Elevation of ceramide in Acetobacter malorum S24 by low pH stress and high temperature stress

Acetic acid bacteria have unique and highly pure membrane lipid components, such as 2-hydroxypalmitoyl-sphinganine (dihydroceramide) and can grow and produce acetic acid at around pH 3.0, suggesting that ceramide in cell membranes may be involved in the tolerance to acidic pH. Acetobacter malorum S24 was selected for the production of ceramide and grown in YPG medium containing 0.8% ethanol. Ceramide biosynthesis was induced at pH 4 and below, suggesting that ceramide biosynthesis is induced by low pH stress. Elevation of ceramide was also induced by high temperature stress (40–70 °C). After the strain was cultured in an optimal growth medium, the cells were collected and treated at pH 3 and 40 °C for 4 days, resulting in a 30-fold elevation of both the yield and content of ceramide.     

苹果低温高压膨化影响因素研究

以国光苹果为原料,探讨了苹果片厚度、预干燥后水分含量、膨化温度、抽空温度、抽空时间、压力差对苹果脆片产品水分含量、硬度、比容和色泽的影响。结果显示,膨化温度、抽空温度和抽空时间对苹果脆片产品水分含量影响极显著(P<0.01);除膨化温度外,其他因素对苹果脆片产品硬度影响极显著(P<0.01);苹果片厚度、抽空温度、抽空时间、压力差对苹果脆片产品比容影响极显著(P<0.01);除压力差外,其他因素对苹果脆片产品色泽影响极显著(P<0.01)。膨化苹果脆片的最佳工艺为:苹果片厚度5mm,水分含量30%,膨化温度100℃,抽空温度80℃,抽空时间0.5h,压力差0.3MPa。      

高新技术在常温流通低温肉制品中的应用

低温肉制品以其优质的口感,诱人的香味、丰富的营养必将在未来肉制品发展中成为主流产品。高新技术的应用可以解决低温产品常温流通的难题,因此,深入研究食品高新技术对于肉制品未来发展是必要的。     

谈低压法高纯度液体二氧化碳的生产

CO2是发酵法酒精的副产品。每生产100g酒精理论上同时生成95．5gCO2。由于不可避免的损失，实际可以回收的CO2约40—65g(因酒精生产的工艺而异)。国内实际达到的最高回收量约48g(1988．上海)。改造前我厂一直采用传统的高压法回收CO2，质量差、产量低、经济效益少。年产CO2 1500t，回收率只有5％。大量本来可以回收的CO2白白放空浪费了。     

Arsenic and selenium capture by fly ashes at low temperature

Arsenic and selenium compounds may be emitted to the environment during coal conversion processes, although some compounds are retained in the fly ashes, in different proportions depending on the characteristics of the ashes and process conditions. The possibility of optimizing the conditions to achieve better trace element retention appears to be an attractive, economical option for reducing toxic emissions. This approach requires a good knowledge of fly ash characteristics and a thorough understanding of the capture mechanism involved in the retention. In this work the ability of two fly ashes, one produced in pulverized coal combustion and the other in fluidized bed combustion, to retain arsenic and selenium compounds from the gas phase in coal combustion and coal gasification atmospheres was investigated. To explore the possible simultaneous retention of mercury, the influence of the unburned coal particle content was also evaluated. Retention capacities between 2 and 22 mg g(-1) were obtained under different conditions. The unburned coal particle content in the fly ash samples does not significantly modify retention capacities.     

Measurement of ionic calcium, pH, and soluble divalent cations in milk at high temperature

Dialysis and ultrafiltration were investigated as methods for measuring pH and ionic calcium and partitioning of divalent cations of milk at high temperatures. It was found that ionic calcium, pH, and total soluble divalent cations decreased as temperature increased between 20 and 80°C in both dialysates and ultrafiltration permeates. Between 90 and 110°C, ionic calcium and pH in dialysates continued to decrease as temperature increased, and the relationship between ionic calcium and temperature was linear. The permeabilities of hydrogen and calcium ions through the dialysis tubing were not changed after the tubing was sterilized for 1 h at 120°C. There were no significant differences in pH and ionic calcium between dialysates from raw milk and those from a range of heat-treated milks. The effects of calcium chloride addition on pH and ionic calcium were measured in milk at 20°C and in dialysates collected at 110°C. Heat coagulation at 110°C occurred with addition of calcium chloride at 5.4 mM, where pH and ionic calcium of the dialysate were 6.00 and 0.43 mM, respectively. Corresponding values at 20°C were pH 6.66 and 2.10 mM.     

Identification of transfer mechanisms involved in soiled CIP solutions regeneration at extreme pH and high temperature

Processing soiled cleaning in place (CIP) solutions induces large economic and environmental costs. Hence, recycling such solutions appears as an attractive alternative to reduce these costs. Recycling requires that a suitable green process is set which take into account the extreme physicochemical conditions prevailing during the cleaning of equipments of food or textile industries. Unfortunately, most of the processes used so far for water treatment are not efficient at high temperature (80–90 °C) or extreme pH (pH 1 and 14) which are commonly encountered in CIP. Purposely, Na-bentonite, in its crude or activated forms, was used to evaluate its potential for organic and mineral matter removal from such solutions. The resulting adsorption isotherms acquired at two temperatures, various pH values and salt concentrations were analyzed through the Langmuir, Freundlich and BET models. It is concluded that Na-bentonite action is based on a combination of adsorption and carrying capacity, the latter being related to its ability to coagulate at extremes pH. The efficiency of this innovative regeneration process combining adsorption/coagulation and flocculation was successfully tested by using synthetic industrial solutions mimicking those found in the dairy industry.     

Influence of temperature,water activity and pH on growth of some xerophilic fungi

The combined effects of water activity (aw), pH and temperature on the germination and growth of seven xerophilic fungi important in the spoilage of baked goods and confectionery were examined. Eurotium rubrum, E. repens, Wallemia sebi, Aspergillus penicillioides, Penicillium roqueforti, Chrysosporium xerophilum and Xeromyces bisporus were grown at 25, 30 and 37 degrees C on media with pH values of 4.5, 5.5, 6.5 and 7.5 and a range of water activities (aw) from 0.92 to 0.70. The aw of the media was controlled with a mixture of equal parts of glucose and fructose. Temperature affected the minimum aw for germination for most species. For example, P. roqueforti germinated at 0.82 aw at 25 degrees C, 0.86 aw at 30 degrees C and was unable to germinate at 37 degrees C. E. repens germinated at 0.70 aw at 30 degrees C, but at 25 and 37 degrees C, its minimum aw for germination was 0.74. C. xerophilum and X. bisporus germinated at 0.70 aw at all three temperatures. The optimum growth occurred at 25 degrees C for P. roqueforti and W. sebi, at 30 degrees C for Eurotium species, A. penicillioides and X. bisporus and at 37 degrees C for C. xerophilum. These fungi all grew faster under acidic than neutral pH conditions. The data presented here provide a matrix that will be used in the development of a mathematical model for the prediction of the shelf life of baked goods and confectionery.     

A study on the effects of high pressure and heat on Bacillus subtilis spores at low pH

Bacillus subtilis spore suspensions were subjected to pressure treatments at 100 and 600 MPa at 40 degrees C and over a pH range from 3 to 8. Inactivation of spores under these conditions was maximally 80% and was not increased at low pH. However, higher levels of inactivation were obtained when spores were first pressure treated at neutral pH and then exposed for 1 h to low pH. This large difference in inactivation could be explained by the finding that pressure-induced spore germination, which is known to occur at neutral pH, was inhibited at low pH (< 5). Pressure treatment at low pH made spores more sensitive to heat inactivation, suggesting that demineralized H-spores had been formed. Changes in spore core hydration and pH upon exposure of spores at low pH were studied in a more direct way using green fluorescent protein expressed in recombinant B. subtilis as a reporter protein, and it was confirmed that pressure and heat increase spore permeability for protons. Based on these results, the potential of low temperature, high pressure processes for spore inactivation in acid products is discussed.     

酶高温轧蒸退浆工艺

对棉织物的酶高温轧蒸工艺进行研究，讨论了酶浓度、轧余率、轧酶温度、酶液pH值和汽蒸时间等因素对退浆效果的影响，初步确定淀粉酶退浆工艺为：淀粉酶L401．5-2g／L，轧余率100％～110％，室温轧酶（轧前先浸轧60℃热水），酶液pH值约6．5，汽蒸时间15min，汽蒸温度100—102℃。比较碱轧蒸退浆工艺发现，酶退浆工艺退浆率较高，可达7级以上，但毛效、润湿性和白度稍低。     

Feasibility of using dialysis for determining calcium ion concentration and pH in calcium-fortified soymilk at high temperature

Abstract: Dialysis was performed to examine some of the properties of the soluble phase of calcium (Ca) fortified soymilk at high temperatures. Dialysates were obtained while heating soymilk at temperatures of 80 and 100 °C for 1 h and 121 °C for 15 min. It was found that the pH, total Ca, and ionic Ca of dialysates obtained at high temperature were all lower than in their corresponding nonheated Ca‐fortified soymilk. Increasing temperature from 80 to 100 °C hardly affected Ca ion concentration ([Ca²⁺]) of dialysate obtained from Ca chloride‐fortified soymilk, but it increased [Ca²⁺] in dialysates of Ca gluconate‐fortified soymilk and Ca lactate‐fortified soymilk fortified with 5 to 6 mM Ca. Dialysates obtained at 100 °C had lower pH than dialysate prepared at 80 °C. Higher Ca additions to soymilk caused a significant (P≤ 0.05) reduction in pH and an increase in [Ca²⁺] of these dialysates. When soymilk was dialyzed at 121 °C, pH, total Ca, and ionic Ca were further reduced. Freezing point depression (FPD) of dialysates increased as temperature increased but were lower than corresponding soymilk samples. This approach provides a means of estimating pH and ionic Ca in soymilks at high temperatures, in order to better understand their combined role on soymilk coagulation.     

耐高温活性干酵母在高温与低温蒸煮的应用

通过对耐高温酒用活性干酵母在高温与低温条件下蒸煮酒精生产对比试验,经分析得出耐高温酒用活性干酵母在低温蒸煮条件下酒精生产优于在高温蒸煮条件下酒精生产。     

Ironmaking with ammonia at low temperature

This paper describes the reduction of hematite with ammonia for ironmaking, in which the effect of temperature on the products was examined. The results showed that the reduction process began at 430 °C during heating, and with an increase in temperature, the reduction mechanism changed apparently from a direct reduction of ammonia (Fe(2)O(3) + 2NH(3) → 2Fe + N(2) + 3H(2)O) to an indirect reduction via the thermal decomposition of ammonia (2NH(3) → N(2) + 3H(2), Fe(2)O(3) + 3H(2) → 2Fe + 3H(2)O) at temperatures over 530 °C. The final product obtained at 600 and 700 °C was pure metallic iron, in contrast with that formed at 450 °C, that is, a mixture of metallic iron and iron nitride. The results suggest the possibility of using ammonia as a reducing agent for carbonless ironmaking, which is operated at a much lower temperature than 900 °C in conventional coal-based ironmaking.     

Investigation of mechanisms of oxidation of EDTA and NTA by permanganate at high pH

Permanganate has been used for oxidation of nuclear wastes containing chelating agents such as ethylenediaminetetraacetic and nitrilotriacetic acids (EDTA and NTA) to improve separation of radionuclides and heavy metals from the wastes, butthe mechanisms of degradation of these and related organic ligands at high pHs have not been studied. EDTA, NTA, and the model compound ethylenediamine (EN) were found to be readily oxidized by permanganate at pH 12-14. The reduction of permangante was accompanied by formation of unstable manganate and dispersed MnO2 particles, which constituted the final product of permanganate reduction. The yields and speciation of EDTA, NTA, and EN breakdown products were affected by the pH and permanganate dose. Iminodiacetic acid (IDA), oxalate, formate, and ammonia were the predominant EDTA and NTA oxidation products. Mineralization of EDTA, NTA, and EN to CO2 was more significant at pH 12. At pH 14 formation of oxalate and deamination to NH3 were the most important reactions. IDA was released upon the oxidation of both EDTA and NTA, but EDTA oxidation yielded no ethylenediaminediacetic acid (EDDA). The speciation of the reaction products indicated that the ethylene group in EDTA was the preferred attack site in oxidations by alkaline permanganate.     

Study of starch fermentation at low pH by Lactobacillus fermentum Ogi E1 reveals uncoupling between growth and alpha-amylase production at pH 4.0

Lactobacillus fermentum Ogi E1 is an amylolytic heterofermentative lactic acid bacterium previously isolated from ogi, a Benin maize sourdough. In the present study, the effect of different pH between 3.5 and 6.0 on starch fermentation products and alpha-amylase production was investigated. Whereas a pH of 5.0 was optimum for specific growth rate and lactic acid production, growth was only slightly affected at suboptimal pH of 4.0 and 6.0. Over a pH range of 6.0 to 3.5, yields of product formation from substrate and of biomass relative to ATP were constant. These results showed that L. fermentum Ogi E1 was particularly acid tolerant, and well adapted to the acid conditions that develop during natural fermentation of cereal doughs. This acid tolerance may partly explain the dominance of L. fermentum in various traditional African sourdoughs. Surprisingly, alpha-amylase production, unlike growth, dropped dramatically when the strain was cultivated at pH 4.0 with starch. With maltose as substrate, the yield of alpha-amylase relative to biomass remained unchanged at pH 4.0 and 5.0, unlike that observed with starch. Based on the distribution of enzyme activity between extra- and intracellular fractions and fermentation kinetics, it appears that starch was first hydrolyzed into dextrins by alpha-amylase activity, and maltose was produced from dextrins by extracellular enzyme activity, transferred into the cell and then hydrolyzed into glucose by intracellular alpha-glucosidase.     

涤纶织物低温染色

研究自制低温染色助剂对涤纶织物分散染料上染性能及染色牢度的影响.结果表明,低温染色助剂能显著提高分散染料在涤纶织物上的上染性能,且匀染性及各项牢度良好.     

Functional properties of whey proteins microparticulated at low pH

The main aim of the study was to assess the effect of microparticulation at low pH on the functionality of heat-denatured whey proteins (WP). Spray-dried, microparticulated WP (MWP) powders were produced from 7% (wt/wt) WP dispersions at pH 3, acidified with citric or lactic acid, and microfluidized with or without heat denaturation. Nonmicroparticulated, spray-dried powders produced at neutral pH or pH 3 served as controls. The powders were examined for their functional and physicochemical properties. Denatured MWP had an approximately 2 orders of magnitude reduction in particle size compared with those produced at neutral pH, with high colloidal stability indicated by substantially improved solubility. The detection of monomeric forms of WP in PAGE also confirmed the particle size reduction. Microparticulated WP exhibited enhanced heat stability, as indicated by thermograms, along with better emulsifying properties compared with those produced at neutral pH. However, MWP powders created weaker heat-induced gels at neutral pH compared with controls. However, they created comparatively strong cold acid-set gels. At low pH, a combination of heat and high hydrodynamic pressure produced WP micro-aggregates with improved colloidal stability that affects other functionalities.     

Pectin stabilization of soy protein isolates at low pH

The stabilizing behaviour of pectins in acidified dispersions of soy protein was studied. Objective of this work was to understand if different soy isolates and different pectins show differences in stability. The behaviour of a commercially available isolated soy protein (ISP) was compared to that of a soy protein in the laboratory. At pH 3.8 while suspensions of commercial ISP showed significant precipitation, the native SPI (prepared in the laboratory) was much more stable against precipitation. High methoxyl pectin (HMP) had better stabilization behaviour than low methoxyl pectin (LMP). A higher amount of HMP was needed to avoid protein precipitation of native SPI, compared to that used for commercial ISP. It was demonstrated that at low pH pectin forms soluble complexes with SPI through electrostatic interactions.     

高水分成品大米低温储存及低温解除后品质变化研究

通过对东北高水分粳米低温储存及解除低温后的试验研究,探索高水分大米低温储存品质变化规律。结果表明:大米初始水分为17.54%,在温度低于15℃、相对湿度60%~70%的条件下,储存10个月,大米水分维持在16.0%,脂肪酸值低于25 mgKOH/100 g,大米品质无明显劣变,在宜存范围内。储存过程中大米L值降低,b值升高,a值变化无明显规律。TPA质构分析显示,蒸煮米饭硬度增大,黏性、弹性下降,内聚性增加。储存6个月后,各项指标发生明显变化。低温解除后,在夏季,高水分大米储存1个月后发生霉变,水分、脂肪酸值、色差值均发生明显变化。扫描电镜观测结果表明:随储藏时间延长,米粒表面裂纹空隙增大,淀粉粒裸露,去胚部后形成空洞。胚乳细胞表面小孔增多变大,细胞表面被包裹的复合淀粉体之间的界限变得模糊,蛋白质膜明显翘起。