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Technological Research on Preparation of High Activity Walnut Pulp by Ultrasonic-compound Enzyme Synergistic Method

Author: LiuYaBin
Tutor: ChenShuJun
School: Shanxi University
Course: Of Food Science
Keywords: Composite enzymatic hydrolysis Ultrasonic Polypeptide Walnut pulp Antioxidant activity
CLC: TS255.6
Type: Master's thesis
Year: 2011
Downloads: 8
Quote: 0
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Abstract


15% protein is contained in walnut kernel, but the fat is up to 70%. Its special nutritional structure is an important bottleneck to develop walnut milk beverage; Glutenin is the main components of walnut protein, but it contains lots of hydrophobic amino acids whose solubility is bad, so application of walnut is seriously limited in food industry.In this experiment, on the basis of the mechanical fragmentation, walnut as the main raw material is made into walnut pulp which is processed by pectinase and cellulase compound enzyme, while ultrasonic technology is applied to improve oil yield, at last part of oil is obtained by centrifugation; Then compoud protease is used to obtain standard walnut pulp which is rich in polypeptide and whose protein and fat content reaches 2.5%. Hydrolysis is controlled correctly. Studies have shown that walnut polypeptide is more easily digested and absorbed than protein or amino acid. Walnut polypeptide also has antioxidant activity and so on. This study further explores the antioxidant activity of peptides in the walnut pulp. Finally, the walnut pulp is developed into walnut peptide milk with high antioxidant activity.1. After properly baking and grinding, Peeled walnut is made into walnut pulp which is processed by pectinase and cellulase compound enzyme, while ultrasonic technology is applied to obtain nutritional walnut oil. The enzymatic hydrolysis conditions were optimized. The results showed that the solid-liquid ration was 1:0.35, the compound ratio of pectinase and cellulase was 1:0.1, namely addition amount of pectinase was 450 U/g and cellulase was 45 U/g, the enzymatic time was 90 min at 55℃. After centrifuging for 20 min at 5000 r/min, the extraction rate of oil was 47.66%. On the condtion of ultrasonic power 80 W and ultrasonic time 20 min, the oil yield reached 52.62%.2. Multi-enzyme system with endoprotease and circumscribed peptidase can basically eliminate bitterness. According to polypeptide concentration, the proper protease is selected to form multi-enzyme system. The enzymatic hydrolysis conditions were optimized. The optimum conditions were triple-enzyme composite hydrophobic:(The ratio of alkaline protease and papain was 1:1, E/S=5000 U/g, flavourzyme was 1000u/mL), the temperature was 55℃, the time was 180 min. The polypeptide of walnut pulp is up to 20.89 mg/ml.3. Compared with ascorbic acid Vc, walnut polypeptide was studied in vitro antioxidant activity of different systems. The results showed that:with walnut polypeptide concentration increased, the reducing power, DPPH·, hydroxyl radical (·OH), superoxide anion (O2·-) scavenging and total antioxidant capacity also increased. In the experimental concentration range, it had a good dose-effect relationship. Determination of in vitro antioxidant activity of all systems, the removal effects of walnut peptide were not as good as Vc, but still showed strong antioxidant activity.4. Walnut pulp as raw materials was developed into nutritional peptide milk beverage. Different excipients were studied on the impact of the flavor and appearance. The ingredients of beverage contain:cane sugar 6%, mixed acid 0.1%, (3-CD 0.6%and composite stabilizer 0.2%. Walnut milk beverage rich in peptide was delicious and the bitterness was not obvious.The preparation of highly active standardized walnut pulp completely solves the problems with excessive walnut oil, which could be provided as raw materials based for other deep-processed products such as walnut powder, walnut milk, walnut yogurt. The study has important theoretical and applied significance on the promotion of comprehensive development and utilization of walnut. The study provides a new way for the processing of walnut.

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