Effect of different juicing methods on quality of pomegranate wines

Abstract:【Objective】Pomegranate is one of the most popular fruits because it has an exotic flavor and is a kind of nutrient-rich fruit, with abundant amount of sugars, organic acids, vitamins, amino acids, and polyphenols. Pomegranate wine is one of important products of pomegranate, which is a low-alcohol fruit wine made through fermentation and aging, and retains the original flavor and nutrition of pome- granate. The pomegranate wine is mostly processed from fresh pomegranate with peeling and separating pomegranate seeds. However, the process of removing and separating pomegranate seeds is complicat- ed, requires high-class equipment, and takes a long time. It is vulnerable to microbial pollution so that the safety and health could not be guaranteed. Therefore, it is necessary to figure out a pretreatment method of making pomegranate wine to provide reference for optimizing pomegranate wine process and improving thewine quality.【Methods】Fresh pomegranates were used as raw materials to investigate the effects of five different juicing methods on the physicochemical properties, antioxidant capacity, flavor components and sensory quality of pomegranate wine. The pomegranate wine was respectively ferment- ed from pomegranate juice without seeds, pressed pomegranate juice with pectinase, pressed pomegran- ate juice with seeds, pomegranate juice with crushed seeds, and pomegranate juice with inner dia- phragm.【Results】The contents of alcohol, total sugar, reducing sugar, total acid, dry extract and metha- nol of pomegranate wine fermented by different juicing methods were 12.45%-12.85%, 2.41-6.01 g·L-1, 2.16-5.24 g·L-1, 3.11-3.77 g·L-1, 17.80-25.89 g·L-1, 19.84-125.38 mg·L-1, respectively. The alcohol con- tent could meet the requirements of GB15037—2006“wine”. The methanol content was all lower than the methanol content (≤400 mg · L- 1) stipulated in GB 15037—2006“wine”. The contents of reducing sugar (5.24±0.10 g·L-1) and total acid (3.77±0.00 g·L-1) in wine fermented from pomegranate juice with inner diaphragm were significantly higher than those in other fermented wines. The content of dry ex- tract of wine fermented from pomegranate juice without seeds was significantly lower than that of other four kinds of pomegranate wine with seed (17.80±0.71 g·L-1). The phenolic substances in pomegranate wine had a strong antioxidant efficacy, which had an important influence on the quality of pomegranate wine. The contents of total phenols, total flavonoids and anthocyanins in fermented pomegranate wine were 455.4-1 223.79 mg·L-1, 253.82-1 178.82 mg·L-1 and 0.22-6.03 mg·L-1, respectively. The anthocyan- in contents of 5 fermented wines were significantly lower than the content of fresh pomegranate juice, because anthocyanins could be degraded or transformed during the fermentation of pomegranate wine. Wine fermented from pomegranate juice with inner diaphragm had higher contents of total phenols and total flavonoids as well as potent scavenging capabilities towards 2, 2-azinobis(3-ethylbenzothiazoline-6- sulphonic acid)diammonium salt (ABTS) cationic radicals and superoxide anion radicals, which was 4.35-5.60 times and 10.27-12.08 times higher than those of the other four fermented wines, respectively. Aroma component was the direct influencing factor of sensory evaluation of fruit wine, and also a signif- icant index to evaluate the quality characteristics of fruit wine. The flavor substances in five pomegran- ate wines were identified by headspace solid phase micro-extraction and gas chromatography-mass spec- trometry technology. Thirty two flavor components were identified from five pomegranate wines, including 17 kinds of ester compounds, 4 kinds of alcohols, 2 kinds of acids, 3 kinds of aldehydes and ketones, 4 kinds of terpenes, and 2 kinds of aromatic hydrocarbon compounds, with contents ranging from 0.008 mg·L-1 to 26.417 mg·L-1, among which esters and alcohols were the most abundant compounds. Differ- ent juicing methods had great influence on the types and contents of aroma compounds in fermented pomegranate wine. The wine fermented from pomegranate juice with inner diaphragm contained higher level of esters, whereas the wine fermented from pomegranate juice with uncrushed seeds and crushed seeds contained higher level of alcohols. Based on the odor-activity analysis of pomegranate wine, the contents of isopentyl acetate, octanoic acid ethyl ester, acetic acid phenyl ethyl ester and decanoic acid ethyl ester were higher, which had higher odor-activity value, made a major contribution to the wine aro- ma, and reflected enjoyable floral, fruity and sweet aroma. Based on sensory evaluation, wine fermented from pomegranate juice without seeds was bright red, clear, transparent and lustrous, with pomegranate aroma, harmonious and pure taste, and good overall balance, which hence got the highest score. The seeds and septum of fresh pomegranate could affect the clarity, aroma and taste of fermented pomegran- ate wine. Before drinking, wines fermented with seeds and septum needed to be clarified, mixed and sub- sequently processed.【Conclusion】The wine fermented from pomegranate juice without seeds was most acceptable to the consumer, while the wines fermented from pomegranate juice with inner diaphragm had prominent antioxidant abilities, relatively rich aroma, and simple processing technology, which might be more promising for a large scale production of pomegranate wine .