葡萄糖氧化酶抑制苹果汁褐变工艺的研究

以苹果果汁为原料,研究葡萄糖氧化酶对苹果汁在加工贮藏过程中主要褐变因素的影响,在单因素试验基础上,利用Box-Behnken响应面试验设计优化葡萄糖氧化酶抑制苹果汁褐变的最佳工艺条件为:酶添加量0.4%,作用温度37℃,作用时间35min,所得苹果汁褐变指数为0.154。此工艺条件下,葡萄糖氧化酶抑制苹果果汁褐变效果最佳。     

Studies on enzymic browning of potatoes (Solanum tuberosum)

Summary Using analytical data from the literature the tyrosine turnover was calculated by a method published previously by us for 72 potato samples with different rates of browning. The samples included 9 varieties grown at three locations in 1969, which were analysed after harvest and after different times of storage at three temperatures. For 58 samples (81%) this calculation led to the same classification of the varieties as did visual observation of the rate of discolouration. It is concluded that enzymic browning of potatoes is correlated rather with tyrosine turnover, which depends on the concentrations of phenol oxidase, tyrosine, chlorogenic acid, and ascorbic acid, than with any single parameter.

---

Untersuchungen zur enzymatischen Bräunung bei Kartoffeln (Solanum tuberosum)IV. Beziehung zwischen Tyrosinumsatz und Bräunung

Zusammenfassung Aus Analysendaten der Literatur wurde für 72 unterschiedlich bräunende Kartoffelproben der Tyrosinumsatz nach einer von uns kürzlich veröffentlichten Methode berechnet. Die Proben beinhalten 9 Sorten aus 3 Standorten im Jahr 1969, die nach der Ernte and nach verschiedenen Lagerzeiten bei 3 verschiedenen Temperaturen analysiert wurden. Die Berechnung des Tyrosinumsatzes führte bei 58 Proben (81%) zur gleichen Klassifizierung der Sorten wie die sensorische Beurteilung der Bräunung. Es wird gefolgert, daß die enzymatische Bräunung bei Kartoffeln eher mit dem Tyrosinumsatz, der von den Konzentrationen an Phenoloxydase, Tyrosin, Chlorogensäure und Ascorbinsäure abhängig ist, als mit einem einzelnen Parameter korreliert ist.

---

---

Dedicated to Prof. Dr. L. Acker on his 65 ^th birthday     

Inhibition of browning by antibrowning agents and phenolic acids or cinnamic acid in the glucose–lysine model

The effects of antibrowning agents and phenolic acids or cinnamic acid on the inhibition of browning were investigated with a glucose–lysine model. Six antibrowning agents (cysteine, glutathione, sodium sulfite, pentasodium tripolyphosphate, citric acid and oxalic acid) and four phenolic acids (ferulic, hydroxybenzoic, syringic and vanillic acids) were used. In order to investigate the antibrowning capacity of these agents, model solutions containing glucose, lysine and an antibrowning agent were heated at 50 °C in the presence of FeCl₂, before being stored in nitrogen or air at 4 °C or 30 °C. Browning was accelerated to some degree during storage in air at 30 °C. In the case of storage at 4 °C, however, no browning was detected in nitrogen after four weeks. Citric acid was the most efficient antibrowning agent during storage in air at 30 °C and inhibited browning to 36% after four weeks. However, its antibrowning capacity was increased by 8–15% in the presence of any of the phenolic acids or cinnamic acid, essentially independently of concentration in the range 10 µM to 10 mM or the type of phenolic acid. Copyright © 2005 Society of Chemical Industry     

Studies on enzymic browning of potatoes (Solanum tuberosum). I. Phenoloxidases and phenolic compounds from different varieties (author's transl)]

31 samples of potato varieties with slow, medium and fast rates of browning were studies. Characteristic enzyme patterns were obtained from polyacrylamide gel electrophoresic of the phenoloxidases of varieties with different discolouration rates. The differences lie mainly in the intensities of the enzyme bands. The qualitative determinaiton of the phenols showed no significant differences. Tyrosine, chlorogenic acid and caffeic acid produce coloured oxidation products; the characteristic colour gradations of in vivo browning were only observed in the presence of tyrosine. It is concluded that the same reactions take place during the discolouration of all the varieties.     

Polyphenol oxidase activity,phenolic acid composition and browning in cashew apple (Anacardium occidentale, L.) after processing

This study describes the extraction and characterisation of cashew apple polyphenol oxidase (PPO) and the effect of wounding on cashew apple phenolic acid composition, PPO activity and fruit browning. Purification factor was 59 at 95% (NH₄)₂SO₄ saturation. For PPO activity, the optimal substrate was catechol and the optimum pH was 6.5. PPO K_m and V_max values were 18.8 mM and 13.6 U min⁻¹ ml⁻¹, respectively. Ascorbic acid, citric acid, sodium sulphite and sodium metabisulphite decreased PPO activity, while sodium chloride increased PPO activity. Wounding at 2 °C and 27 °C for 24 h increased PPO activity but storage at 40 °C reduced PPO activity. Gallic acid, protocatechuic acid and cinnamic acid (free and conjugate) were identified in cashew apple juice. Cutting and subsequent storage at 40 °C hydrolysed cinnamic acid. 5-Hydroxymethylfurfural content in cashew apple juice increased after injury and storage at higher temperatures, indicating non-enzymatic browning.     

Inhibition of polyphenol oxidase and the browning control of litchi fruit by glutathione and citric acid

Polyphenol oxidase (PPO, EC 1.10.3.2) from litchi peel was partially purified by ammonium sulfate fractionation and gel filtration, and a 16-fold purification of PPO achieved. The use of 10 mmol litre⁻¹ glutathione and 100 mmol litre⁻¹ citric acid was found to give good control of the browning of litchi fruit and 80–85% inhibition of PPO observed. Application of glutathione in combination with citric acid is recommended as a way of slowing the browning of litchi fruit.     

Studies on enzymic browning of potatoes (Solanum tuberosum). II. The quantitative relationship between browning and its causative factors (author's transl)]

Ten potato varieties, with different rates of browning, were analyzed quantitatively for phenoloxidase, tyrosine, chlorogenic acid, caffeic acid, and for reducing substances (ascorbic acid). The rate of tyrosine turnover was calculated from the data. The fact that the further reactions of the primary oxidation products leading to browning only take place after complete oxidation of the reducing substances, was taken into account. This leads to the same classification of the varieties as does visual observation of the rate of discolouration. Thus a clear relationship between browning and potato constituents is demonstrated.     

The influence of some pesticides on the quality of apples. I. Enzymatic browning reactions

Zusammenfassung In Äpfeln, welche mit den Pesticiden Melprex 65 W und/oder Anthio 25 behandelt wurden, und weiterhin in nicht behandelten Früchten (Kontrolle) wurden bedeutende Mengen von Substraten der Polyphenoloxidasen festgestellt. In den Proben wurden unterschiedliche Mengen von o-Diphenolen und phenolischen Säuren gefunden. Eine signifikant niedrigere Menge dieser Stoffe wurde in den mit Melprex 65 W behandelten Früchten nachgewiesen. Die Aktivität der Polyphenoloxidasen in dieser Probe ist fast identisch mit der Kontrolle. In den mit Anthio 25 behandelten Früchten beobachtete man ein etwas geringeres Braunwerden. Interessant ist die Feststellung, daß Dodine, der aktive Bestandteil von Melprex 65 W, die Bildung von Farbprodukten bei den Reaktionen der enzymatischen Bräunung beeinflußt.

---

The influence of some pesticides on the quality of apples. I. Enzymatic browning reactions

Summary The contents of some significant substrates of apple polyphenol oxidase were determined either in fruit treated with Melprex 65 W and/or Anthio 25 and in untreated fruit. Some differences were found in the concentrations of o-Dihydroxyphenols and phenolic acids. The significantly lower content of these substances was checked in apples treated with Melprex 65 W. The activity of polyphenol oxidase in this sample was nearly the same as that in a control. A slightly lower rate of browning was observed in apples treated with Anthio 25. It was proved that dodine (active ingredient of Melprex 65 W) participates in the formation of coloured products originating during enzymatic browning reactions.

     

鸡腿菇的酶促褐变机理及其抑制研究

采用SPSS软件分析鸡腿菇贮藏过程中褐变与多酚氧化酶(PPO)、过氧化物酶(POD)活性变化的关系.用抗坏血酸(Vc)、亚硫酸钠和柠檬酸分别处理鸡腿菇,试图找到减轻鸡腿菇褐变的方法.结果表明:鸡腿菇在贮藏过程中褐变度逐渐增大,POD活性呈先上升后下降的趋势,其褐变度与PPO活性显著相关,均趋于上升,PPO活性的变化是引起鸡腿菇酶促褐变的主要原因;Vc、亚硫酸钠和柠檬酸三种处理均可不同程度地减轻鸡腿菇的褐变度,其中0.15-0.2mmol/L的柠檬酸处理效果最好,其次是亚硫酸钠和Vc.     

Inhibition by carboxylic acids of an o-diphenol oxidase from Prunus avium fruits

Aromatic carboxylic acids strongly inhibited 4-methylcatechol oxidation by an o-diphenol oxidase extracted from sweet cherry fruits (Prunus avium). Esterification of the acids decreased their inhibitory strength. Inhibitors containing the benzene nucleus showed a greater effectiveness than the corresponding aliphatic and heterocyclic compounds (except 2-naphthalenecarboxylic acid). Similar inhibitory effects were observed by replacing the benzene ring with a highly unsaturated open chain. The inhibitory properties of benzoic acid, cinnamic acid, p-coumaric acid and 3,4-dihydroxybenzoic acid were investigated. It is proposed that the catalytic and inhibitory sites are close together in the enzyme molecule.     

Inhibition of loquat enzymatic browning by sulfhydryl compounds

The effectiveness of a series of sulfhydryl compounds in inhibiting polyphenoloxidase (PPO) activity in a model system (chlorogenic acid solution) and in loquat juices was evaluated. Application of different concentrations of sulfhydryl compounds to chlorogenic acid solution and fresh loquat juice showed that l-cysteine appeared to be an effective browning inhibitor. The required concentration of l-cysteine for 90% browning inhibition depended on loquat cultivars, and ranged from 0.6 mM for “Nagasaki” to 2.0 mM for “Yukawa” or “Toi”. The difference may be due to the concentration of endogenous phenolic compounds inherent in each cultivar. The results from oxidized product analysis by loquat PPO implied that the mechanism of browning inhibition by thiols involved the formation of a thiol-conjugated reaction product.     

Inhibition of polyphenol oxidase and peroxidase activities on fresh-cut apple by simultaneous treatment of ultrasound and ascorbic acid

The effects of ultrasound and ascorbic acid on activity changes of polyphenol oxidase and peroxidase, of fresh-cut apple during storage, were investigated. The combined treatment of ultrasound and ascorbic acid inactivated monophenolase, diphenolase, and peroxidase, whilst the individual treatment of ultrasound or ascorbic acid had inverse and limited inhibitory effect on the enzymes. The main protein bands had a molecular weight of approximately 63 kDa. A diffuse band, lacking the electrophoretic mobility of proteins, was observed after combined treatment. This investigation revealed that simultaneous treatment with ultrasound and ascorbic acid had synergistic inhibitory effects on several enzymes related to enzymatic browning.     

Inhibition of dipeptidyl peptidase IV and xanthine oxidase by amino acids and dipeptides

Xanthine oxidase (XO) and dipeptidyl peptidase IV (DPP-IV) inhibition by amino acids and dipeptides was studied. Trp and Trp-containing dipeptides (Arg-Trp, Trp-Val, Val-Trp, Lys-Trp and Ile-Trp) inhibited XO. Three amino acids (Met, Leu and Trp) and eight dipeptides (Phe-Leu, Trp-Val, His-Leu, Glu-Lys, Ala-Leu, Val-Ala, Ser-Leu and Gly-Leu) inhibited DPP-IV. Trp and Trp-Val were multifunctional inhibitors of XO and DPP-IV. Lineweaver and Burk analysis showed that Trp was a non-competitive inhibitor of XO and a competitive inhibitor of DPP-IV. Molecular docking with Autodock Vina was used to better understand the interaction of the peptides with the active site of the enzyme. Because of the non-competitive inhibition observed, docking of Trp-Val to the secondary binding sites of XO and DPP-IV is required. Trp-Val was predicted to be intestinally neutral (between 25% and 75% peptide remaining after 60 min simulated intestinal digestion). These results are of significance for the reduction of reactive oxygen species (ROS) and the increase of the half-life of incretins by food-derived peptides.     

浓缩苹果汁生产中控制褐变的研究

对控制苹果浓缩汁生产过程中的褐变进行了研究,结果表明:维生素C和柠檬酸混合使用对PPO褐变抑制作用增强,当果浆的流速控制在8t/h￣9t/h,温度控制在85℃￣90℃时,果汁吸光度降低0.065;采用吸附柱法对果汁进行脱色的最佳工艺条件为真空度1.33×104 Pa;树脂高度36cm,经脱色后果汁的体积(V)与该体积流出液的吸光度(A)之间的关系为:A=0.158+0.255X-0.066X2,X∈[0,1.8L]。     

O-dihydroxyphenoloxidase action on natural polyhydric phenolics and enzymic browning of edible yams

Ten cultivars of five edible yam species were examined for o-dihydroxyphenoloxidase (o-DPOase) activity against yam extracts containing phenolic compounds, and for their propensity to brown when cut slices are exposed to air. (+)-Catechin levels in Dioscorea cayenensis (260 mg kg^?1) and D. bulbifera (240 mg kg^?1) were similar to those in D. dumetorum (270 mg kg^?1), but the latter contained less o-DPOase and showed less tendency to browning. D. alata contained more (+)-catechin than other yams, and one cultivar with a higher (+)-catechin content (660 mg kg^?1) showed more browning than another cultivar containing 430 mg kg^?1 (+)-catechin. Five cultivars of D. rotundata showed less tendency to brown, and had lower (+)-catechin content (90–190 mg kg^?1) than the other yams examined, but showed marked variation in o-DPOase activity. o-DPOase activity, assayed by recording the rate of oxygen consumption, varied between 75 units (1 unit=μmol O₂ consumed min^?1 100 g^?1 fresh yam tissue) in D. dumetorum and 2380 units in one D. rotundata cultivar when a crude extract of phenolic compounds diluted to contain 10 mM (+)-catechin was used as substrate and from 60 to 3480 units for these same two enzyme extracts when assayed using crude extracts of phenolic compounds (also adjusted to contain 10 mM (+)-catechin) prepared from the same yam as the enzyme extract. However, in general, the o-DPOase activities recorded using the D. alata extract showed little correlation with the activity when the phenolic extract was prepared from the same yam as the enzyme extract. Incubation of crude extracts containing phenolics with crude extracts of o-DPOase at 20°C for 24 h resulted in a decrease in the quantity of (+)-catechin estimated by h.p.l.c. Cyanidin released by hydrolysis with HCl under mild conditions was also measured. The level in D. alata was sufficiently high to account for ‘pinking’ when this species is boiled. It is concluded that the o-DPOase-catalysed oxidation of (+)-catechin is largely responsible for the browning of yams. The possible influence of other factors, including the reducing agent ascorbic acid in moderating the rate and extent of browning observed, is discussed.     

混浊苹果汁加工过程中的酶促褐变及其防止的研究

将几种可用于食品的防褐变剂在苹果破碎时加入,考察了它们对苹果浆和苹果鲜榨汁的防褐变效果及它们之间的协同作用。半胱氨酸、抗坏血酸、曲酸、氯化钠和氯化钙都是较好的防褐变剂。在所测试条件下,抗褐变的能力（褐变抑制率）为:0.1％的抗坏血酸>0.1％的偏重亚硫酸钠>0.1％的曲酸>0.1％的氯化钙>0.005％半胱氨酸>0.1％氯化钠。它们抗褐变能力都表现为浓度依赖型,特别是抗坏血酸。柠檬酸在所测试条件下没有抗褐变效果。0.044％NaCl+0.0125％Vc的组合较经济且可使果汁40min不变色。果浆脱气可减缓其褐变;减小果汁及果浆与空气的接触面也可防止褐变。      

Inhibition of enzymatic browning in foods and beverages.

Enzymatic browning is a major factor contributing to quality loss in foods and beverages. Sulfiting agents are used commonly to control browning; however, several negative attributes associated with sulfites have created the need for functional alternatives. Recent advances in the development of nonsulfite inhibitors of enzymatic browning are reviewed. The review focuses on compositions that are of practical relevance to food use.