In-Wook Hwang

Enhancing polyphenol extraction from unripe apples by carbohydrate-hydrolyzing enzymes

The effects of process variables such as enzyme types, enzyme ratio, reaction temperature, pH, time, and ethanol concentration on the extraction of unripe apple polyphenol were investigated. The results indicated that Viscozyme L had the strongest effect on polyphenols extraction and was selected to study the polyphenol composition. The ratio of enzyme (Viscozyme L) to substrate (2 fungal beta-glucanase units (FBG)) at 0.02, reaction at pH 3.7, 50 °C for 12 h, and ethanol concentration of 70% were chosen as the most favorable extraction condition. Total phenolic content (TPC), reducing sugar content (RSC), and extraction yield increased by about 3, 1.5, and 2 times, respectively, compared with control. The contents of p-coumaric acid, ferulic acid, and caffeic acid increased to 8, 4, and 32 times, respectively. The enzyme-aided polyphenol extraction process from unripe apples might be applied to food industry for enhancing bioactive compound production.

Antioxidant capacities and polyphenolics of Chinese cabbage (Brassica rapa L. ssp. Pekinensis) leaves

Chinese cabbage (Brassica rapa L. ssp. Pekinensis) is a green leafy vegetable used mainly in kimchi, salted and fermented dishes. Consumer preference for the leaf portion differs according to the type of dishes. In this study, Chinese cabbage was divided into three parts, and their antioxidant activities were investigated through in vitro assays. The total phenolic contents (TPC), total flavonoid contents (TFC), and vitamin C contents were also determined as indicators of antioxidant contents. The phenolic acids and flavonoids were separated and identified using high performance liquid chromatography (HPLC) and liquid chromatography/mass spectrometry (LC/MS). The outer leaf had the strongest antioxidant activity with the maximum antioxidant contents, followed by the mid- and inner leaves. Principal component analysis (PCA) revealed that outer leaf is positively related to caffeic acid, p-coumaric acid, ferulic acid, and myricetin contents, whereas the mid- and inner leaves are negatively related to sinapic acid contents.

Optimization of enzymatic hydrolysis of persimmon peels for vinegar fermentation

Response surface methodology (RSM) was used to determine the treatment conditions of optimal enzymatic hydrolysis for vinegar preparation from persimmon peel. Persimmon peel was hydrolyzed with different concentrations of Viscozyme L (0–4%) at different temperatures (40–60°C) for different lengths of time (2–10 h) followed by vinegar fermentation. Reducing sugar and soluble solids of the hydrolyzed juice were significantly affected by the hydrolysis conditions. Optimal condition was obtained with the enzyme concentration of 2.38 g/100 mL, reaction temperature of 49.19°C, and reaction time of 6.32 h. The titratable acidity of vinegar prepared from the juice hydrolyzed under the optimized condition increased by 276% (4.25 g/100 g). Acetic acid, citric acid, oxalic acid, and succinic acid were identified in the vinegar. Results suggest that the enzymatic hydrolysis pretreatment could be used for increasing the yield of the vinegar fermentation.

Phenolics enrichment process from unripe apples

Unripe apples contain significant amount of phenolics with various health benefits. A pilot scale enrichment process of unripe apple phenolics with Viscozyme L extraction and XAD-7 sorption process, based on the total phenolic content (TPC), phenolics content by high-performance liquid chromatography analyses, and antioxidant activities were studied. Antioxidant activities were tested by measuring oxygen radical absorbing capacity (ORAC), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, and ferric-reducing antioxidant power (FRAP). The phenolics-rich final product, apple antioxidant phenolics (AAP) has 771-fold higher TPC and 600-fold higher antioxidant activity of unripe apples. Through XAD-7 sorption AAP showed 52, 87, 70 and 44-fold increases in TPC, ORAC, DPPH and FRAP values, respectively. AAP showed more than 95% stability at the temperature range of 20 to 120°… and pH range of 1.47 to 8.5. Apple phenolics extraction process of Viscozyme L extraction coupled with XAD-7 sorption could be applied to the production of health benefit antioxidants.

Quality Characteristics and Volatile Flavor Compounds of Oriental Melon Wine Using Freeze Concentration

In this study, the physicochemical properties, antioxidant capacities, and volatile flavor compounds of oriental melon wine prepared by freeze concentration after heat treatment (HA), ascorbic acid treatment (AAT), and heat and ascorbic acid treatment (HAAT) were investigated. During fermentation period, the melon wine by HAAT showed greater reduction of soluble solids and reducing sugar contents compared to other treatments. In addition, the melon wine treated with HAAT also showed a higher L value and lower browning index compared to other treatments. After aging, free sugar including fructose, and organic acids including citric acid, succinic acid, and malic acid were detected in all samples. For antioxidant activities and contents, HAAT treated wine showed greater antioxidant activities and total phenolic contents than those of others. In GC/MS analysis, a total of 33 volatile flavor compounds were identified. In the principal component analysis of volatile flavor compounds, principal components 1 and 2 repre- sented 88.15% of the whole date distribution and showed opposite tendencies. Taken together, HAAT enhanced the antioxidant activities and sensory properties of oriental melon wine. Moreover, freeze concentration gave the different volatile flavor characteristics in oriental melon wine.