PURIFICATION AND CHARACTERIZATION OF AN ALKALINE PROTEASE FROM THE VISCERA OF BOLTI FISH (TILAPIA NILOTICA)

An alkaline protease was extracted from acetone powder of the viscera of bolti fish (Tilapia nilotica) with distilled water, precipitated from the extract by 40–60% (NH₄)₂SO₄and then dialyzed. Enzyme homogeneity studies by polyacrylamide gel electrophoresis (PAGE) illustrated that the enzyme was homogenous. Sodium dodecyl sulfate–PAGE showed a molecular weight of 23.0 kDa. The optimal pH and optimal temperature were 8.0 and 45C, respectively, with casein as a substrate. A remarkable stability was observed under alkaline conditions (pH 6.0–10.0), where more than 90% of the enzyme activity was maintained. In the acidic region (pH 2.0–6.0), the enzyme retained more than 50% of its activity. Furthermore, the enzyme retained 85.4 and 41.8% of its activity after heating at 50 and 60C for 120 min, respectively, while the relative activity after heating at 70C for 120 min was 5.25%. The alkaline enzyme lost most of its activity when incubated at 80C for 30 min. A high percentage of total enzyme activity was inhibited when the enzyme was incubated with 50 mM of either soybean trypsin inhibitor or ethylenediaminetetraacetic acid. The presence of NaCl and CaCl₂at 10 mM concentration increased the enzyme activity by 6.9 and 10.6%, respectively.     

PURIFICATION AND CHARACTERIZATION OF A PROTEASE FROM THE PYLORIC CAECA OF MENHADEN (Brevoortia spp) AND MULLET (Mugil spp) FROM THE SOUTHWEST ATLANTIC REGION

A protease classified as trypsin was isolated and purified from the pyloric caeca of two species of fishes: Brevoortia spp (menhaden) and Mugil spp. (mullet). The characterization of both enzymes as trypsin was based on their molecular weight (24 kDa) determined by SDS-PAGE, their inhibition by some known trypsin inhibitors (PMSF, SBTI, TLCK and benzamidine), and their ability to hydrolyze the synthetic trypsin substrate N-α-Benzoyl-DL-arginine-p-nitroanilide (BAPA). Menhaden trypsin had maximum activity at pH 9.5 and was stable for 30 min between pH 6.0 and 10.0 at 0, 10 and 25C. On the other hand, mullet trypsin showed maximum activity at pH's from 7.8 to 9.0, and was stable over a wider pH range (7.0–10.0). The optimum temperature for menhaden and mullet trypsin was 63C and 60C respectively. Thermostability for menhaden trypsin was up to 50C, whereas mullet trypsin was stable up to 60C. The Km(BAPA) values for menhaden trypsin were conserved in the temperature range from 10 to 30C, while for mullet trypsin the Km(BAPA) was conserved between 10 and 25C.     

乳酸链球菌素的特性及其在食品中的应用

乳酸链球菌素是由乳酸链球菌产生的一种高效、无毒、安全、无副作用的天然食品防腐剂.介绍乳酸链球菌素的特性、效用及在食品加工中的应用.表明乳酸链球菌素在食品加工中是理想的食品防腐剂.     

谷氨酰胺转胺酶在食品加工中的应用

介绍了谷氨酰胺转胺酶的一些功能特性，并对其在食品中的应用进行了综述。     

PURIFICATION AND CHARACTERIZATION OF BACILLUS SUBTILIS JM-3 PROTEASE FROM ANCHOVY SAUCE

Bacillus subtilis JM‐3 was isolated from anchovy sauce naturally fermented in an underground cellar at 15 ± 3C for 3 years. The activity of the B. subtilis protease was highest in the 40–60% ammonium sulfate fraction. The yield of the purified protease was 5.3%, and its purification ratio was 35.6 folds. The molecular weight of the B. subtilis protease was 17.1 kDa, and its K_m and V_maxvalues were 1.75 μg/mL and 318 μM 1/min, respectively. The optimal temperature for protease activity was 60C, but optimal stability temperature was 30C. The optimal pH for protease activity and stability was 5.5. Therefore, the B. subtilis JM‐3 protease was classified as an acid protease. The relative activities of the B. subtilis JM‐3 protease were 69, 21 and 1.3% at 10, 20 and 30% NaCl concentrations, respectively. The best substrate for the B. subtilis JM‐3 protease was benzyloxycarbonyl‐glycine‐p‐nitrophenyl ester followed by bovine serum albumin. p‐Toluene‐sulfonyl‐L‐lysine chloromethylketone was the strongest inhibitor followed by soybean trypsin inhibitor, but N‐ethylmaleimide did not inhibit this enzyme. The B. subtilis JM‐3 protease was therefore presumed to be a trypsin‐like serine protease.     

OPTIMIZATION OF IMMOBILIZATION PROCESS ON CRAB SHELL CHITOSAN AND ITS APPLICATION IN FOOD PROCESSING

Optimization of immobilization process on crab shell chitosan was carried out. The chitosan purified from the crab shell was used as the matrix for the immobilization of α-galactosidase. The prepared matrix was activated with glutaraldehyde at different concentrations and different time intervals and coupling time was determined. Immobilization of α-galactosidase on crab shell chitosan resulted in 72% immobilization yield. The parameters like the effect of pH, temperature, thermal stability and storage stability were determined. The study revealed that immobilized enzyme shows better thermal and storage stability than the free enzyme. The performance of the free and immobilized α-galactosidase was tested in continuous stirred batch reactor to hydrolyze raffinose family oligosaccharides in soymilk. The oligosaccharide content of the soymilk was reduced by 77% in continuous reaction by immobilized α-galactosidase.

PRACTICAL APPLICATIONS

Chitosan used for the immobilization of α-galactosidase offers several advantages for enzyme immobilization and it contains all characteristic features for use as industrial material. Immobilization of one of the industrial important enzyme α-galactosidase, as it has many potential application in hydrolyzing raffinose series of oligosaccharides. The hydrolyzed soymilk after processing by immobilized α-galactosidase is free from flatus-inducing factors like raffinose and stachyose. It can be used as an alternative means for cow's milk for lactose intolerance, particularly among individuals in developing countries. As chitosan used is from the crustacean waste from the crab shell, the production and utilization of chitosan provides an economical alternative means of crustacean shell waste disposal sought worldwide.     

USE OF THE BIRD-LEIDER EQUATION IN FOOD RHEOLOGY

Shear stress development at inception of a constant shear rate was studied for marshmallow cream, peanut butter, squeeze margarine, tub margarine, whipped butter, whipped cream cheese and whipped dessert topping using the cone and plate geometry of the Rheometrics Mechanical Spectrometer. For most foods studied transient shear stresses showed increasing shear stress oversoots with increasing shear rate. At the highest shear rate of 100 s^?1, transient stresses were as large as 425% of the steady state shear stresses, with the actual magnitude of overshoot depending on the particular food investigated. The Bird-Leider equation was chosen to model this time dependent flow behavior by incorporating both steady viscous and elastic properties of the foods. By assuming that the viscosity function and primary normal stress coefficient followed power-law behavior, and constructing a time constant from the calculated parameters, the Bird-Leider model provided a good prediction of maximum and steady state stresses as well as the time at which they occur, but only a crude prediction of shear stress decay. The model supplied two more empirical constants “a” and “b” where “a” can be regarded as a pseudo-elastic modulus. Variation in “a” with shear rate shows that all materials studied are nonlinear viscoelastic.     

SUBJECT: ENERGY - ITS EFFICIENT USE AND CONSERVATION IN THE FOOD AND DAIRY INDUSTRY: ENERGY AND THE PRODUCTIVITY OF AGRICULTURE

The achievements of British agriculture in the last 100 years are considered and the remarkable increase in productivity evident during the last 30 years emphasized. It is shown that this was largely due to the increased reliance on inputs of resources from the industrial sector of the economy. Energy accounting methods are used to estimate this reliance, and an analysis is given of the energetics of British agriculture in terms firstly, of its biological efficiency and secondly, its industrial efficiency. These estimates are compared with those noted in other countries. The input of energy in terms of primary fuel equivalent to the industry is such that it takes 2–5 calories of fossil fuel to produce one calorie of food. The food industry is next considered and it is shown that this sector is even more expensive in terms of its dependence on fossil fuel reserves. The energy used in food provision and distribution is a large portion - nearly 10 per cent of our national energy requirements and the manpower employed is probably well in excess of 15 per cent of total work force     

大麦的营养价值及在食品业中的利用

简述了大麦的营养成分、提取物及其功能，并指出了大麦在食品工业中的应用现状，以及发展前景。     

PURIFICATION OF PEACH POLYPHENOL OXIDASE IN THE PRESENCE OF ADDED PROTEASE INHIBITORS1

Crude preparations of peach fruit (Prunus persica Batsch cv. Redskin) polyphenol oxidase (PPO) showed many apparent isoenzyme forms. Some of these forms were probably the result of proteolytic action of peach proteases while other forms were the result of association of PPO with carbohydrate materials. In the presence of protease inhibitors, Trasylol and phenylmethylsul-fonyl fluoride, three apparent isoenzyme forms of PPO were purified to homogeneity. The purification scheme included hydrophobic chromatography on phenyl sepharose CL-4B, hydroxylapatite chromatography, DEAE cellulose chromatography, and gel filtration on Ultrogel AcA 34. Minor contaminants remaining after these steps were separated from PPO by gel electrophoresis. The major PPO isoenzyme form (A) was purified 44 fold with an overall yield of 5.6% and contained no detectable carbohydrates. Isoenzyme forms A' and A' were purified 104 and 67 fold respectively, but still were associated with carbohydrate material. Cesium chloride centrifugation partially removed the carbohydrates associated with PPO A' and A'. Purified peach PPO A showed greater activity toward D-catechin (539%) and pyrogallol(l82%) than to catechol (100%). An apparent K₃ of 4, 0.3, and 2 mM was obtained with D-catechin, pyrogallol and catechol, respectively. The enzyme was severely inhibited by 10 μM 2,3-naphthalenediol (91%) and by 10 pM diethyl dithiocarbamate (100%).     

PURIFICATION AND CHARACTERIZATION OF PROTEASES FROM THE VISCERA OF MILKFISH (CHANOS CHANOS)

Proteases in acetone powder prepared from milkfish ( Chanos chanos ) viscera were extracted with deionized water and purified by ammonium sulfate fractionation, Sephadex G-75 gel filtration, repeated DEAE-Sephadex A-50 and CM-Sepharose CL-6B chromatography. Four fractions with caseinolytic activity, named A, B, C and D, were obtained from CM-Sepharose CL-6B and DEAE-Sephadex A-50 chromatography. The four proteases were purified to electrophoretic homogeneity. Substrate specificity studies indicated that proteases A and B were carboxypeptidase A-like and chymotrypsin-like enzymes, respectively; C and D were trypsin-like enzymes .

ABSTRACT

The optimal temperatures of proteases A, B, C and D for hydrolysis of casein were found to be 60, 60, 55 and 60°C, respectively. The optimal pH of protease A for hydrolysis of hippuryl-L-phenylalanine was 9.0, B for hydrolysis of acetyl-L-tyrosine ethyl ester was 8.0, C and D for hydrolysis of tosyl-L-arginine methyl ester was 8.0. The temperatures which inactivated 50% of enzymes in 5 min were 20°C for protease B; 51°C for protease C; 56°C for protease A; and 61°C for protease D. The molecular weights of proteases A, B, C, and D were 14,800, 16,800, 24,800 and 22,000 daltons, respectively.     

食品级丙酸钙的研制及其应用

研究了以氧化钙为钙剂与丙酸直接反应制备新型食品添加剂——丙酸钙的主要工艺条件，重点确定了丙酸过量系数和各反应物的最适浓度；同时，为了推动丙酸钙的普及，还对其在某些食品中的防腐效果进行了实验性研究     

EFFECT OF PROCESSING ON AMYLASE AND PROTEASE INHIBITOR ACTIVITY IN TROPICAL TUBERS

The effect of various processing methods on amylase, trypsin and chymo-trypsin inhibitory activities in tubers of Colocasia esculenta (taro), Xanthosoma sagittifolium (tannia), Solenostemon rotundifolius (Coleus, Chinese potato), Dioscorea esculenta (lesser yam) and Amorphophallus paeoniifolius (elephant foot yam) was studied. Among the different methods, frying was the most effective method of eliminating enzyme inhibitors from tubers. When cooked by boiling, partial retention (30 to 60%) of enzyme inhibitory activity was observed in certain tubers. Further reduction in inhibitory activity was observed in baked/pressure cooked tubers. The study indicated that processing decreased the inhibitor content significantly and the reduction of inhibitory activity was brought about by heat inactivation.     

免疫传感器在食品检测中的应用及相关思考

简述了免疫传感器的基本知识,综述了其在食品致病菌、毒素、农残和兽残检测中的应用.另外,就免疫传感器作了几点思考：免疫传感器的现状和缺陷,发展趋势和应用前景,商业化和产业化.     

超高压技术在食品工业中的最新研究进展

分析了超高压技术在食品工业中的应用现状，分析了目前超高压技术发展中存在的问题，提出了相应的发展对策和前景展望。     

人工模拟抗体在食品快速检测中的应用及目前存在的问题

人工模拟抗体通过对天然的抗体以仿生学的模仿而人工合成的对目标分子具有特异性的分子识别能力的元件.人工模拟抗体是通过功能单体和交联剂对模板分子进行分子印迹而制备得到.因而,人工模拟抗体也叫分子印迹聚合体.由于分子印迹聚合体的活性的稳定性和低廉的价格,因此,在食品的快速检测上得到了应用,如兽药残留、农药残留、微生物的快速检测.但是,由于它一种新型的分子识别材料,存在的一些问题,如对大分子物质的识别不稳定等,还有待于进一步的改善.     

人工模拟抗体在食品快速检测中的应斥及目前存在的问题

人工模拟抗体通过对天然的抗体以仿生学的模仿而人工合成的对目标分子具有特异性的分子识别能力的元件。人工模拟抗体是通过功能单体和交联荆对模板分子进行分子印迹而制备得到。因而，人工模拟抗体也叫分子印迹聚合体。由于分子印迹聚合体的活性的稳定性和低廉的价格，因此，在食品的快速检测上得到了应用，如兽药残留、农药残留、微生物的快速检测。但是，由于它一种新型的分子识别材料，存在的一些问题，如对大分子物质的识别不稳定等，还有待于进一步的改善。