This study investigated the yellowing phenomenon of maesil (Prunus mume), changes in organic acid (OA), and cyanogenic glycoside (CN-Glc) contents during post-harvest ripening, and the potential use of ripened maesil as raw material for CN-Glc-reduced maesil chungs. Ripening conditions were as follows: 5℃ for Ripening I, 20–22℃ with 50–60% RH for Ripening II, 20–22℃ with 50–60% RH after ultrasonic washing of maesil for Ripening II-US, and 35℃ and 80–90% RH for Ripening III. Yellowing did not occur in maesil under Ripening I even after 7 days, but was observed after 7 days of Ripening II and Ripening II-US, and after 3 days under Ripening III. The OA content slightly decreased under all ripening conditions, while CN-Glc content significantly decreased, with ripening under all ripening conditions, with Ripening II and Ripening II-US being the most effective at reducing CN-Glc levels. In maesil chungs prepared from ripened maesil CN-Glc content was significantly lower than that of those made with untreated maesil. These results demonstrate that ripening under the conditions tested in this study significantly reduces CN-Glc content in maesil with minimal reduction in OA content, enabling the preparation of CN-Glc-reduced processed maesil products.

This study investigated the changes in the cyanogenic glycoside (CN-Glc) content of maesil chung (MC) prepared according to its preparation conditions (i.e., maesil part, sugar type, maesil-sugar mixing ratio, liquid separation) and sugaring-ripening period and the quality characteristics of their products finalized through filtration and heat treatment (85oC, 30 min) with the 6-month ripened MC. The CN-Glc content dramatically decreased when the maesil flesh, isomaltooligosaccharide, maesil:sugar ratio of 5:5, and liquid separation after the 4-month sugaring were applied to the MC production. The CN-Glc content decreased with the ripening period. There was no effect of filtration and heat treatment on the CN-Glc reduction of the MC product. The sugar type predominantly affected the soluble solid and total carbohydrate content of the MC products, and their contents increased in the order of high-fructose corn syrup > sucrose > isomaltooligosaccharide. The MC product at a maesil:sugar ratio of 6:4 exhibited the higher organic acid content. There was no direct association between the total polyphenolic compound content and the preparation conditions of the MC product. Overall, the use of maesil flesh as a maesil ingredient and more than 6-month ripening after liquid separation may be a pivotal factor in producing the cyanogenic glycoside-reduced maesil chung.

This study compares the amygdalin content and quality characteristics of maesil chung prepared with different maesil cultivars. Maesil fruits were sugared for 3 months, aged for 3 months after the liquid separation, and heat treated at 75oC for 30 min. Amygdalin in maesil chung generally peaked at the second month of sugaring and gradually decreased until three months of sugaring. During the first month of aging, amygdalin dramatically decreased and then gradually decreased by additional aging for two months. For the end-use maesil chungs (subjected to heat treatment), the amygdalin content ranged from 68.5 to 179.4 ppm, the soluble solid content from 58.8 to 62.3 oBrix, and the 5-HMF from 3.5 to 13.4 ppm. Their color characteristics exhibited a brightness of 26.8-27.6, a redness of 9.4-10.5, and a yellowness of 5.3-6.9. Their total sugar content was in 34.2-44.7%, consisting of 1.8-2.1 mg/mL glucose, 1.6-2.0 mg/mL fructose, and 1.3-1.9 mg/mL sucrose. Only malic acid and citric acid were detected in the enduse maesil chungs. While the trace amounts of Na and Fe were found, K, P, and Ca were relatively rich.