An optimised micro-titer plate method for characterisation of endogenous rye phytase under industrial rye bread making conditions

A modified rapid method for the determination of phytase activity has been developed by measurements of molybdenum blue complex using micro-titer plate reader. This method requires only a small amount of extract, and it is possible to make more replicates at the same time and thus a better sampling and a higher capacity compared to measurements on spectrophotometer, which is traditionally used for those measurements. The extraction time was reduced by 36% compared to standard method and the extinction coefficient for molybdenum blue complex was determined instead of using P-standard solutions. To demonstrate the new method it was applied to the determination of the activity of phytase at a range of pH values and temperatures relevant to the rye bread making process. The activity of rye phytase was 320 nkatal g⁻¹ grains (pH 5.5, 37 °C). The temperature optimum was 45–55 °C and the pH optimum 6.0. The study revealed that the rye phytase is very pH-sensitive and quite stable at different temperatures during the whole bread-making process. The enzyme activity of the endogenous rye phytase is optimal for a total degradation of phytic acid during rye bread making and thus the full bioavailability of phytate-bound minerals.     

A new, simple method for the production of meat-curing pigment under optimised conditions using response surface methodology

The production of cured meat pigment using nitrite and ascorbate in acidic conditions was evaluated. HCl, ascorbate and nitrite concentrations were optimised at three levels using the response surface method (RSM). The effects of process variables on the nitrosoheme yield, the wavelength of maximum absorbance (λ(max)), and L*, a* and b* values were evaluated. The response surface equations indicate that variables exerted a significant effect on all dependent factors. The optimum combinations for the reaction were HCl=-0.8, ascorbate=0.46 and nitrite=1.00 as coded values for conversion of 1mM hemin to nitrosoheme, by which a pigment yield of 100%, which was similar to the predicted value of 99.5%, was obtained. Likewise, the other parameters were not significantly different from predicted values as the λ(max), L*, a* and b* values were 558nm, 47.03, 45.17 and 17.20, respectively. The structure of the pigment was identified using FTIR and ESI/MS.     

A new,simple method for the production of meat-curing pigment under optimised conditions using response surface methodology

The production of cured meat pigment using nitrite and ascorbate in acidic conditions was evaluated. HCl, ascorbate and nitrite concentrations were optimised at three levels using the response surface method (RSM). The effects of process variables on the nitrosoheme yield, the wavelength of maximum absorbance (λ_max), and L*, a* and b* values were evaluated. The response surface equations indicate that variables exerted a significant effect on all dependent factors. The optimum combinations for the reaction were HCl = − 0.8, ascorbate = 0.46 and nitrite = 1.00 as coded values for conversion of 1 mM hemin to nitrosoheme, by which a pigment yield of 100%, which was similar to the predicted value of 99.5%, was obtained. Likewise, the other parameters were not significantly different from predicted values as the λ_max, L*, a* and b* values were 558 nm, 47.03, 45.17 and 17.20, respectively. The structure of the pigment was identified using FTIR and ESI/MS.     

Behaviour of polydiacetylene vesicles under different conditions of temperature, pH and chemical components of milk

Blue polydiacetylene vesicles were studied with regard to their behaviour under variations in storage temperature, heating, potentiometric titration and in the presence of chemical components of milk, to evaluate their application as a sensor in the food industry. Vesicles were prepared using 10,12-pentacosadienoic acid (PCDA)/1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC). Their changes were monitored using UV-Vis absorption. Temperatures not exceeding 25°C did not cause colour change in PCDA/DMPC vesicles for a period of up to 60days of storage. Heating for 10min at 60 and 90°C, exposure to pH higher than 9.0 and the simulant solutions of the whey proteins, β-lactoglobulin and α-lactalbumin, promoted colour change from blue to red for the vesicles studied. The effects of routine factors on the characteristics and stability of polydiacetylene vesicles is important in defining the parameters related to their application as a sensor for the food industry.     

Accelerated kinetics study of neohesperidine DC hydrolysis under conditions relevant to high-temperature-processed dairy products

 The degradation of neohesperidine DC in solution as a function of temperature (70–100 °C) and pH (6–7) was studied in order to estimate losses during thermal processing of non-fermented milk-based products. First order rate constants were observed in all the conditions tested. An increase in the pH from 6 to 7 produced an increase in rate constants by a factor of 5. These data were used to predict losses that would occur during conditions prevailing during the manufacture of non-fermented dairy products. Results indicate that neohesperidine DC would withstand these heat treatments without significant degradation. Received: 19 December 1995/Revised version: 14 June 1996     

Prediction of short peptides composition by RP-HPLC coupled to ESI mass spectrometry

The combination of reversed-phase chromatography and electrospray mass spectrometry was used to predict the amino acid composition of low molar weight peptides present in a complex mixture of rapeseed protein hydrolysates. First, amino acid retention times on a hydrophobic stationary phase were evaluated to determine hydrophobicity coefficients for each amino acid and then global hydrophobicity coefficients were established for standard peptides. In this way, a correlation between peptide hydrophobicity coefficients and retention time was established. Then, a C language program was developed to calculate all potential amino acid combinations from the mass of a peptide (molar mass < 1000 Da) and determine theoretical hydrophobicity coefficients corresponding to these combinations. Comparison between the theoretical retention time determined by the model and the experimental retention time resulted in the establishment of a sorted potential composition table. This methodology has been applied to two different rapeseed protein hydrolysates peptides that have been purified and sequenced.     

Enhancement of the cytotoxicities and antioxidative activities of white ginseng extract by hydrolysis under mild acidic conditions

White ginseng extract (WGE) was hydrolyzed with organic acids to increase the yield of ginsenoside Rg₃ which has high bio-functional activities. The condition of hydrolysis by citric acid was studied to maximize a production of ginsenoside Rg₃. The total content of ginsenoside Rg₃ in WGE treated with 10% citric acid at 110°C for 1 h was 10-folds greater than that of commercial extract. The antitumor and antioxidant activities of WGE and the acid-hydrolysates were evaluated via an MTT assay and the DPPH method, respectively. At 1.0 mg/mL, hydrolysates inhibited the proliferation of AGS and Hep-2 cells by more than 90%, but did not inhibit their growth. It suggests that citric acid hydrolysis enhances the content of Rg₃. In addition, the acid hydrolysates evidenced a free radical scavenging activity of 80% at a concentration of 4.0 mg/mL, while WGE exhibited only a 49% free radical scavenging activity at the same concentration.     

海蜇皮水解条件的研究

以肽含量为指标,对海蜇皮的水解用酶进行了选择,认为风味蛋白酶和真菌酸性蛋白酶水解效果较好,并对这两种酶进行了单因素实验,结果表明:底物浓度为2%时,风味蛋白酶较好的水解条件为45℃、pH6.0、加酶量2700U/g,水解90min,肽提取率可达62.5%;真菌酸性蛋白酶较好的水解条件为55℃、pH2.5、加酶量2000U/g,水解90min,肽提取率可达74.7%。     

鲶鱼骨肉泥的酶解工艺优化

利用鲶鱼副产物（鱼头、鱼皮、鱼骨和碎肉等）制备的骨肉泥为实验对象,以多肽得率和钙溶出率为考察指标进行Box-Behnken响应面实验设计,探究胃蛋白酶的酶解时间、加酶量和液料比三因素对酶解效果的影响。通过所得的结果和二次多项回归方程确立了最优的工艺条件:液料比（水∶骨肉泥,m∶m）是6.73∶1,胃蛋白酶的加酶量7000 U/g,酶解温度37℃,p H为3.0,酶解时间6 h。此条件酶解骨肉泥得到的酶解液中,多肽得率为43.07%,钙溶出率为44.62%。      

Modeling mass transfer during osmotic dehydration of strawberries under high hydrostatic pressure conditions

Simultaneous application of high hydrostatic pressure (200–400 MPa) during osmotic dehydration of strawberries was studied in this investigation. The high hydrostatic pressure treatment improved the diffusion coefficients of water and soluble solids compared to atmospheric pressure operation. Effects of process pressure on diffusion coefficients were achieved through an Arrhenius-type equation. Mathematical modeling of mass transfer was performed applying Newton, Henderson–Pabis, Page and Weibull models. Based on statistical results, the Weibull model gave the best goodness of fit on the experimental data under the studies' operative conditions.Industrial relevance: This article deals with the mathematical modeling of mass transfer during simultaneous high hydrostatic pressure treatment and osmotic dehydration of strawberries. Transfer of water and soluble solids during this combined process were satisfactorily simulated with the Weibull model. Results indicated that application of this innovative technology improved strawberries dehydration rates compared to atmospheric pressure operation resulting in a dried fruit with intermediate moisture content ready to be used as input material of further processes.     

Optimization of lipase activity under various chemo-physical conditions for hydrolysis of polyester fabric using multiple statistical approaches

Abstract

Polyester is known to be one of the most abundantly used fabrics. However, its surface is hydrophobic which restricts its wide acceptability and efficient processability. Therefore, many approaches have been adopted to overcome this shortcoming. This study dealt with the optimization of lipase activity under various chemo-physical conditions for hydrolysis of polyester fabric using statistical approaches. The study undertakes the effect of pH, temperature and surfactant type on Aspergillus niger lipase activity using Taguchi L₉ orthogonal array. Afterward, polyester was hydrolyzed under optimized conditions using central composite approach. It was found that lipase activity was higher at acidic pH and 50?°C with nonionic surfactant (Tween 80). The hydrolysis of polyester was carried out by varying lipase and non-ionic surfactant concentrations, and by changing the process time on a lab scale launder-o-meter. The significance of each input variable, squared and interaction terms on hydrolytic activity, weight loss, tensile strength and absorbency time was determined. Response optimizer was drawn to predict the effect of each input factor on output factor during hydrolysis of polyester which can be very beneficial for industrial processing.     

菜籽蛋白的酶水解：复合风味蛋白酶水解条件的研究

用响应面分析方法（RSM）对影响菜籽蛋白酶水解的因素进行分析,得到复合风味蛋白酶Flavorzyme的最佳酶水解条件为温度55.5℃,pH6.2。酶与底物浓度比（E/S）74.31LAPU/g,底物浓度12.0%（W/V）,水解时间3h,最佳酶水解条件下的水解度为26.4%。在最佳酶水解条件下对水解度和时间的关系进行了研究,证实了预测值和实测值是一致的。     

复合酶酶解条斑紫菜工艺条件及优化

条斑紫菜是一种具有很高营养价值和多种活性物质的藻类。以酶解液中游离氨基酸含量为指标,结合酶配比、酶加量、pH值、酶解温度、酶解时间等因素,确定复合酶对条斑紫菜酶解工艺,并在此基础上进行条件优化。试验结果表明,条斑紫菜酶解优化条件:复合酶配比1:3:3,复合酶加量为条斑紫菜总量的0.8%,酶解温度为45℃,酶解时间为170min,pH值为6.5。经优化后条斑紫菜酶解液中游离氨基酸含量为0.541g/100mL。     

The tinctorial stability of safflor yellow B under experimentally controlled model conditions

Several factors affecting the stability of safflor yellow B tincture were studied in experimentally scheduled model systems. Higher temperatures act on the colour more unfavourably than lower ones. UV light promotes bleaching of the pigment, pH is a decisive factor for preserving safflor yellow B, which deteriorated more rapidly under alkaline conditions. The pigment is sensitive to atmospheric O₂. Metal cations affect the stability of safflor yellow B: trivalent manganese and divalent iron reduce the orange-yellow colour most strikingly. The tinctorial stability and the practical utility of safflor yellow B are outlined on the basis of the experimental data.

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Die Farbstabilität von Safflor-Gelb B unter experimentell kontrollierten Modellkonditionen

Zusammenfassung In experimentell kontrollierten Modellsystemen wurden verschiedene Faktoren, die sich auf die Stabilität von Safflor-Gelb B auswirken, kontrolliert. Hohe Temperaturen und UV-Licht wirken bleichend. Das Pigment ist sehr pH-empfindlich, besonders im Alkalischen. Auch Sauerstoff zerstört es. Von den Metallionen wirken insbesondere Mn³⁺ und Fe²⁺ bleichend. Farbbeständigkeit und praktische Brauchbarkeit von Safflor-Gelb B werden diskutiert.

     

Short communication: Urea hydrolysis in dairy cattle manure under different temperature,urea, and pH conditions

The objective of the study was to quantify the rate of urea hydrolysis in dairy cattle manure under different initial urea concentration, temperature, and pH conditions. In particular, by varying all 3 factors simultaneously, the interactions between them could also be determined. Fresh feces and artificial urine solutions were combined into a slurry to characterize the rate of urea hydrolysis under 2 temperatures (15°C and 35°C), 3 urea concentrations in urine solutions (500, 1,000, and 1,500 mg of urea-N/dL), and 3 pH levels (6, 7, and 8). Urea N concentration in slurry was analyzed at 0.0167, 1, 2, 4, 6, 8, 12, 16, 20, and 24 h after initial mixing. A nonlinear mixed effects model was used to determine the effects of urea concentration, pH, and temperature treatments on the exponential rate of urea hydrolysis and to predict the hydrolysis rate for each treatment combination. We detected a significant interaction between pH and initial urea level. Increasing urea concentration from 1,000 to 1,500 mg of urea-N/dL decreased the rate of urea hydrolysis across all pH levels. Across all pH and initial urea levels, the rate of urea hydrolysis increased with temperature, but the effect of pH was only observed for pH 6 versus pH 8 at the intermediate initial urea concentration. The fast rates of urea hydrolysis indicate that urea was almost completely hydrolyzed within a few hours of urine mixing with feces. The estimated urea hydrolysis rates from this study are likely maximum rates because of the thorough mixing before each sampling. Although considerable mixing of feces and urine occurs on the barn floor of commercial dairy operations from cattle walking through the manure, such mixing may be not as quick and thorough as in this study. Consequently, the urea hydrolysis rates from this study indicate the maximum loss of urea and should be accounted for in management aimed at mitigating ammonia emissions from dairy cattle manure under similar urea concentration, pH, and temperature conditions reported in this experiment.     

Epimerisation and hydrolysis of catechins under ultrasonic treatment

This study investigated the influence of ultrasonic treatments on the chemical conversions of catechins. Ultrasound treatments significantly enhanced the epimerisation and the hydrolysis of catechins in both the catechins solution and the tea extract solution. Catechins are more stable in the tea extract solution compared to the catechins solution. The conversion of catechins induced by ultrasound can be controlled by temperature and pH. Regard to the pyrogallol-type catechins, both the epimerisation and the hydrolysis were enhanced at the higher temperatures (60 and 70 °C) and the acidic condition (pH 6). The epimerisation and the hydrolysis of (-)-epigallocatechin gallate (EGCG) improved by 47% and 18%, respectively, when the temperature rose from 50 to 70 °C. Compared to pH 8, the epimerisation and the hydrolysis of EGCG at pH 6 improved by 27% and 39%, respectively. This study can be utilised to develop appropriate ultrasound-assisted method to produce particular catechin monomers.     

Glucose Isomerase and Its Behaviour under Hydrogenation Conditions

A survey is given of glucose isomerase, its sources, its mechanism of isomerization and its data and properties in three different immobilized forms. In addition, the effect of a number of parameters on the activity of immobilized glucose isomerase has been investigated, e. g. hydrogen pressure, Mg(II) and Ca(II), transition metal ions, borate and sugar alcohols. Immobilized glucose isomerase remains sufficiently active under hydrogenation conditions to maintain D -glucose and D -fructose in equilibrium. D -Glucitol, in contrast to D -mannitol, has some inhibiting effect on the enzyme action. The D -glucose/D -fructose equilibrium constant is independent of the total sugar concentration (between 0.2 – 2.2-M).