Studies on the Freezing of Green Plantains (Musa paradisiaca) II. Sulfitation to Control Browning

Abstract

The SO₂ content of green plantain slices sulfited in metabisulfite solutions increases with dipping time, but not in direct linear relationship. Increasing the concentration of the dipping solution resulted in a proportional increase in the SO₂ content. Lowering the pH of the sulfiting solution resulted in higher SO₂ uptake. Sulfurous acid solutions at pH 2.2 gave the higher SO₂ content at a given clipping time. When sulfiting plantain slices in K₂S₂O₅ solutions at pH 3.3, blanching increases the bisulfite absorption. Sulfiting in sulfurous acid solutions resulted in higher levels of SO₂ in hand peeled unblanched slices and lowest in steam peeled and blanched slices. The SO₂ content increased with the length of the blanching treatment for both water and steam blanching. Increasing the temperature during water blanching from 71.1° C (160° F) to 93.3° C 200° F) had no appreciable effect on the SO₂ content. When slices were sulfited in K₂S₂O₅ solutions, the loss of SO₂ during frying was greater in blanched fruit, either hand- or steam-peeled. When the slices were sulfited in sulfurous acid solutions, the greater loss of SO₂ during frying occurred in steam peeled fruit and neither the blanching method used nor the temperature had any effect on the SO₂ loss. Sulfiting to levels of 100-150 p/m SO₂ proved effective in controlling browning. The loss at this level during frying amounted to 50-60 percent, leaving a residue of SO₂ which could not be detected by tasters, and did not affect the flavor of the product.