Low-Temperature Preservation of Cherries

Abstract

Cherries (Prunus avium L.) are valued for their taste and nutritional properties. However, they are highly perishable. A low-temperature preservation technology can preserve cherries without spoiling their beneficial properties. This research experimentally substantiated the optimal methods and modes of freezing cherries, defined their refrigerated shelf-life, and identified varieties for low-temperature preservation. The study featured cherries of eight varieties grown in the northern foothills of Dagestan. Fresh cherries served as control. Some cherries were frozen by immersion in a liquid solution of water, alcohol, and sugar (65:20:15) at –24°C. Others were frozen in bulk in air at –30, –33, and –35°C to be stored at –22°C for 3, 9, and 12 months. The nutritional profile was determined by standard methods of chemical analysis. The amount of juice lost during defrosting was assessed by the difference in weight before and after defrosting. The sensory evaluation involved a five-point scale. The best nutritional profile belonged to the sample frozen in air at –35°C while the worst result was observed in the cherries frozen at –30°C. The cherries frozen in bulk in air at –33°C and those immersed in liquid coolant at –24°C demonstrated a poorer nutritional content (by 4.2–5.4%) than the sample frozen in air at –35°C. The sample frozen in air preserved 77.5–81.6% vitamin C, 83.7–89.0% pectin substances, 85.1–88.5% anthocyanins, and 81.4–86.4% sugar after 12 months of storage at –22°C. The sample frozen in liquid coolant retained 75.9–79.0% vitamin C, 84.4–88.2% pectin substances, 83.8–87.5% anthocyanins, and 80.3–84.7% sugar after 12 months of storage. The cherries of the Lezginka, Dagestanka, and Valery Chkalov varieties showed minimal changes after 12 months. The varieties of Buynakskaya, Krupnoplodnaya, and Polyanka could be recommended for nine-month storage. The varieties of Zhemchuzhnaya and Gudzon lost consumer attractiveness as early as after 3 months. When frozen in bulk in air at –33°C and immersed in liquid coolant at –24°C, the cherries preserved their physicochemical properties after 3, 9, and 12 months of storage at –22°C. The study expanded the existing data about low-temperature preservation of cherries and their health benefits.