Strawberry deterioration

Abers, J.E. and Wrolstad, R.E., Causative factors of color deterioration in strawberry preserves during processing and storage, J. Food ScL, 44, 75, 1979. 

Although other dairy products have not been studied extensively, reports suggest that titratable acidity as well as hydrogen ion concentration tend to influence the development of oxidative deterioration. A relationship was found between the titratable acidity and the development of an oxidized flavor in milk (Parks 1974). While milks developed an oxidized flavor at a titratable acidity of 0.19%, the deteriorative mechanism was inhibited when the milks were neutralized to acidities of 0.145% or less. An increase in pH of 0.1 was sufficient to inhibit the development of oxidized flavors in fluid milks for 24 hr (Parks 1974). In addition to fluid milk, Dahle and Folkers (1933) attributed the development of oxidized flavors in strawberry ice cream to the presence of copper and the acid content of the fruit. 

They stressed that the availability of fused silica capillary columns coated with cross-linked non-polar liquid phases permitted development of this technique. Such columns resist the deterioration which was previously encountered with aqueous samples. These authors applied this technique to several citrus essences as well as to fruit essences such as grape, apple and strawberry. 

In considering the possible means by which strawberry color is deteriorated, investigation reveals five significant factors ... 

The most important factor in changing the kinetics of the degradation of color in strawberry products is temperature. The preserver can alter this factor to a limited degree in his choice of manufacturing and storage procedures. The rate of color deterioration increases in proportion to the log of the temperature. Figure 2 shows the relationship graphically. 

Strawberries and sliced bread were purchased from a local market. Damaged, non-uniform, unripe or overripe strawberries were removed and the selected fruits were stored for at least 2 h at 3°C to ensure their thermal equilibrium. Strawberries were selected for this study due to their rapid post-harvest deterioration, which constitutes a problem on their commercial distribution. Sliced bread was selected due to the increasing consumer demand for fresh bread with long shelf-life. 

Figure 4 shows the levels of carvacrol, in terms of peak area counts, reached in the headspace of the containers with bread slices after 0, 2, 5, 10 and 15 days of storage at room temperature. As it can be seen, an increase in the amount of carvacrol released from the PP films was observed with time for the bread samples. A high release of carvacrol was observed at 2 days, being released more slowly after 5, 10 and 15 days of storage. This mechanism of controlled release could lead to shelf-life improvement of the stored samples retarding the post-harvest deterioration. This behavior was also observed for strawberries. Regarding the thymol release, a similar trend was shown for both test food samples. 

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