Effect of Solid Content and Lipid Content of Whey Protein Isolate-Beeswax Edible Coatings on Color Change of Fresh-cut Apples

ABSTRACT: Edible coatings from whey protein isolate (WPI)-beeswax (BW) were made with various total solid (8%, 12%, 16%, 20%) and BW content (0%, 20%, 40%, 60%, dry bases). Apple pieces were coated with the emulsion coatings; weight loss and color (CIE L*, a*, b* , and browning index [BI]) were measured during storage. Results show that coated apples had higher L* and presented lower BI than uncoated apples, indicating that whey proteins exert an antibrowning effect. The BI decreased as the solid content of the coating emulsions increased. Increasing BW content decreased enzymatic browning. Coating application did not reduce weight loss in fresh-cut apples, probably due to the product's high relative humidity.     

Coating of Peanuts with Edible Whey Protein Film Containing α‐Tocopherol and Ascorbyl Palmitate

ABSTRACT: Physical properties of whey protein isolate (WPI) coating solution incorporating ascorbic palmitate (AP) and α‐tocopherol (tocopherol) were characterized, and the antioxidant activity of dried WPI coatings against lipid oxidation in roasted peanuts were investigated. The AP and tocopherol were mixed into a 10% (w/w) WPI solution containing 6.7% glycerol. Process 1 (P1) blended an AP and tocopherol mixture directly into the WPI solution using a high‐speed homogenizer. Process 2 (P2) used ethanol as a solvent for dissolving AP and tocopherol into the WPI solution. The viscosity and turbidity of the WPI coating solution showed the Newtonian fluid behavior, and 0.25% of critical concentration of AP in WPI solution rheology. After peanuts were coated with WPI solutions, color changes of peanuts were measured during 16 wk of storage at 25 °C, and the oxidation of peanuts was determined by hexanal analysis using solid‐phase micro‐extraction samplers and GC‐MS. Regardless of the presence of antioxidants in the coating layer, the formation of hexanal from the oxidation of peanut lipids was reduced by WPI coatings, which indicates WPI coatings protected the peanuts from oxygen permeation and oxidation. However, the incorporation of antioxidants in the WPI coating layer did not show a significant difference in hexanal production from that of WPI coating treatment without incorporation of antioxidants.     

Physicochemical Property and Oxidative Stability of Whey Protein Concentrate Multiple Nanoemulsion Containing Fish Oil

The objectives of this research were to produce whey protein concentrate (WPC) multiple nanoemulsion (MNE) and to study how whey protein concentration level and antioxidant type affected the physicochemical properties and oxidative stability of fish oil in MNE. The morphological and physicochemical characteristics of MNE were investigated by using transmission electron microscopy and particle size analyzer, respectively. The oxidative stability of fish oil in MNEs was assessed by measuring peroxide value (PV), p‐anisidine value, and volatile compounds. The spherical forms of emulsions with size ranging from 190 to 210 nm were observed indicating the successful production of MNE. Compared with free fish oil, fish oil in MNE exhibited lower PV, p‐anisidine value, and formation of maker of oxidation of fish oil indicating the oxidative stability of fish oil in MNE was enhanced. PV, p‐anisidine value, and makers of oxidation of fish oil were decreased with increased WPC concentration level. The combined use of Vitamin C and E in MNE resulted in a reduction in PV and p‐anisidine value, and development of maker of oxidation. In conclusion, WPC concentration level and antioxidant type are key factors affecting the droplet size of MNE and oxidative stability of fish oil.     

涂膜处理对鲜切山药褐变及抗氧化性的影响

为保持鲜切山药的色泽及抗氧化性,延长其货架期,研究壳聚糖、卡拉胶、海藻酸钠及复合涂膜剂对鲜切山药涂膜处理后,在5℃贮藏期间褐变及抗氧化性的影响。结果表明:壳聚糖1.57%+卡拉胶0.9%+海藻酸钠1.55%涂膜后,鲜切山药储存期间,可明显降低山药的褐变程度及抑制PPO的比活力,防止贮藏后期酚类物质的氧化,提高鲜切山药的整体抗氧化能力。     

Browning Inhibition and Textural Changes of Pre-Peeled Potatoes Caused by Anaerobic Conditions

Sulphite treatment is often used for inhibition of enzymatic browning of pre-peeled potatoes. Introduction of CO₂ or N₂ gases in the immersion water was investigated as an alternative to sulphite. The samples were stored at 4 °C. Daily introduction of the gases reduced the O₂ content from approx. 8.8 mg/L (measured at 20 °C) to 0.2-1.9 mg/L during the immersion period. The CO₂ treatment inhibited the browning completely and N₂ treatment did not. It is assumed that this is due to the lower pH in the CO₂ water. When CO₂ was added only one time at the start of the experiment, it also inhibited discoloration, but the immersion water developed a weak brown colour. Both the CO₂ and the N₂ treatment induced hardening in the outer potato tuber tissue after cooking after 4-7 d of storage, as did Na₂SO₃ solutions.     

Physical properties of whey protein coating solutions and films containing antioxidants

ABSTRACT:  Antioxidants (ascorbyl palmitate and α-tocopherol) were incorporated into 10% (w/w) whey protein isolate (WPI) coating solution containing 6.67% (w/w) glycerol (WPI:glycerol = 6:4). Before incorporation, the antioxidants were mixed using either powder blending (Process 1) or ethanol solvent-mixing (Process 2). After the antioxidant mixtures were incorporated into heat-denatured WPI solution, viscosity and turbidity of the WPI solutions were determined. The WPI solutions were dried on a flat surface to produce WPI films. The WPI films were examined to determine transparency and oxygen-barrier properties (permeability, diffusivity, and solubility). WPI solution containing antioxidants produced by Process 1 and Process 2 did not show any difference in viscosity and turbidity, but viscosity was greater for the WPI solution with rather than without antioxidants. WPI films produced by Process 2 were more transparent than the films produced by Process 1. Oxygen permeability of Process 1 film was lower than Process 2 film. However, both the diffusivity and solubility of oxygen were statistically the same in Process 1 and Process 2 films. Both control WPI films and antioxidant-containing WPI films had very low oxygen solubility, comparable to polyethylene terephthalate films. Permeability of antioxidant-incorporated films was not enhanced compared to control WPI films.     

南方山葡萄酒的氧化褐变动力学研究

为深入了解红葡萄酒的氧化机制,利用加速氧化的方法,通过分析2种南方山葡萄酒氧化褐变过程中,褐变程度、红色色调、游离SO2、氧化还原电位以及氧化前、后主要理化指标的变化,研究南方山葡萄酒的氧化褐变动力学、主要影响因素及对葡萄酒品质的影响。试验结果表明:南方山葡萄酒的氧化褐变动力学符合0级动力学模型方程,桂葡1号葡萄酒耐氧化能力高于刺葡萄酒,然而其红色色调的保持力要低于刺葡萄酒。在加速氧化过程中,葡萄酒的游离SO2快速下降,氧化-还原电位加速上升,且二者呈显著的负相关关系。加速氧化30 d后,2种葡萄酒的总酸、挥发酸升高,其pH值和主要的抗氧化物质(原花青素、游离花色苷、总酚)均显著下降。     

Color Stability of Edible Coatings During Prolonged Storage

ABSTRACT: The yellowing rates of edible coatings were determined at 23, 40, and 55 °C at 75% relative humidity (RH). Whey protein isolate (WPI) coatings had lower yellowing rates than whey protein concentrate (WPC) and the same rates as shellac coatings. Hydroxypropyl methylcellulose (HPMC) coatings had the lowest yellowing rates. Zein coatings became less yellow during storage; however, their color was still pronounced. Activation energies and Q₁₀ values for the yellowing of whey protein coatings were similar to those previously reported for the browning of whey powder. The results indicate that WPI coatings can be used in place of shellac coatings when low-color development is desired. WPC coatings can be used to tailor color development of a food.     

可食性复合涂膜保鲜剂对延长鲜切苹果货架期的研究

本文主要研究了可食性涂膜剂与抗褐变剂复配后对鲜切苹果的保鲜效果。研究表明:25℃条件下,苹果切块经卡拉胶(0.5%)涂膜剂和乳清浓缩蛋白WPC(5%)涂膜剂处理后,其呼吸强度可分别降低5%和20%。在可食性涂膜剂中添加不同的抗褐变剂对苹果切块有良好的护色效果,添加1%CaCl2可增加产品的硬度,同时这些复合保鲜剂可提高苹果切块的感官指标和抑制微生物繁殖,而5%WPC涂膜液+1%CaCl2+1%抗坏血酸复合液浸泡苹果切块,3℃条件下贮藏2w后保鲜效果最佳。     

Invited review: Whey proteins as antioxidants and promoters of cellular antioxidant pathways

Oxidative stress contributes to cell injury and aggravates several chronic diseases. Dietary antioxidants help the body to fight against free radicals and, therefore, avoid or reduce oxidative stress. Recently, proteins from milk whey liquid have been described as antioxidants. This review summarizes the evidence that whey products exhibit radical scavenging activity and reducing power. It examines the processing and treatment attempts to increase the antioxidant bioactivity and identifies 1 enzyme, subtilisin, which consistently produces the most potent whey fractions. The review compares whey from different milk sources and puts whey proteins in the context of other known food antioxidants. However, for efficacy, the antioxidant activity of whey proteins must not only survive processing, but also upper gut transit and arrival in the bloodstream, if whey products are to promote antioxidant levels in target organs. Studies reveal that direct cell exposure to whey samples increases intracellular antioxidants such as glutathione. However, the physiological relevance of these in vitro assays is questionable, and evidence is conflicting from dietary intervention trials, with both rats and humans, that whey products can boost cellular antioxidant biomarkers.     

Milk proteins for edible films and coatings

Due to the recent increase in ecological consciousness, research has turned toward finding edible materials. Viable edible films and coatings have been produced using milk proteins. These films and coatings may retard moisture loss, are good oxygen barriers, show good tensile strength and moderate elongation, are flexible, and generally have no flavor or taste. Incorporation of lipids in protein films, either in an emulsion or as a coating, improve their properties as barriers to moisture vapor. Interactions between chemical, structural properties, as well as film-forming conditions and functional properties of edible milk films are elucidated. Some potential uses of milk protein packaging, which are hinged on film properties, are described with examples.     

Comparison of the Emulsifying Properties of Fish Gelatin and Commercial Milk Proteins

ABSTRACT: We have compared the flocculation, coalescence, and creaming properties of oil-in-water emulsions prepared with fish gelatin as sole emulsifying agent with those of emulsions prepared with sodium caseinate and whey protein. Two milk protein samples were selected from 9 commercial protein samples screened in a preliminary study. Emulsions of 20 vol% n -tetradecane or triglyceride oil were made at pH 6.8 and at different protein/oil ratios. Changes in droplet-size distribution were determined after storage and centrifugation and after treatment with excess surfactant. We have demonstrated the superior emulsifying properties of sodium caseinate, the susceptibility of whey protein emulsions to increasing flocculation on storage, and the coalescence of gelatin emulsions following centrifugation.     

Listeria monocytogenes Inhibition by Whey Protein Films and Coatings Incorporating the Lactoperoxidase System

Antimicrobial effects of whey protein isolate (WPI) films and coatings incorporating the lactoperoxidase system (LPOS) against Listeria monocytogenes were studied by turbidity, plate counting, disc‐covering, and disc‐surface‐spreading tests using various growth media. Survival of L. monocytogenes applied to smoked salmon before or after the coating was monitored immediately after application and during storage at 4 °C and 10 °C for up to 35 d. Tensile properties (elastic modulus [EM], tensile strength [TS], elongation [E]), oxygen permeability (OP), and color (Hunter L, a, b) of WPI films, with and without LPOS, were also compared. LPOS inhibited L. monocytogenes in broth and on agar media. WPI films incorporating 29 mg of LPOS per gram of film (dry basis) inhibited 4.2 log colony‐forming units (CFU)/cm² of L. monocytogenes inoculated on agar media. WPI coatings prepared with LPOS at 0.7% (w/w) in a coating solution (40 mg LPOS/g coating [dry basis]) initially reduced >3 and 1 log CFU/g of L. monocytogenes and total aerobic microorganisms in smoked salmon, respectively. The WPI coatings incorporating LPOS prevented the growth of L. monocytogenes in smoked salmon at 4 °C and 10 °C for 35 d and 14 d, respectively. The tensile properties, oxygen permeability, and color of WPI films were not significantly changed by incorporation of LPOS (P >0.05).     

不同模式体系美拉德反应程度及抗氧化活性比较

以葡萄糖、果糖、蛋氨酸、甘氨酸、精氨酸和大豆分离蛋白为美拉德反应原料,研究加热时间和混合比例对褐变程度的影响,并对褐变程度最强的产物进行抗氧化活性检测。结果表明：葡萄糖、果糖分别与甘氨酸按物质的量之比2:1混合(pH9.0),并于100℃恒温水浴锅中加热180min时褐变程度最强。葡萄糖-甘氨酸与果糖-甘氨酸模式体系的美拉德反应物都具有一定的抗氧化能力。在相同体积分数条件下,果糖-甘氨酸模式体系的美拉德反应物的还原能力和抗氧化值均要强于葡萄糖-甘氨酸模式体系的美拉德反应物。葡萄糖-甘氨酸模式体系的美拉德反应物对 ·OH和O2 ·的抑制率最高分别达50.65%和45.42%,而果糖-甘氨酸模式体系的美拉德反应物对 ·OH和O2 ·的抑制率最高则分别达57.55%和28.54%。     

Efficacy of Sardinelle Protein Hydrolysate to Alleviate Ethanol-Induced Oxidative Stress in the Heart of Adult Rats

The present study was undertaken to examine the protective effects of sardinelle proteins hydrolysate (SPH) obtained from heads and viscera against ethanol toxicity in the heart of adult rats. Twenty-four male rats of Wistar strain, weighing at the beginning of the experiment 250 to 300 g, were used in this study. They were divided into 4 groups: group (C) served as controls, group (Eth) received 30% ethanol solution at 3 g/kg body weight, group (SPH) received only 7.27 mg of SPH/kg body weight, and group (Eth-SPH) received ethanol and sardinelle proteins hydrolysate simultaneously. All treatments were made by gavage during 15 d. Treatment with ethanol revealed a significant elevation of malondialdehyde and protein carbonyl levels in the heart and of aspartate transaminase and alanine transaminase activities in plasma. Nitric oxide levels and the activities of antioxidant enzymes such as superoxide dismutase, catalase, and glutathione peroxidase decreased. Nonenzymatic antioxidant such as reduced glutathione did not significantly change and ascorbic acid was decreased. SPH intake concomitantly with ethanol restored these parameters to near control values. These modifications confirmed histopathological aspects of the heart. The results revealed that SPH could provide protection of the myocardium against ethanol-induced oxidative damages in rats. This may be due to the high antioxidant potential of SPH.     

竹叶抗氧化物/酪蛋白酸钠/乳清分离蛋白可食膜的制备和性能分析

为开发出一种具有良好性能的可食包装材料,本实验以乳清分离蛋白为成膜基质,添加竹叶抗氧化物和酪蛋白酸钠,制备竹叶抗氧化物/酪蛋白酸钠/乳清分离蛋白复合可食膜（antioxidant of bamboo leaves/sodium caseinate/whey protein isolate composite film,ASWF）,分析比较成膜材料质量比、pH值、甘油质量浓度对ASWF断裂拉伸强度、断裂伸长率、水蒸气透过量和透光率等物理性能的影响。结果表明,成膜材料竹叶抗氧化物、酪蛋白酸钠和乳清分离蛋白质量比为1∶1∶10、pH值为8～9、甘油质量浓度为0.04 g/mL时,ASWF断裂拉伸强度和断裂伸长率分别达18.4 MPa和32.8%,水蒸气透过量为10.86 g/（m2·d）,透光率为90.2%,具备良好的物理性能。傅里叶变换红外光谱扫描分析结果表明成膜材料间具有良好的相容性。扫描电子显微镜观察结果显示ASWF表面平整光滑,横截面规则、均匀。制备的可食膜对实际试样（鱿鱼干）表现出良好的微生物抑制作用和抗氧化作用。该研究为可食膜的研制提供参考。     

大豆分离蛋白-脂质涂层对冷却牛肉品质的影响

研究脂质(硬脂酸、棕榈酸、巴西棕榈蜡和三乙酸甘油脂)与大豆分离蛋白制成的可食性涂层对冷却牛肉品质的影响。考察冷却牛肉在4℃下贮藏108h过程中失重率、颜色、pH值、硫代巴比妥酸值和感官特性的变化。结果表明冷却牛肉在4℃贮藏时的货架期小于108h,而且在4℃贮藏84h后,不同大豆分离蛋白-脂质涂层的优点不同。其中,三乙酸甘油酯蛋白涂层不仅延缓冷却牛肉的氧化,而且有效维持其感官特性,对维持冷却牛肉品质和延长期货架期效果最佳。     

短波紫外线控制鲜切苹果褐变与其活性氧代谢的相关性

为研究短波紫外线（ultraviolet-C,UV-C）处理对鲜切苹果褐变控制与活性氧（reactive oxygen species,ROS）代谢的相关性,分析贮藏过程中UV-C处理后鲜切苹果的ROS水平、抗氧化相关酶活力、抗氧化物质（VC）含量以及非酶抗氧化能力的变化。结果表明：UV-C处理能够有效抑制鲜切苹果的褐变,降低超氧阴离子自由基产生速率和H2O2、丙二醛（malondialdehyde,MDA）含量;同时,UV-C处理能够有效提高抗氧化相关酶（超氧化物歧化酶、过氧化氢酶、抗坏血酸过氧化酶和谷胱甘肽还原酶）活力以及VC含量,减缓鲜切苹果非酶抗氧化能力（1,1-二苯基-2-三硝基苯肼自由基、2,2’-联氮-双(3-乙基苯并噻唑-6-磺酸)阳离子自由基清除能力和还原能力）在贮藏过程中的下降;相关性分析与主成分分析结果显示,鲜切苹果褐变程度与ROS水平和MDA含量呈显著正相关（P＜0.05）,与抗氧化酶活力和非酶抗氧化能力呈显著（P＜0.05）或极显著（P＜0.01）负相关,且UV-C处理组鲜切苹果的ROS代谢能力高于对照组。因此,推测UV-C处理可能通过调节鲜切苹果的ROS代谢进而控制其贮藏过程中的褐变。     

Edible Coatings on Frozen King Salmon: Effect of Whey Protein Isolate and Acetylated Monoglycerides on Moisture Loss and Lipid Oxidation

Whey protein isolate (WPI) and acetylated monoglyceride (AMG) coatings were evaluated for effectiveness against moisture loss and lipid oxidation of frozen King salmon. A model gel material was also used to screen coatings for effectiveness against moisture loss. Coatings of low-melting-point AMG used alone or after applying WPI solution or WPI powder were effective in reducing the rate of moisture loss by 42–65% during the first 3 wk of storage. Onset of lipid oxidation was delayed and peak peroxide values were reduced in samples coated with WPI solution/antioxidant overspray or those containing low-melting-point AMGs. No differences in effectiveness were found among the coating treatments.