Strawberries preserves

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. 

For variety, try using some orange marmalade, raspberry or strawberry preserves, or even a tablespoon of frozen red or purple grape juice concentrate in place of sugar or other sweeteners. Combining the flavors of fruit with cocoa just can t be beat ... 

It has been known for decades that heat is one of the most destructive factors of anthocyanins in berry fruit juices (Jackman et al., 1987a). With strawberry preserves, it was shown as early as 1953 that the half-life time was 1 h at 100°C, 240 h at 38°C and 1300 h at 20°C. In a storage experiment with concentrates and dry powder of elderberry extracts, the stability increased 6-9 times when the temperature was reduced from 20°C to 4°C (Zajac et al., 1992). Anthocyanin degradation in anthocyanin solutions increased from 30% to 60% after 60 days when storage temperatures were increased from 10°C to 23°C (Cabrita et al., 2000). High-temperature short-time processing is recommended for maximum anthocyanin retention of foods containing anthocyanins (Jackman and Smith, 1996). 

The relative merits of sucrose, dextrose, and corn sirup as a food preservative from the standpoint of color and flavor retention have been investigated by several workers. Using frozen peach slices (18, 118, 116), strawberry preserves (110), and frozen blackberries and raspberries (17), the following results were observed (1) Replacement of part of the sucrose by dextrose resulted in poorer color of frozen peaches and (2) replacement of 25 to 50% of the sucrose with corn sirup produced detectable changes in flavor in all the cited foods. 

Strawberry preserves represent about 26% of all fruit preserve flavors, or about 12% of the total production of all fruit spreads, and consequently the largest volume of a single variety of fruit spread in the country. 

Some of the concentrate was diluted back to single-strength strawberry juice and saturated at room temperature with sucrose. This mixture (St S) closely simulates the composition of a finished strawberry preserve. 

Figure 2. Effect of Temperature on Half Life of Color in Strawberry Preserves...

At room temperature (20° C.), the half life of the color of strawberry preserves is about 1300 hours. In the summertime, the grocery shelf in the front of the corner grocery store may reach 38° C., at which temperature the half life drops to 240 hours. It is possible to increase the life of the color in the finished preserves six or seven times over room temperature storage by storing under egg storage conditions (4° C.), where half life is extended to 6000 to 8000 hours (250 to 320 days). 

The susceptibility of ascorbic acid to oxidation has long been known, but it is surprising to note its stability when strawberry preserves are made by vacuum processing methods. 

With this general background, some work has teen carried out on the effect of low concentrations of sucrose and, in some cases, dextrose on the flavor of cooked foods which are commonly seasoned with butter, salt, and pepper. In earlier studies of various sweeteners, sweet taste was a flavoring, since it was predominant in the flavor of the strawberry preserves (10), frozen peaches (5), red raspberries, blackberries U), and strawberries. In addition, it counteracted some of the inherent sourness and enhanced natural fruit character. The following studies were designed to test the potentialities of sweeteners as seasonings. 

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