Enzymolysis reaction kinetics and thermodynamics of rapeseed protein with sequential dual‐frequency ultrasound pretreatment

We evaluated the effect of sequential dual‐frequency ultrasound (SDFU) pretreatments on rapeseed protein enzymolysis, using alcalase as a model enzyme. Hydrolysed protein concentrations, enzymolysis kinetics and thermodynamic parameters were investigated. The results showed that the hydrolysed rapeseed protein concentration following SDFU pretreatments was higher compared to that of the control for up to 75 min of enzymolysis at various substrate concentrations of 5–25 g L^?1; both control and SDFU pretreatment groups showed first‐order reaction kinetics. Compared to the control, the Michaelis–Menten constant (K_M) value decreased remarkably by 17.61%, while an increase in the binding frequency between enzyme and substrate (K_A) by 10.47% was observed. The thermodynamic parameters, enthalpy, entropy and activation energy were reduced in the SDFU pretreatment group compared to the control by 31.78%, 18.0% and 29.56%, respectively. SDFU pretreatment showed little effect on Gibbs free energy at the various temperatures studied.     

Lipid and protein stability of partially defatted walnut flour (Juglans regia L.) during storage

Partially defatted walnut flour (WF) was stored (25 °C, 800 Lux) for an 8‐month period and evaluated monthly in some protein properties and oil oxidative parameters. Transparent plastic‐laminated (WFPL) and plastic‐laminated, aluminium‐coated (WFAC) packages were used. During the first 3 months, samples were more susceptible to endogenous hydrolysis; an increase in soluble peptide concentration was determined for both WFAC and WFPL. Minor changes between WFAC and WFPL were observed in protein electrophoretic patterns along storage period, but no differences were determined in total protein solubility. However, a progressive reduction in water‐holding capacity (47% from time 0 to month 8) was observed for WFPL. A major effect of packaging material was found on lipid‐quality parameters. Packaging materials’ barrier to light effectively protect WF against polyunsaturated FA degradation and oil oxidation. Lipids from WF stored in plastic‐laminated packages showed decreasing double‐bond index values (from 1.71 at initial time, to 1.45 after 6 months of storage) and increasing oxidation rates along storage test. Aluminium‐coated packages can be used to keep quality of WF for 8 months at room temperature.     

Effects of high hydrostatic pressure on physicochemical and functional properties of walnut (Juglans regia L.) protein isolate

BACKGROUND: Walnut (Juglans regia L.) is a good source of protein that has potential application in new product formation and fortification. The main objectives of this study were to investigate the effects of high hydrostatic pressure (HHP) treatment (300–600 MPa 20 min) on physicochemical and functional properties of walnut protein isolate (WPI) using various analytical techniques at room temperature. RESULTS: The results showed significant modification of solubility, free sulfhydryl content and surface hydrophobicity with increased levels of HHP treatment, indicating partial denaturation and aggregation of proteins. Differential scanning calorimetry and fluorescence spectrum analyses demonstrated that HHP treatment resulted in gradual unfolding of protein structure. Emulsifying activity index was significantly (P < 0.05) increased after HHP treatment at 400 MPa, but significantly decreased (P < 0.05) relative to the untreated WPI with further increase in pressure. HHP treatment at 300–600 MPa significantly decreased emulsion stability index. Additionally, HHP‐treated walnut proteins showed better foaming properties and in vitro digestibility. CONCLUSION: These results suggest that HHP treatment could be applied to modify the properties of walnut proteins by appropriate of pressure levels, which will help in using walnut protein as a potential food ingredient. © 2012 Society of Chemical Industry     

Walnut (Juglans regia L.): genetic resources,chemistry, by‐products

Walnut (Juglans regia L.) is the most widespread tree nut in the world. There is a great diversity of genotypes differing in forestry, productivity, physical and chemical nut traits. Some of them have been evaluated as promising and may serve as germplasm sources for breeding. The nutritional importance of the nut is related to the seed (kernel). It is a nutrient‐dense food mainly owing to its oil content (up to 740 g kg^?1 in some commercial varieties), which can be extracted easily by screw pressing and consumed without refining. Walnut oil composition is dominated largely by unsaturated fatty acids (mainly linoleic together with lesser amounts of oleic and linolenic acids). Minor components of walnut oil include tocopherols, phospholipids, sphingolipids, sterols, hydrocarbons and volatile compounds. Phenolic compounds, present at high levels in the seed coat but poorly extracted with the oil, have been extensively characterised and found to possess strong antioxidant properties. The oil extraction residue is rich in proteins (unusually high in arginine, glutamic and aspartic acids) and has been employed in the formulation of various functional food products. This review describes current scientific knowledge concerning walnut genetic resources and composition as well as by‐product obtainment and characteristics. Copyright © 2010 Society of Chemical Industry     

Walnuts (Juglans regia L): proximate composition,protein solubility,protein amino acid composition and protein in vitro digestibility

Walnuts contained 16.66% protein and 66.90% lipids on a dry weight basis. Non‐protein nitrogen values ranged from 6.24 to 8.45% of the total nitrogen when the trichloroacetic acid concentration was varied within the range 0.25–1.0 M . Albumin, globulin, prolamin and glutelin respectively accounted for 6.81, 17.57, 5.33 and 70.11% of the total walnut proteins. Walnut proteins were minimally soluble at pH 4.0. The majority of total walnut protein polypeptides had estimated molecular weights in the range 12 000–67 000. The Stokes radius of the major protein in walnuts (glutelin fraction) was 66.44 ± 1.39 Å. Lysine was the first limiting essential amino acid in total walnut proteins as well as in the globulin and glutelin fractions. Leucine and methionine plus cysteine were the second limiting essential amino acids respectively for the prolamin and albumin fractions. Hydrophobic and acidic amino acids dominated the amino acid composition in all protein fractions. Native and heat‐denatured walnut glutelins were easily hydrolysed by trypsin, chymotrypsin and pepsin in vitro. © 2000 Society of Chemical Industry     

The antioxidant activities and the xanthine oxidase inhibition effects of walnut (Juglans regia L.) fruit,stem and leaf

The antioxidant activities and xanthine oxidase inhibition effects of walnut fruit, stem and leaf were studied in this work. The total phenolic contents were in a descending sequence: shell extract > leaf extract > stem extract > defatted walnut kernel (DWK) extract > green husk extract (GHE). The sequence of total phenolic contents was in agreement with the sequence of antioxidant capacities evaluated by ferric reducing antioxidant power and oxygen radical absorbance capacity (ORAC) assays except for DWK extract. The walnut shell extract showed the highest phenolic content (14.81 gallic acid equivalent g/100 g dry extract) and the best antioxidant activity (the ORAC value was 3423.44 ± 142.52 μmol Trolox equivalents g^?1). All tested samples possessed xanthine oxidase inhibitory (XOI) effects, the inhibition percentages of which were >50% at 2 mg mL^?1 except for stem and DWK extracts. The contents of the major compound (hydrojuglone) in all extracts were in a descending order: GHE > walnut stem extract > walnut shell extract > walnut leaf extract > DWK extract.     

Production of a high‐protein meal and fermentable sugars from defatted soybean meal,a co‐product of the soybean oil industry

The goal of this research was to produce a high‐protein meal by treating defatted soybean meal, a by‐product of soybean oil production, with dilute acid. Treatments were a mild hydrolysis at 80 °C with sulphuric acid at concentrations ranging from 0.5% to 2.0% (w/v) and times varying from 1 to 16 h that were arranged according to a central composite rotatable experimental design. The end products were an enhanced‐protein meal and a carbohydrate concentrate of fermentable and nonfermentable sugars. The highest protein content rise, from 48% to 58%, was for treatments with concentrations of acid ranging between 1.2% and 1.7% and times between 1.0 and 2.6 h. The maximum yield of fermentable sugar was 21.0% d.b. at 2.0% H₂SO₄ and treatments of at least 6 h. The conditions that provide a highest protein and sugar contents were the treatments with concentrations of sulphuric acid ranging from 0.9 to 1.9% H₂SO₄ for 1–4 h.     

Antihyperuricemic activities of an ethanolic and aqueous extract of Walnut (Juglans regia L.) shell and a new aldehyde xanthine oxidase inhibitor

Hyperuricemia is a common metabolic disorder disease in human and is associated with increased xanthine oxidase (XOD) activity. This study was aimed to evaluate the antihyperuricemic activities of an ethanolic and aqueous extract of walnut (Juglans regia L.) shell in vivo and obtain active compounds with high xanthine oxidase inhibitory (XOI) activities and distinct chemical structures form allopurinol in vitro. Finally, the structure–XOI activity relationship of the active compound was further discussed based on the molecular docking. The in vivo antihyperuricemic study indicated that the walnut shell extract (WSE) could decrease the serum uric acid levels significantly (20‐days treatment, P < 0.05; 30‐days treatment, P < 0.01). And a new aldehyde XOD inhibitor with high XOI activity was obtained through XOI activity‐guided purification in vitro. The studies of structure–XOI activity relationship and molecular docking indicated that the synergy of aldehyde group, double bond and hydroxyl group at C‐4 in p‐coumaric aldehyde was the critical contributor for its high XOI activity.     

Viscozyme L预处理花生粕提取花生浓缩蛋白的研究

为了优化复合植物水解酶(ViscozymeL)预处理花生粕结合乙醇洗涤法制备花生浓缩蛋白的工艺条件,以花生粕为原料,采用单因素实验和响应面实验设计方法,研究花生浓缩蛋白制备工艺条件对蛋白质量百分含量和提取率的影响。结果表明,ViscozymeL预处理花生粕结合乙醇洗涤法制备花生浓缩蛋白的最优工艺参数为:酶添加量6.1 FBG/g、pH值4.2、酶解温度43℃、酶解时间4.5 h,在最佳工艺条件下,蛋白的质量百分含量和提取率验证实验值分别为73.21%±0.59%和85.23%±0.67%,两者与模型预测值的差异均小于1%。为进一步开发利用花生粕提供了一种新途径。     

长白山区核桃青皮多糖分离纯化、鉴定及抗氧化活性分析

对核桃青皮多糖（polysaccharide of walnut green husks,JPs）进行分离纯化,并对得到的多糖进行单糖组成及体外抗氧化活性分析。利用超声波辅助提取JPs,经醇沉、除蛋白、透析等一系列处理后,先后利用DEAE-Sepharose和Sephadex?G-100柱色谱分离纯化JPs得到了两种均一多糖（JPs-1-1和JPs-2-1）;利用高效凝胶渗透色谱法测定两种均一多糖的分子质量分别为5.45×104、5.22×104?u;利用PMP-柱前衍生高效液相色谱法测定了两种均一多糖的单糖组成,均是由鼠李糖（Rha）、葡萄糖醛酸（GlcA）、半乳糖（Gal）、葡萄糖（Glc）、半乳糖醛酸（GalA）、木糖（Xyl）及阿拉伯糖（Ara）以不同的物质的量比组成。总抗氧化能力实验、1,1-二苯基-2-苦味基肼自由基和羟自由基清除实验结果表明JPs及分离纯化得到的两种均一多糖均具有较好的抗氧化活性,而且抗氧化活性的能力与样品的质量浓度呈正相关。     

Antioxidant and nitric oxide inhibitory activities of tilapia (Oreochromis niloticus) protein hydrolysate: effect of ultrasonic pretreatment and ultrasonic‐assisted enzymatic hydrolysis

Ultrasound was incorporated to processing of fish protein hydrolysate to facilitate homogenate pretreatment and enzymatic hydrolysis of tilapia (Oreochromis niloticus) muscle protein. Their effects on Flavourzyme hydrolysis and biological activities of the tilapia hydrolysate were examined. The ultrasound‐assisted hydrolysis caused reduction in degree of hydrolysis ranging from 23% to 35% relative to that of the conventional process. The 70 W ultrasound‐assisted hydrolysis process increased DPPH radical‐scavenging activity and reducing power of tilapia hydrolysate prepared from the non‐pretreatment homogenate by 33% and 45%, respectively. All hydrolysates have no cytotoxicity on RAW264.7 cell lines at the maximum concentration of 20 mg protein mL^?1. The 70 W ultrasound pretreatment at 30 and 45 min combined with conventional hydrolysis is the suitable condition for producing tilapia hydrolysate with nitric oxide inhibitory and antioxidative activities on RAW264.7 cell lines, respectively. As a result, ultrasound could be applied to enzymatic protein hydrolysis either as pretreatment or during the hydrolysis.     

Effects of nano‐clay type and content on the physical properties of sesame seed meal protein composite films

Sesame seed meal protein (SSMP)/nano‐clay composite films were prepared, and the physical properties of the films were determined. The SSMP film was prepared with 5 g of SSMP and 2 g of glycerol in 100 mL of film‐forming solution, and the tensile strength (TS), elongation (E) and water vapour permeability (WVP) of the SSMP film were 2.51 MP, 21.84% and 3.23 × 10^?9 g m m^?2s^?1 Pa^?1, respectively. Two types of nano‐clays were incorporated to enhance the physical properties of the SSMP film. The TSs of the SSMP film with 5% Cloisite Na⁺ and 7% Cloisite 10A were 6.32 and 5.76 MPa, respectively, and the WVPs of the SSMP nanocomposite films were 2.04 × 10^?9 g m m^?2s^?1 Pa^?1 compared with the SSMP film without nano‐clay, which was 3.23 × 10^?9 g m m^?2s^?1 Pa^?1. Therefore, these results indicate that the SSMP nanocomposite film can be applied in food packaging.     

沙棘籽粕蛋白的碱酶两步法提取工艺及功能性研究

以沙棘籽粕为原料,采用碱提酸沉法提取沙棘籽粕蛋白,得到最佳提取工艺参数为:pH10、料液比1:12、温度60℃、时间60min。后用碱性蛋白酶对碱提残渣中的蛋白进行水解,最适提取条件为:pH8.5、碱性蛋白酶加酶量240U/g、料液比1:10、60℃、60min。通过碱提、酶法两步提取后,总提取率为67.24%。并对其乳化活力和乳化稳定性等功能性质进行了研究,表明性质受pH、温度、盐离子浓度等环境因素影响大,在等电点pH5.0附近时乳化活力和乳化稳定性的数据最低。      

Comparison of enzyme‐assisted and ultrasound‐assisted extraction of vitamin C and phenolic compounds from acerola (Malpighia emarginata DC.) fruit

This article describes a comparative study of enzyme and ultrasound techniques for the simultaneous extraction of vitamin C and phenolic compounds from acerola fruit. Ultrasound‐assisted extraction (UAE) took only 6 min to achieve the highest level of vitamin C and phenolic compounds as well as antioxidant activity of acerola juice, while enzyme‐assisted extraction (EAE) took up to 120 min to obtain the maximal values. On the basis of kinetic model of second‐order extraction, the extraction rate constant of vitamin C and phenolics in UAE increased approximately 3.1 and 2.7 times, respectively, in comparison with that in EAE. In addition, the maximal level of vitamin C, phenolics and the antioxidant activity evaluated by 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH), and 2,2′‐azinobis‐(3‐ethylbenzothiazoline‐6‐sulphonic acid) (ABTS) methods in UAE was 4.6%, 3.5%, 4.6% and 3.3%, respectively, higher than those in EAE. Obviously, UAE is a useful method for the extraction of antioxidants from plant materials.