Mechanism of Chilling Injury in Sweet Potatoes Part V

Abstract

1. The ratio of the unsaturated C16, C18 and C20 fatty acids to total fatty acids was higher in the crude mitochondrial fraction from chilling-stored sweet potatoes 4 days after transfer to 0°C than from healthy sweet potatoes; and, the difference became greater at periods of 7, 10, and 14 days. However, this difference was shown to be mainly due to the decrease during chilling storage in contamination with lauric acid, isopalmitic acid (presumable) and erucic acid (presumable) contained in the latex body fraction. 2. There were no significant changes in the composition and amounts of fatty acids in the 0_??_700×g fraction, the microsomal fraction, and the supernatant fraction, when sweet potatoes were given a chilling treatment. 3. The ratio of C16, C18 and C20 unsaturated fatty acids to total fatty acids in the pure mitochondrial fraction from sweet potatoes was not changed significantly as a result of chilling storage. However, the ratio of lipid-phosphorus (lipid-P) to acid insoluble nitrogen (acid insol.-N) decreased during chilling storage, and the density of the mitochondria was slightly heavier as revealed by sucrose density gradient centrifugation. 4. The composition of fatty acids, the ratio of lipid-P to acid insol.-N, and the density of the pure mitochondrial fraction from white potatoes was not distinctly changed as a result of chilling storage. 5. Contrary to previous reports, white potato, a temperate-zone plant, had a lower ratio of unsaturated fatty acids to total fatty acids in the pure mitochondrial fraction than in the case of sweet potato, a tropical plant.