Fruits blanching

Fig. 4.3. Survey of freeze dried vegetables and fruits. Blanching time between 2 and 4 minutes (part of Table 1 from [4.11]).

UF is used to clarify various fruit juices (apple, grape, pear, pineapple, cranberry, orange, lemon) which are recovered as the permeate [Blanch et al., AlChE Symp. Ser. 82, 59 (1986)]. UF has also been used to remove pigments and reducing browning in wine production [Kosikowski in Membrane Separations in Biotechnology, McGregor (ed.), Marcel Dekker, New York, 1986]. 

Trimming, cutting, juicing, and blanching of fruits and vegetables... 

Blanching temperatures, holding times, sometimes with the aid of calcium ions or pH shift are manipulated in such a way that the esterases are activated, causing a partial de-esterification of the pectins which then react with (added) calcium ions resulting in stronger intercellular cohesion. To prevent accumulation of methanol in distillates from fermented fruit pulps pectin esterases should be inactivated (59). 

Peroxidase, in combination with phenolic compounds, utilizes hydrogen peroxide to bring about oxidation. The enzymes do not act in intact fruits because of the physical separation of enzyme and substrate. Mechanical damage, rot, or senescence lead to cellular disorganization and initiate decomposition. Inhibition of the enzymes in vegetables is achieved by blanching with steam or by... 

The most common method of thermal pre-treatment is blanching. In this process, wire baskets are used to immerse fruits or pieces of fruit into boiling water. Depending on the species and size of the fruits, the time required for blanching ranges from 10 s to a few minutes (or up to 10 min in the case of quinces). 

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