in pulp content could be an interesting procedure of preservation of concentrates not submitted to high temperature treatments. Orange concentrate of 42°Brix with low pulp content, treated at a very low temperature (60C for 15 s) to avoid microbial spoilage, was stored for 6 months at 3C. The losses of cloudiness during the storage were higher than that of the single strength juice also treated at 60C for 15 s. Gelation of concentrate was detected initially, being the storage modulus higher than the loss modulus at the end of the first month of storage. In any case, the degree of gelation observed after 6 months was far from the substandard quality, according to Florida Statutes. The clarification of this orange concentrate is the factor limiting of its shelf life. Consequently, experiences using heat treatments slightly higher must be planned to delay the loss of cloudiness. PRACTICAL APPLICATIONS Citrus juice industries use to store concentrates of different characteristics (color, °Brix/acid ratio) that are later blended in proper proportions to obtain final products with uniform characteristics. Refrigerated concentrates are easily handled but pectin methylesterase (PME) activity can damage them and, thus, frozen storage is preferred. As PME is associated with cell walls, its activity should be reduced by removing part of the pulp. This paper analyzes the effect of the residual PME activity on colloidal stability of low pulp content concentrates measured by the losses of turbidity and the changes in rheological properties.