An Examination of the Importance of Anaerobiosis and Ethanol in Causing Injury to Grape Mitochondria

Mitochondria from grape berries were extracted and purified in order to examine mitochondrial activity with respect to anaerobiosis and ethanol concentration. Malate and pyruvate must be oxidized together by aerobic grape mitochondria due to the lack of malic enzyme in this compartment. The respiration of these substrates is highly coupled to phosphorylation. Data reported in the literature on the respiration of the whole berries at 30-degrees-C were the same as the rates of respiration measured on phosphorylating isolated mitochondria. This and other results strongly suggested that a partial anaerobic metabolism may be present in aerobic fruits subjected to heat stress during maturation. The duration of mitochondrial viability during a complete anaerobiosis of fruits was dissimilar from one berry to another, among different cultivars, and for different dates of grape harvest. Ethanol uncoupling effect and its reversibility on grape mitochondria were significant for concentrations that are usually obtained when anaerobic metabolism is achieved during carbonic maceration.