The Storage Life of Refrigerated Grape Juice Containing Various Levels of Sulfur Dioxide

Abstract

Shelf life at 5°C was determined for 135 grape juices treated with 0, 100, 200 and 300 ppm SO₂. Of the untreated samples, 85% fermented within five weeks compared to a rate of 13% in 30 weeks in the presence of 100 ppm SO₂. Only three juices treated with 200 ppm SO₂ and two treated with 300 ppm fermented during 30 to 35 weeks of storage. Examination of 13 nonfermented juices treated with 200 ppm SO₂ revealed all to be negative for viable yeasts at the end of this period. The sulfited juices that had fermented had initial yeast populations of 10⁶/mL or greater. Settling of juices for 26 hours reduced viable yeast populations by 54 to 96% and thus might be a practical control procedure. The addition of 200 ppm SO₂ appeared to be the optimal treatment since it completely inhibited mold growth and prevented fermentation of most samples. It was concluded that the combination of SO₂ plus a low storage temperature is feasible for the preservation of Eastern grape juice providing that yeast contamination is not excessive.