柑橘皮中果胶酯酶的生物学特性研究

研究了柑橘皮中的果胶酯酶的生物学特性。用盐析法从新鲜柑橘皮中提取果胶酯酶粗酶液,用pH-stat法测定果胶酯酶的活力。结果表明,该柑橘皮中的果胶酯酶的最适温度在50℃左右,且对热稳定性好,其最适pH在8左右。     

Pectinesterase and Polygalacturonase Activities and Textural Properties of Rubbery Papaya (Carica papaya Linn.)

: Comparisons in color of flesh, pectin composition, pectinesterase (PE), polygalacturonase, cellulase activities, and textural properties of normal green papaya (NGP), rubbery papaya (RP), and normal yellow and ripe papaya (NYRP) were conducted. RP contained about 9.7% pectin with a degree of esterification of 53.1%, while NYRP contained about only 1.2% pectin with a degree of esterification of about 23.4%. PE activity (13.6 unit/g fresh weight) than in RP was significantly lower (18.0 unit/g fresh weight) in NYRP (P < 0.05), whereas polygalacturonase activity (46.9 unit/g fresh weight) in RP was higher (27.0 unit/g FW) than in NYRP. Therefore, in combination with the fact that water extract from RP displayed an inhibitory ratio of 36.0% on papaya PE activity, we suggest the presence of certain substances with strong PE inhibitory activity in RP.     

黑曲霉产果胶酯酶发酵条件的研究

比较了黑曲霉(AS3.350)以有机和无机氮为氮源液态发酵制备果胶酯酶的效果,并对有机氮源的液态发酵条件进行优化。结果表明,以有机氮为氮源的发酵效果优于无机氮,黑曲霉(AS3.350)接种量0.3mL(3×103个孢子),转速90r/min,30℃发酵4d时,果胶酯酶活力高达93.4U/mL培养基。     

Influence of Pectinesterase Inhibitor from Jelly Fig (Ficus awkeotsang Makino) Achenes on Pectinesterases and Cloud Loss of Fruit Juices

ABSTRACT: Citrus and jelly fig achene pectinesterase (PE) (1 U/mL) activity was remarkably inhibited by PE inhibitor (PEI) (2 mg/mL) from jelly fig ( Ficus awkeotsang Makino) achenes, in the absence or presence of 0- to 500-mM salts or 0 to 30% of sugars. Changes in temperature (20 to 40 °C) apparently decreased the activity of citrus PE in PE-PEI reaction mixture. Enzyme-activity curves for jelly fig PE alone and for that in combination with PEI were parallel. Activity of crude PEs (1 U/mL) from tomato, apple, asparagus, and guava was reduced remarkably. Cloud loss of fresh tomato juice, apple juice, and papaya juice was greatly inhibited by PEI (1 mg/mL) during 12-wk storage.     

Kinetic compensation relations for ascorbic acid degradation and pectinesterase inactivation during orange juice pasteurisations

The thermal degradation kinetics of ascorbic acid and the inactivation kinetics of pectinesterase were studied experimentally with pH-adjusted orange juice. No simple trends were observed in variation of the kinetic parameters with pH, but both kinetic functions agreed with kinetic compensation relations. An isokinetic temperature was observed for ascorbic acid degradation at pH 2.5, 3.0, and 3.5 implying that the same degradation mechanism was valid at these pH values. A large deviation at pH 4.0 from this isokinetic reaction rate implied that the degradation mechanism was different at this pH. There was no isokinetic temperature for pectinesterase inactivation reactions, indicating that pectinesterase was inactivated by different mechanisms at different pH values. The variation of the inactivation mechanism of pectinesterase with pH was attributed to its more complex molecular structure.     

一种制备高纯果胶酯酶的方法研究

采用温度控制结合抑制剂的方法对高纯果胶酯酶酶制剂的制备方法进行研究。通过正交试验,得到制备高纯果胶酯酶制剂的最优工艺条件是:温度55℃,七水合硫酸亚铁(FeSO.47H2O)浓度1 mol/L,时间10 min。在此条件下,果胶酯酶酶活残余为80.57%,而聚半乳糖醛酸酶的活力仅仅残留了8.29%。     

Pectinesterase and polygalacturonase in changes of pectic matter in olives (cv. Hojiblanca) intended for milling

Virgin olive oil is a highly valued product, and it is important to optimize extraction yield. The pectic composition and the related enzymatic activities, present in the raw material, are variables that may affect that process. The pectinolytic activities producing modifications in the pectic matter of olive fruits (variety Hojiblanca) during ripening and the associated changes in texture were studied. Pectinesterase (PE) activity increased with ripeness until reaching a peak when anthocyanin synthesis in the fruit became marked (turning color stage). From then on, it decreased. In contrast, polygalacturonase (PG) activity in the ripe-green fruit decreased sharply when anthocyanin formation began (small reddish spots stage) and then increased, reaching a maximum in the ripe-black fruit. Parallel changes were noted in the texture and pectic content of the olives, related to endo- and exo-PG enzymatic activities, together with a decrease in the degree of esterification of the pectic matter, which could be associated with PE action. The distribution of the pectic fractions in the raw material and the changes in them during the olive oil extraction process showed the role of PE and PG in the fruits that was related to the yield of extracted oil.     

气调包装对草莓货架期延长保鲜内在品质的影响

植物组织或器官在衰老过程中常伴随细胞膜结构的破坏,导致组织结构和细胞区域化的丧失。研究经过气调包装(MAP)处理后草莓超微结构的变化,结果表明经过MAP处理能较好地维持草莓细胞形状。果胶酯酶(PE)活性是影响草莓货架期的内在因素之一。采用NaCl盐析法得到了草莓果胶酯酶粗提液,对草莓果胶酯酶的特性进行了探索。试验结果表明,氯化钙溶液对果胶酯酶的活性影响很大,植酸同样可抑制果胶酯酶的活性,以0.05%效果最好。     

Influence of addition of insoluble solids,different yeast strains and pectinesterase enzyme on the quality of apple wine

Rate of fermentation and physico‐chemical characteristics of apple wines, owing to the addition of different yeast strains, insoluble solids and pectinesterase enzyme, were examined. The highest rates of fermentation and ethanol production were found in the wine fermented by yeast strain UCD 505, while strain UCD 595 gave the smallest amount of methanol. The addition of insoluble solids to the apple juice significantly increased the levels of methanol, vitamin C, amyl alcohol, total volatiles, rate of fermentation, tannins, colour units, Mn and Zn. Addition of insoluble solids decreased pH, titrable acidity, ethanol, total sugars, total esters, and K, Mg, Ca, Cu and Fe content of the wine. Addition of pectinesterase enzyme significantly increased all the parameters examined except for pH, vitamin C, total esters, Mn and Mg content. Application of cluster analysis to the results of rate of fermentation, reducing sugars, volatile acidity and ethanol showed that the influence of the yeast strains was more than the influence of insoluble solids or pectinesterase enzyme addition. Consideration of more parameters showed that there was a clear interaction between the yeast strain, insoluble solids and the pectinesterase enzyme. Addition of insoluble solids to the must led to the production of some undesirable quality characteristics. In contrast, specific yeast strains and enzyme addition improved various physico‐chemical characteristics of the wine. Pre‐settled or clarified juice was preferred to produce a quality apple wine. Copyright © 2013 The Institute of Brewing & Distilling     

Inorganic Cations and Polyamines Moderate Pectinesterase Activity

Inorganic and organic cations influenced pectinesterase (PE) activity and solubilization from Marsh grapefruit pulp. Activity increased to 281%, 183%, and 130% with lead acetate (6.8 mM), ferric chloride (0.2 mM), and calcium chloride (20 mM), respectively. The polyamines, putrescine, spermidine, and spermine had negligible stimulating effect. All cations tested inhibited PE activity at higher concentrations. Solubilization of total PE was decreased and thermostable PE (TS-PE) was not affected by polyamines. There was a progressive decline in total PE activity above 1.6 mM spermidine, 7.6 mM putrescine and 20.0 mM spermine. Loss of activity upon solubilization suggests that the TL-PE-pectate complex stabilized TL-PE. No change in TS-PE activity suggests that it may be bound with greater affinity, physically entrapped, or non-electrostatically bound.