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Compositional changes during ripening impact fruit quality.

Compositional changes that occur as fruit ripens affect both the organoleptic and nutritional quality of small fruit. Understanding these developmental changes may help us optimize the quality of the product.

Canadian scientists harvested blueberry (Vaccinium corymbosum L.) and cranberry (Vaccinium macrocarpon Aiton) fruit at three maturities--white, turning and fully colored--from commercial fields during two seasons. The investigators then analyzed the composition of the fruit to determine sugar and acid content; total phenolics; total anthocyanins; oxygen radical absorbance; antioxidant capacity; and fruit firmness.

The researchers found that in blueberry fruit, the primary sugars were glucose and fructose, whose levels increased from about 2% to 6% as the fruit ripened from white to blue color. Citric acid comprised 60% to 80% of the organic acids in blueberries and declined by 60% as the fruit ripened from white to blue.

There were additional acids present, including quinic, malic and small amounts of succinic and tartaric acids. Total blueberry phenolics in the turning fruit were 60% less than in white fruit and 12% less than in blue fruit. Anthocyanins increased as color developed. Antioxidant capacity declined as the fruit ripened from white to turning. Firmness decreased about 80% as fruit ripened from white to blue.

The composition of cranberry fruit did not change as extensively as blueberries did during the ripening process. Sugar concentration increased from about 2.2% to 3.2% as the cranberry fruit ripened from white to red color, with glucose comprising 82% to 74% of the total sugars. During the same time, acid content decreased by only 22%.

Citric acid comprised more than 50% of the acids in white cranberry fruit, but its level declined to about 30% in ripe fruit. Meanwhile, levels of quinic and malic acids increased to 30% and 40%, respectively. Similar to blueberries, total anthocyanin content increased in cranberry as color developed. Total phenolics and antioxidant capacity remained relatively constant. In contrast to blueberries, the red cranberry fruit was firmer than white or turning fruit.

Further information. Charles Forney, Ph.D., Research Scientist, Postharvest Physiology, Agriculture and Agri-Food Canada, Atlantic Food and Horticulture Research Center, 32 Main St., Kentville, NS B4N 1J5 Canada; phone: 902-679-5714; fax: 902-679-2311; email:
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Publication:Emerging Food R&D Report
Date:Aug 1, 2013
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