Effectiveness of Cross-Flow Microfiltration for Removal of Microorganisms Associated with Unpasteurized Liquid Egg White from Process Plant

ABSTRACT:  Thermal preservation is used by the egg industry to ensure the microbiological safety of liquid egg white (LEW); however, it does not eliminate all microorganisms and impairs some of the delicate functional properties of LEW. In this study, a pilot-scale cross-flow microfiltration (MF) process was designed to remove the natural microflora present in commercial LEW, obtained from a local egg-breaking plant, while maintaining the nutritional and functional properties of the LEW. LEW, containing approximately 10^{6 ± 1.7} colony forming units (CFU) per milliliter of total aerobic bacteria, was microfiltered using a ceramic membrane with a nominal pore size of 1.4 μm, at a cross-flow velocity of 6 m/s. To facilitate MF, LEW was screened, homogenized, and then diluted (1 : 2, w/w) with distilled water containing 0.5% sodium chloride. Homogenized LEW was found to have a threefold lower viscosity than unhomogenized LEW. Influence of MF temperature (25 and 40 °C) and pH (6 and 9) on permeate flux, transmission of egg white nutrients across the membrane, and microbial removal efficiency were evaluated. The pH had a significantly greater influence on permeate flux than temperature. Permeate flux increased by almost 148% when pH of LEW was adjusted from pH 9 to pH 6 at 40 °C. Influence of temperature on permeate flux, at a constant pH, however, was found to be inconclusive. Microbial removal efficiency was at least 5 log₁₀ CFU/mL. Total protein and SDS-PAGE analysis indicated that this MF process did not alter the protein composition of the permeate, compared to that of the feed LEW, and that the foaming properties of LEW were retained in the postfiltered samples.     

响应面试验优化桑葚汁复合酶解制备工艺及微滤技术对其品质的影响

以新鲜成熟桑葚果实为原料,桑葚出汁率为指标,通过单因素试验及响应面试验,确定果胶酶和纤维素酶酶解制备桑葚汁的最佳工艺参数,并进一步考察非热力杀菌微滤技术对桑葚汁杀菌、澄清、褐变抑制效果以及理化指标的影响。研究结果表明,适于实际生产的最佳酶解工艺为：果胶酶添加量0.42%、纤维素酶添加量1.84%、酶解时间101.26 min、酶解温度50 ℃、酶解pH 3.5～4.0（桑葚汁自然pH值）。在此条件下,桑葚出汁率为86.37%,与理论值88.10%接近。实验表明微滤技术对桑葚汁不仅有很好的抑菌效果,且对桑葚汁的褐变具有一定的抑制作用。     

电渗析脱盐对咸鸭蛋蛋清理化性质的影响

目的：为评估电渗析脱盐是否对鸭蛋清的功能性质和营养性有影响,研究经电渗析脱盐后鸭蛋清的部分理化性质变化。结果：脱盐后鸭蛋清的凝胶硬度在蛋白质量浓度较低时(5～8g/100mL)与鲜鸭蛋清相比无显著差异;当蛋白质量浓度为3～9g/100mL时,脱盐鸭蛋清的乳化活性及起泡性较咸鸭蛋清均有所提高,与鲜鸭蛋清相比,两者乳化活性相当,但其起泡性优于鲜鸭蛋清;SDS-PAGE、DSC及氨基酸分析表明,咸鸭蛋清脱盐前后蛋白质相对分子质量无明显变化;脱盐后的鸭蛋清与鲜鸭蛋清的氨基酸组成、热变性温度及颜色均十分接近。结论：经电渗析脱盐处理,鸭蛋清的理化性质影响不大,可作为良好的食品原辅料。     

鸡蛋清中三种主要蛋白质的连续化提取分离研究

对鸡蛋清进行微滤、超滤浓缩后,加入60%的饱和硫酸铵盐析,得到了卵白蛋白粗品;上清液用Q-sepharoseF.F.离子交换层析,分离得到溶菌酶和卵铁传递蛋白,从而实现了蛋清中三种蛋白质的连续化提取。     

Removal of Salmonella Enteritidis from commercial unpasteurized liquid egg white using pilot scale cross flow tangential microfiltration

Effectiveness of a cross flow microfiltration (MF) process for removal of a cocktail of Salmonella enterica serovar Enteritidis species from commercial unpasteurized liquid egg white (LEW) from a local egg breaking plant, while maintaining its functional properties was evaluated. To facilitate MF, LEW was wedge screened, homogenized and then diluted (1:2 w/w) with distilled water containing 0.5% sodium chloride. Diluted unpasteurized LEW was inoculated with five strains of S. Enteritidis (ATCC 4931, ATCC BAA-708, ATCC 49215, ATCC 49218, and ATCC BAA-1045) to a level of approximately 10⁷ CFU/mL of LEW and microfiltered using a ceramic membrane. Process parameters influencing egg white functional properties and pathogen removal efficiency were evaluated. Average permeates flux increased by almost 126% when pH of LEW was adjusted from pH 8 to pH 7 at 25 °C. Microbial removal efficiency was at least, on average, 6.8 Log₁₀ CFU/mL (limit of detection ≤ 0.5 Log₁₀ CFU/mL). Functional property analysis indicated that the MF process did not alter the foaming power of LEW.     

Technological evaluation of dried egg white prepared by different techniques

Egg white was spray dried, using Egyptian fresh eggs, with and without glucose removal. Glucose depletion in egg white was carried out using bacteria yeast and enzyme. Foam capacity and stability of liquid egg white was also decreased by dehydration, except for egg white in which enzyme was used for glucose removal. Foam was more stable in samples desugared by yeast and least stable in enzyme treated egg white. Both pan drying and spray drying methods had the same effect on foam capacity and stability of egg white. The pH value of liquid egg white was found to decrease by removing glucose and to increase by dehydration. The specific volume data and organoleptic evaluation of angel food cakes in which dehydrated egg white, imported dried egg white and fresh egg white were used, showed that the best method to prepare dehydrated egg white is by using enzymatic treatment for glucose removal before dehydration.     

一株耐受蛋清蛋白的鸡蛋腐败菌S菌株的分离鉴定及其De novo测序分析

本实验采用传统微生物培养法从鸡蛋中分离出一株革兰氏阳性腐败菌S菌株,经形态学观察、生理生化分析及16S rDNA序列比对,对其进行了鉴定,并构建系统发育树。采用抑菌圈法及存活率试验探究该菌株对蛋清环境的耐受性,并基于Illumina HiSeq测序平台对该菌株的全基因组进行了De novo测序,获得基因组框架图。结果表明,该菌株生理生化反应特征与皮生球菌属相似,且16S rDNA序列与Dermacoccus abyssi(登录号AY894323)的同源性高达99%,鉴定为深渊皮生球菌(Dermacoccus abyssi)。该菌株在含有蛋清或溶菌酶的试管中能生长,在添加了蛋清或溶菌酶的孔径中没有抑菌圈产生。对蛋白编码基因的功能注释结果显示,细菌参与膜转运、离子结合、氨基酸和碳水化合物代谢及能量转换相关的基因丰富,推测其在鸡蛋中可能通过调节相关基因来耐受蛋清抑菌环境。该菌株对蛋清及溶菌酶的耐受性,为其在鸡蛋中的存活提供了有利条件。     

The Role of Wheat and Egg Constituents in the Formation of a Covalent and Non‐covalent Protein Network in Fresh and Cooked Egg Noodles

Noodles of constant protein content and flour‐to‐egg protein ratio were made with whole egg, egg white, or egg yolk. The optimal cooking time, water absorption, and cooking loss of salted whole egg noodles was respectively lower and higher than of egg white and egg yolk noodles. However, cooked whole egg noodles showed the best Kieffer‐rig extensibility. Differences in noodle properties were linked to protein network formation. Disulfide bonds in whole egg noodles developed faster and to a larger extent during cooking than in egg yolk noodles but slower and to a lower extent than in egg white noodles. The balance between the rate of protein cross‐linking and starch swelling determines cooked noodle properties. Ionic and hydrophobic protein interactions increase the optimum cooking time and total work in Kieffer‐rig extensibility testing of fresh noodles. Hydrogen bonds and covalent cross‐links are probably the main determinants of the extensibility of cooked noodles.     

复合涂膜剂对海南咸水鸭蛋的保鲜

采用羧甲基纤维素钠(CMC-Na)与纳米二氧化钛(nano-TiO₂)2种材料进行复合,通过研究复合膜的性能,找出较合适的二氧化钛含量,用于咸水鸭蛋的涂膜保鲜研究。结果表明羧甲基纤维素钠膜中添加适量纳米二氧化钛能增强其抗张强度,降低水蒸气透过率和溶胀性能,添加4%nano-TiO₂的复合膜的综合性能较好。以CMCNa/4%nano-TiO₂的溶液涂膜咸水鸭蛋,考察其对蛋贮藏期间失重率、蛋清pH、蛋黄指数、哈夫单位、菌落总数等新鲜度指标的影响,发现不经涂膜的空白组贮藏到21 d时,已不适宜消费者食用,而CMC-Na/nano-TiO₂涂膜组到42 d时,还在可食用范围内,不添加nano-TiO₂的CMC-Na涂膜组可以将鸭蛋保鲜至35 d。所以CMC-Na涂膜可以延长咸水鸭蛋的贮藏期,添加nano-TiO₂的涂膜组比未添加的效果更好。     

Membrane Processing Technology in the Food Industry: Food Processing,Wastewater Treatment,and Effects on Physical,Microbiological, Organoleptic,and Nutritional Properties of Foods

Membrane processing technology (MPT) is increasingly used nowadays in a wide range of applications (demineralization, desalination, stabilization, separation, deacidification, reduction of microbial load, purification, etc.) in food industries. The most frequently applied techniques are electrodialysis (ED), reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), and microfiltration (MF). Several membrane characteristics, such as pore size, flow properties, and the applied hydraulic pressure mainly determine membranes’ potential uses. In this review paper the basic membrane techniques, their potential applications in a large number of fields and products towards the food industry, the main advantages and disadvantages of these methods, fouling phenomena as well as their effects on the organoleptic, qualitative, and nutritional value of foods are synoptically described. Some representative examples of traditional and modern membrane applications both in tabular and figural form are also provided.     

Volatiles and Sensory Characteristics of Cooked Egg Yolk, White and Their Combinations

Headspace volatiles were produced by heating fresh egg yolk, white and different ratios of yolk to white. Volatiles of the same treatments produced during steam distillation extraction were identified, compared, and related to sensory characteristics of fresh scrambled eggs. Overall impression, sulfur, and sweet notes were sensory characteristics identified to distinguish between samples with varying yolkwhite ratios. Volatile concentrations of compounds in the headspace, and steam distillation/ solvent extracts were used to distinguish between scrambled eggs with different yolk:white ratios. The concentration of both egg yolk and white had a significant effect on fresh scrambled egg sensory characteristics and flavor volatiles. The contribution of both must be considered when producing egg substitutes.     

A New Protein Band Appearing in the Electrophoretic Pattern of Egg White Heated at Below 60°C

When egg white was heated to between 50° and 60°C, a new protein band appeared in its polyacrylamide gel electrophoretic pattern. The formation of the protein band in stored egg white was almost the same as that of fresh egg white. This protein band was shown to be induced by the interaction between macroglobulin and lysozyme during the egg white heating. The optimum temperature for its formation was between 54°C and 57°C. This band formation may be used as an indicator for heat treatment of egg white.     

高场强超声对蛋清液起泡特性的影响

为改善蛋清液的起泡性,采用不同超声功率(120,240 W)和超声时间(1,5,10,20,30 min)的高场强超声(20 kHz)对蛋清蛋白进行改性.结果表明,在功率120 W下超声处理20 min,蛋清蛋白的起泡性最佳(266.7％),是未处理蛋清的6.9倍.超声处理显著降低了蛋清液的表观黏度、表面张力和粒径大小...     

Effect of moderate spray drying conditions on functionality of dried egg white and whole egg

ABSTRACT:  Dried egg and egg-derived proteins have a range of applications in baking, dressings, and confectionery products. Egg powder was produced under high time–temperature scales (approximately 160 °C), which led to many changes in egg components, resulting in different functional properties of eggs after reconstitution. In this study, moderate operating conditions were selected to dry egg white and whole egg using a pilot-scale spray dryer. Functional properties changes were evaluated with an appropriate statistical technique. Major finding supports that spray drying of egg white at moderate conditions (air inlet temperature ranged from 110 to 125 °C) resulted in a product that enhanced considerably the water holding capacity of produced gels. Moreover, gel prepared with the dried samples was firmer than that of the fresh samples. Drying at a moderate scale allowed not only the increasing of the foaming capacity and the stability of foam but also an increase in their emulsifying capacity and stability of the emulsions.     

Quality of fresh and stored foam mat dried Mandarin powder

Foam mat drying is a lucrative process of mandarin (kinnow) pulp preservation in the form of powder. Foam mat drying of mandarin pulp experiments were carried out at 65, 75 and 85 °C drying air temperatures using carboxy methyl cellulose, milk and egg white as foaming agents at different concentrations levels to get dried mandarin powder. Quality of the reconstituted dried Mandarin pulp‐powder was evaluated for 6 month storage studies at an interval of 2 months for total sugars (%), ascorbic acid (mg 100 mL^?1), total acid (%), pH and microbial load (fungal and bacterial) using standard procedures. It was observed that total sugars, ascorbic acid and total acid were decreased whereas pH was slightly higher than the fresh pulp. There was minor bacterial growth noticed in all the treatments, which is within the permissible limit, furthermore no fungal growth was noticed during storage period.     

不同鲜蛋液对鲜切面品质影响的研究

在面条生产中添加鸡蛋可以改善面条的口感和营养价值.本实验分别添加鲜蛋液、蛋清液和蛋黄液制作鲜切面,通过测定其蒸煮品质及质构特性,研究了三种蛋液对鲜切面品质的影响.     

Role of pasteurisation heat treatments on rheological and protein structural characteristics of fresh egg pasta

The influence of egg pasteurisation and of thermal treatment(s) of fresh egg pasta on the protein network in the pasta were studied. Protein structural parameters were correlated with the physico-chemical and rheological characteristics of pasta. Twelve samples of fresh egg pasta were laboratory-produced, using raw or pasteurised whole egg, and either left untreated or submitted to one or two pasteurisation processes. Industrial pasteurisation of the eggs did not affect the protein network of pasta or its rheological and functional characteristics. Double thermal pasteurisation of egg pasta deeply influenced its structural characteristics, due to the formation of a tight protein network stabilised by disulfide bonds, in which ovalbumin plays an essential role. This tight protein network affected the cooking behaviour and the rheological properties of fresh egg pasta, decreasing weight increase upon cooking and break strain, while increasing break load and Young modulus. The indexes derived from these studies were applied to the characterisation of 24 commercial samples of fresh egg pasta. By using the Young modulus before and after cooking (rheological parameters) and protein solubility in buffer-saline (structural parameter), it was possible to discriminate three groups of samples as a function of the severity of their thermal treatment.     

Experimental studies of the influence of grain size, oxygen availability and organic carbon availability on bioclogging in porous media

Changes in the hydraulic properties of porous material due to bioclogging have been observed in many laboratory simulations and field studies. Because such changes in hydraulic properties influence the movement of fluids and contaminants, microbial ecology data are required for improved transport modeling. Here we investigate the effects of environmental variables previously shown to influence bioclogging, specifically oxygen availability, sediment grain size, and organic carbon (nutrient) concentration on the hydraulic properties of simulated subsurface environments. Our study provides evidence of a different clogging mechanism for aerobic and anaerobic microbial communities under high organic carbon concentrations (400 mg L(-1)). This work also suggests that the clogging mechanism operating in anaerobic microbial communities is more sensitive to carbon availability than that in the aerobic microbial communities. We found that grain size does have an effect on clogging, but it appears that there is a threshold carbon concentration, and therefore biomass, below which these effects are insignificant. Differences between the microbial communities that developed under different oxygenation conditions were detected using 16s rRNA analysis.     

PHYSICOCHEMICAL AND SENSORY ANALYSES ON EGG POWDER IRRADIATED TO INACTIVATE SALMONELLA AND REDUCE MICROBIAL LOAD

Egg powder was treated with 0, 2, 5 and 10 kGy of gamma radiation at 20C to inactivate Salmonella and to stabilize its microbial load. Microbial, physicochemical and sensory determinations were performed during 4 months of storage to select the optimal radiation dose to attain the objective without significantly reducing egg quality. Microbial results show that 2.0 kGy inactivated Salmonella and reduced microbial load to levels below those stipulated by the Argentine regulations. Physicochemical determinations of egg powder extracts for peroxide number, spectrophotometric measurements in the visible and ultraviolet regions, functional properties on sponge cakes made with egg powder (height, comprssion-relaxiation cycle parameters), foam stability and viscosity showed that gamma radiation at the dose of 2 kGy, did not cause significant changes in these parameters. Higher radiation doses (5 and 10 kGy) did increase rancidity, pigment loss and protein chain scission. Sensory determinations performed on egg powder, and on cakes manufactured with it, agreed with the physicochemical results. After 110 storage days, 2 kGy was the most suitable of the tested doses .     

Effects of microbial degradation of biofoulants on microfiltration membrane performance in a membrane bioreactor

In membrane bioreactors (MBRs) for wastewater treatment, membrane fouling, particularly biofouling caused by soluble microbial products (SMP), is a nuisance problem causing decreases in permeation flux. In a previous study, we identified primary biofoulants of microfiltration (MF) membranes in SMP as polysaccharides containing uronic acids that undergo inter- and intramolecular ionic cross-linking by polyvalent cations, forming a gelatinous mass that clogs membrane pores. In the present study, we therefore attempted to isolate biofoulant-degrading microorganisms from activated sludge on a polygalacturonic acid-overlaid agar medium and evaluate their efficiency for preventing biofouling of MF membranes. Among the isolates, the fungal strain HO1 identified as Phialemonium curvatum degraded 30% of polysaccharides containing uronic acids into smaller molecules in a SMP solution containing a high concentration of saccharides after 30 days of cultivation. Microfiltration tests using a laboratory-scale submerged MBR indicated that the filtration resistance of this degraded SMP solution was lower than that of the control SMP solution without fungal inoculation. Importantly, accumulation of gelatinous mass on the membrane responsible for biofouling was avoided in the SMP solution augmented with P. curvatum HO1 during the microfiltration test. This is the first report to describe a new method for avoiding biofouling of MBRs by microbial degradation of primary biofoulants.