One way of achieving this is by homogenizing the juice. Pulp volume may be increased by transferring it from tomato products where syneresis is not a problem, and by changing the shape of the particles so that they will occupy a larger volume. From a technological point of view, increasing the pulp volume and the strength of the interparticle bonds is the key for preventing syneresis. Preventing syneresis in tomato juice presents a challenge since no additives are allowed. ![]() The formation of an undesired clear serum layer has been a serious problem ever since tomato juice was bottled in transparent packages. This is how syneresis is observed in tomato juice. If not strong enough, rearrangement of these pulp particles, mainly under gravitational forces, may produce a visible separation between the precipitating pulp and the clear serum. The suspended pulp occupies the whole volume and the interparticle interaction provides the bonds that stabilize that system. Tomato juice is a weak particulate gel of pulp particles that are suspended in a serum containing soluble sugar, salts, acid and polymers ( Mizrahi, 1997). Mizrahi, in Chemical Deterioration and Physical Instability of Food and Beverages, 2010 11.4.4 Tomato juice The RO tomato juice concentrate is characterized by improved color and flavor. However, a rejection of 99% or more of tomato juice solids has been recorded. The rejection of the tomato juice solids is little affected by the quality of the fruit and the operating conditions. ![]() The different tomato juice concentrates – sauces (8–12 Brix), passata (16 Brix), and pastes (27–28 or 37–38 Brix) – can then be made from RO concentrate by evaporation. Several plants are now concentrating tomato juice by RO from 4.5–5.0 to 8 Brix. This unusual behavior has been attributed to the rheological properties of tomato juice. It is of interest to note that changing feed velocity has a small affect on flux. The different parameters for RO of tomato juice have been optimized. The advent of the new generation of RO thin-film composite membranes enabled food processors to concentrate tomato juice using RO on a commercial scale. However, this method has not been applied commercially. ![]() Early attempts at concentrating tomato juice by RO were based on removal of the suspended material (mainly dietary fiber) by centrifugation or ultrafiltration, concentrating the clear serum by RO, followed by mixing the concentrate with the insoluble precipitate or concentrate. However, the quality of the tomato juice has little effect on its behavior during RO processing. Tomato juice is a very variable material depending on the fruit variety, soil, and climatic conditions and processing conditions. Abd El-Salam, in Encyclopedia of Food Sciences and Nutrition (Second Edition), 2003 Tomato Juice
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