Effect of apple texture properties and pectin structure on the methanol production in apple wine

The freshly harvested Fuji and Ralls Janet apples were stored in cold storage for 5 months, the texture, pectin content and structure were tracked to explore their effects on the methanol production in apple wine. Results indicated that the flesh firmness of Ralls Janet decreased by 43.31% after five-month storage, its pectin content increased by 576.39 mg/L in juice, and methanol content increased by 59.73 mg/L in corresponding apple wine. Fuji apples have better storage stability, with a 4.34% changes in flesh firmness and a 124.42 mg/L increase in pectin content, corresponding to a 4.11 mg/L increase in apple wine. Compared with pectin Ralls Janet, pectin Fuji possessed more compact conformation, and it was loosened gradually during apple storage. Simultaneously, the broken of pectin main chain and degradation of side chain branches in pectin Fuji was weaker. Correspondingly, the methanol content in wine Fuji increased significantly after four-month storage, while the methanol content of wine Ralls Janet increased by 82.51mg/L after one-month storage. Therefore, apple texture and pectin structure influenced methanol production potential in apple wine making. For easily softened apple varieties, processing should be performed within one month after harvesting to effectively reduce the methanol production in apple wine. • Pectin Fuji had more compact conformation, it was loosened gradually during storage. • The changes of pectin Ralls Janet structures were more severe during storage. • Changes of pectin content and structure in storage affected the methanol production. • Methanol content of wine Ralls Janet increased by 82.51 mg/L by one-month storage. • Judging apple fruits firmness, the risk of methanol in apple wine can be predicted.