The Grade of Dried Jujube (Ziziphus jujuba Mill. cv. Junzao) Affects Its Quality Attributes, Antioxidant Activity, and Volatile Aroma Components

Abstract

Jujube (Ziziphus jujuba Mill. cv. Junzao) has attracted a large number of consumers because it is rich in nutrients, such as carbohydrates, organic acids, and amino acids. Dried jujube is more conducive to storage and transportation, and has a more intense flavor. Consumers are affected by subjective factors, and the most important factor is the appearance of the fruit, including size and color. In this study, fully matured jujubes were dried and divided into five grades according to their transverse diameter and jujube number per kilogram. In addition, the quality attributes, antioxidant activities, mineral elements, and volatile aroma components of dried jujube were further analyzed. As the dried jujube grade increased, the total flavonoid content increased, which was positively correlated with the antioxidant activity. The results showed that small dried jujube had a higher total acidity and lower sugar–acid ratio than large and medium dried jujube, thus, large and medium dried jujube had a better flavor than small dried jujube. However, the antioxidant activity and mineral elements of medium and small dried jujube were superior to large dried jujube. From the edible value analysis of dried jujube, medium and small dried jujube were better than large dried jujube. Potassium is the highest among the measured mineral elements, with contents ranging from 10,223.80 mg/kg to 16,620.82 mg/kg, followed by Ca and Mg. Twenty-nine volatile aroma components of dried jujube were identified by GC–MS analysis. The main volatile aroma components were acids including n-decanoic acid, benzoic acid, and dodecanoic acid. The fruit size affected the quality attributes, antioxidant activity, mineral elements, and volatile aroma components of dried jujube. This study provided a piece of reference information for further high-quality production of dried jujube fruit.