Pressure-Temperature Inactivation of Lipoxygenase in Green Peas ((Pisum sativum): A Kinetic Study

ABSTRACT Kinetics of lipoxygenase (LOX) inactivation in green peas (Pisum sativum) by temperature and/or pressure was studied at different levels of food complexity, namely in green pea juice and in intact vegetables (in situ study). Pea LOX in both matrices was irreversibly inactivated either by thermal or by combined pressure-temperature treatment, and the inactivation followed a first- order reaction. Pressure levels below 200 MPa retarded thermal inactivation of LOX at temperatures above 60 °C. Moreover, above 60 °C, enzyme activation under pressure occurred prior to inactivation. At elevated pressure, LOX inactivation rate could be accelerated by a temperature increase above 10 °C as well as by a temperature decrease below 10 °C. The pressure-temperature dependence of the LOX inactivation rate constants both in green pea juice and in intact green peas was described successfully using the same mathematical model. On the basis of this mathematical model, an iso-rate contour diagram for LOX inactivation in green pea juice and in intact green peas was constructed.     

Volatile Flavor Components from Green Peas (Pisum Sativum).

SUMMARY— The volatile alcohols of unblanched frozen green peas were separated from the total volatiles by chromatography on silica gel at 0°C and examined by combined gas chromatography-mass spectrometry and where possible by infrared spectroscopy. Thirteen saturated and nine unsaturated alcohols were positively identified: methanol, ethanol, propan-l-01, butan-1-01, butan-2-01, 2-methylpropan-l-01, pen-tan-l-01, pentan-3-01, P-methylbutan-1-01, 3-methylbutan-l-01, hexan-l-01, heptan-l-01, octan-l-01, pent-l-en-3-01, cis and trens pent-2-en-l-01, cis and trans hex-3-en-l-01, trans hept-2-en-l-01, trans act-2-en-l-01, act-1-en-3-01 and cis non-3-en-l-01. Several other alcohols were also present and, of these, trans hex-2-en-l-01, cis and trans hept-3-en-l-01 and nonan-l-01 were tentatively identified.
The interconnecting system between gas chromatograph and mass spectrometer permitted the collection, for IR analysis, of material from the identical gas chromatographic peak on which the mass spectrum was obtained.     

Air Classification of Peas (Pisum sativum) Varying Widely in Protein Content

Four samples of field peas, ranging in protein content from 14.5–28.5% (dry, dehulled seed basis), were pin milled and air classified yielding protein concentrates and starch concentrates containing 33.6–60.2 and 3.8–11.3% protein, respectively. The protein content of the dehulled peas were negatively correlated with their starch content (49.7–59.8%), lipid content (3.0–4.1%) and cell wall material (CWM) content (7.1–9.6%). The % protein in all air classified fractions was positively correlated to % protein in the dehulled peas, whereas, lipid and CWM content was negatively correlated. Air classification at lower air flows (smaller cut sizes) resulted in protein and starch fractions containing higher levels of protein. Starch separation efficiency and protein separation efficiency generally increased with increasing protein content.     

Glycine Betaine-Mediated Protection of Peas (Pisum sativum L.) During Blanching and Frozen Storage

We used glycine betaine (5–20% w/v) for blanching green peas (100°C, 60 s), and their subsequent freezing and storage (–20°C, 90 days). Blanching after the addition of glycine betaine at ≥10% (w/v) followed by a 90 day storage period which resulted in the most desirable outcome: higher vitamin C levels, a superior green color, enhanced organoleptic quality and texture, and improved retention of peroxidase and lipoxygenase activity relative to control peas (no glycine betaine added). Microscopic characterizations of control and treated peas revealed that glycine betaine acts as a cryoprotectant which maintains cellular integrity. Glycine betaine (10% w/v) could be used commercially for production of frozen peas with better quality attributes.     

Essential Elements and Cadmium and Lead in Fresh and Canned Peas (Pisum sativum L.)

Sixteen essential elements along with cadmium and lead were determined in fresh and canned peas (Pisum sarivum L.). Samples were taken during the canning process to determine where changes in element content occurred. The concentration of each sample was compared statistically to other samples taken at different stages of the process. Canned peas contained significantly lower concentrations of calcium, copper, iron, magnesium, manganese, phosphorus, potassium, silicon, and zinc than fresh peas. As sodium chloride was added during the canning process, higher concentrations of chloride and sodium were found in the canned product. A 100g serving of drained canned peas supplied less than 11% of the RDAs or of the estimated safe and adequate daily dietary intakes except for chloride and sodium. Retention of all elements, except chloride and sodium, ranged from 24–86%.     

Digestibility and Nitrogen Balance in Rats Given Dried or Toasted Peas (Pisum sativum) of Different Years of Harvest

Experiments with Wistar rats were performed to study the digestibility of nutrients and nitrogen (N) utilization of dried and toasted (130°C, 3–4 min) peas (Pisum sativum spp hortense) cultivar Solara, harvested in two different years. Diets were formulated containing 111–128 g kg^-1 dietary fibre and ∽170 g kg^-1 crude protein with peas as the sole source of polysaccharides and N, and unsupplemented or supplemented with antibiotics (Nebacitin) to reduce the gastrointestinal microflora. In one of the harvests, the digestibility of starch was almost complete and unaffected by addition of Nebacitin. In the other harvest of peas, starch digestibility was very high (98·6–99·3%) in the rats with normal microflora, and reduced to 96% by addition of the antibiotics. The digestibility of non-starch polysaccharides (NSP) was 71·2–72·8% in one harvest and 73·6–76·4% in the other. The digestibilities decreased by addition of Nebacitin (25·7–38·5%). Toasting affected the digestibility of some NSP monomers, but with different tendencies in the two harvests. The N metabolism was affected by toasting in one harvest, while there was no effect in the other. The effect of toasting on BV of peas and the availability of lysine were studied in one of the pea harvests. No effect was observed. © 1997 SCI.     

豌豆酯酶的纯化和酯酶活性表征及其对农药的敏感性

由于食品和环境中的农药残留对人体健康构成威胁,使得发展农残快速检测方法显得十分重要,从植物中发现新的酶源有助于降低酶抑制法快速检测农药的成本。实验从豌豆中分离纯化豌豆酯酶,并进行了酶类鉴别、特性表征和农药敏感性研究。纯化后的豌豆酯酶分子质量约为26. 0 k Da,具有较高的酯酶活性。通过底物和抑制剂特异性试验,将豌豆酯酶分类为羧酸酯酶。豌豆酯酶在质量浓度为0. 45μg/m L,缓冲液p H 6. 5和反应温度40℃时,表现出最好的催化活性。豌豆酯酶可以被有机磷和氨基甲酸酯类农药抑制。豌豆酯酶属于B型酯酶,可用于酶抑制法检测有机磷和氨基甲酸酯类农药残留,且经过纯化的豌豆酯酶满足大多数农药最大残留限值(MRL)检测的要求。     

The Variation in Content and Changes during Development of Soyasaponin I in Dehulled Swedish Peas (Pisum sativum L)

The variation in content and changes during development of soyasaponin I in dehulled Swedish peas (Pisum sativum L) were investigated. The content of soyasaponin I in 40 dehulled pea samples ranged from 0·82 to 2·5 g kg^-1 with a mean of 1·5 g kg^-1. No significant differences in soyasaponin content were found between light- and dark-coloured peas. No soyasaponin I was found in the hulls. The content of soyasaponin I in the dehulled peas decreased considerably during maturation. Two light-coloured varieties had a higher initial content and a much more pronounced decrease during development than a dark-coloured variety. © 1997 SCI.     

黄瓜过氧化物酶的分离纯化及酶学性质

新鲜的黄瓜经匀浆、抽提、硫酸铵沉淀、CM-Sepharose 离子交换层析、Superdex-200凝胶过滤层析后获得电泳纯的过氧化物酶。该酶的比活力、回收率及纯化倍数分别为64 177.67 U/mg、9.58%、61.93。该酶的分子质量为41.15 kD,亚基分子质量为40.21 kD。该酶的最适温度和最适pH值分别为60 ℃和6。在25～45 ℃及pH 5～9的范围内非常的稳定。在测定条件下测得该酶的Km值为53.79 mmol/L。硫氰化钾对该酶活力基本无影响。尿素、K+、Mn2+、Ca2+、Mg2+、Ba2+、Cu2+对该酶都具有激活作用且浓度至50 mmol/L时酶活力分别被激活至112%、127%、113%、128%、139%、199%、348%,然而十二烷基磺酸钠、抗坏血酸和草酸对该酶有强烈的抑制作用;Zn2+、甲醇、乙醇和异丙醇对该酶有一定的抑制作用。     

不同处理方式对青豆颗粒抑制褐变及品质保持的影响

本研究以青豆颗粒为原料,通过酸处理、热激处理等手段对青豆进行保鲜处理,并考察其对样品的生理变化（丙二醛MDA含量、多酚氧化酶PPO活性、过氧化物酶POD活性、色差、失重率）和品质变化（总糖含量、蛋白质含量、VC含量）的影响,研究0．2％柠檬酸和0．1％抗坏血酸处理对青豆在4℃左右条件下的生理及品质的变化的影响。结果表明,两者均可抑制青豆粒的PPO活性和因蒸腾作用引起的失水,延缓膜脂过氧化产物MDA含量上升、抑制VC含量下降,从而起到延缓青豆衰老、减轻褐变和延长贮藏期的目的。还研究了45℃热水热激处理30、60s对青豆在4℃左右条件下的生理及品质的变化影响。结果表明,对青豆粒进行热激处理可显著降低青豆的PPO活性,抑制MDA含量的上升及VC含量的下降。     

韭菜过氧化物酶的分离纯化及性质

经匀浆、抽提、硫酸铵分级沉淀、CM-Sepharose 离子交换层析、Superdex-200凝胶过滤层析,获得电泳纯的韭菜过氧化物酶(POD)。该酶比活力达到14031.41U/mg,纯化倍数为102.96,回收率为10.85%。该酶分子质量约为28.4kD,最适温度40℃、最适pH值为4.6。该酶在20～40℃以及pH 4.0～8.0有较好的稳定性,在最适条件下测得其Km值为18.15mmol/L。低浓度草酸、Zn2+、Mg2+等对该酶有较强激活作用;甲醇、乙醇、异丙醇、SDS、抗坏血酸(AsA)以及Mn2+、Fe3+等对该酶有较强的抑制作用。     

Exocrine Pancreatic Secretions in Young Pigs Fed Diets Containing Faba Beans (Vicia faba) and Peas (Pisum sativum): Nitrogen,Protein and Enzyme Secretions

Two experiments were carried out to investigate the effect of feeding diets containing faba beans and peas on pancreatic secretions in young pigs fitted with a pancreatic pouch re-entrant cannula. In Experiment 1, eight barrows, with an average initial weight of 8·5 kg, were fed one of two maize starch-based diets formulated to contain 200 g crude protein (CP) kg⁻¹ according to a completely randomised design. In one of the diets, soya bean meal was the sole protein source; in the other diet, soya bean meal and faba beans (cv Fibro; dark-flowering) each supplied 50% of the dietary CP. In Experiment 2, five barrows, with an average initial weight of 18·1 kg, were fed one of two diets according to a two-period change-over design. The diets were formulated to contain 150 g CP kg⁻¹ with peas (cv Ascona or cv Radley) as the sole protein source. In both experiments, the experimental periods consisted of 8 days: 6 days adaptation followed by a 2 day collection of pancreatic juice. The soya bean meal diet and the faba bean diet contained 0.04 and 0.21% tannins (catechin equivalents), respectively. The trypsin inhibitor activities of the Ascona and Radley pea diets were 0·76 and 3·24 mg of trypsin inhibited per gram, respectively. In both experiments, diet did not affect ( P> 0·05) the pancreatic secretions of nitrogen, protein, amylase, lipase and chymotrypsin. In Experiment 1, specific trypsin activity was higher ( P< 0·05) in pancreatic juice from pigs fed the diet containing soya bean meal and faba beans (53700 units litre⁻¹) than for those fed the soya bean meal diet (41200 units litre⁻¹). However, there was no effect ( P> 0·05) when trypsin activity was expressed as total activity (units 24 h⁻¹). It is concluded that the inclu-sion of faba beans and peas in diets for young pigs has only minor effects on exocrine pancreatic secretions.     

Functional properties of protein hydrolysates from pea (Pisum sativum,L) seeds

The aim of this study was to investigate the effects of partial enzymatic hydrolysis on functional properties of two different pea protein isolates obtained from two pea genotypes, Maja and L1. Papain and commercial protease (Streptomyces griseus protease) were used for protein modification. Solubility, emulsifying and foaming properties were estimated at four different pH values (3.0, 5.0, 7.0 and 8.0). Papain increased solubility of L1 pea protein isolate at pH 3.0, 5.0 and 8.0, emulsifying properties and foaming capacity at all pH values. Otherwise, papain increased solubility of Maja pea protein isolate only at pH 8.0. This pea protein isolate modified with both enzymes formed emulsions with improved stability at lower pH (3.0, 5.0). The commercial protease‐prepared pea protein isolates showed generally low solubility and different emulsifying and foaming properties. Proper selection of enzyme, conditions of hydrolysis and genotypes could result in production of pea protein isolates with desirable functional properties.     

The volatiles of off-flavoured unblanched green peas (Pisum sativum)

Volatile extracts of moderately off-flavoured frozen peas, prepared by vacuum sublimation followed by concentration of the sublimate by low temperature vacuum distillation, were examined by gas chromatography, silica gel chromatography and combined gas chromatography–mass spectrometry. The constituents identified included alcohols (29), carbonyls (31), esters (12), hydrocarbons (19), terpenes (6) and 3-alkyl-2-methoxypyrazines (3). Olfactory monitoring of the gas chromatographic column effluent indicated that most of the strong odours were associated with alkanals, alk-2-enals, alka-2,4- and 2,6-dienals, octa-3,5-dien-2-ones, 3-alkyl-2-methoxypyrazines and hexanol. However, no compound which, by itself, could account for the “hay-like” off-flavour of peas was evident. The off-flavour is considered to be complex and composed largely of the more odorous unsaturated carbonyls derived from the enzymic breakdown of the unsaturated pea lipids. The volatiles of pea shells similarly examined were found to contain many of the compounds present in peas.     

蕹菜过氧化物酶的分离纯化及理化性质

新鲜蕹菜经硫酸铵分级沉淀、DEAE-Sepharose离子交换层析和Superdex-200凝胶过滤层析后获得电泳纯的过氧化物酶（peroxidase,POD）,该酶的比活力、回收率、纯化倍数和产率分别为35 972.96 U/mg、12.21%、168.48和211.07 U/g。该酶的亚基分子质量为42.7 kD,最适温度为40 ℃,最适pH值为6,并且在20～50 ℃及pH 5～8的范围内具有良好的稳定性。以不同浓度的H2O2为底物,测得该酶的Km值为18.32 mmol/L。NaCl、尿素（Urea）、Zn2+、Mg2+对该酶都具有较强的激活作用,十二烷基硫酸钠（sodium dodecyl sulfate,SDS）、硫氰化钾（potassium thiocyanate,KSCN）、抗坏血酸（ascorbic acid,AsA）、Ba2+、Mn2+ 、Fe2+、甲醇、乙醇、正丁醇和异丙醇对蕹菜POD活力均有抑制作用,其中抗坏血酸对POD有极强的抑制作用,当浓度为0.01 mol/L时,酶活力接近于0。