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Enzymatic Browning (enzymatic + browning)
Selected AbstractsInhibition kinetic and mechanism of polyphenol oxidase from various sources by diethyldithiocarbamic acidINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 7 2008Serap Do Summary Inhibition kinetics and mechanism of polyphenol oxidases (PPO) partially purified from various sources such as Thymbra spicata L. var. spicata and Ocimum basilicum L., and of mushroom PPO bought from Sigma by diethyldithiocarbamic acid have been described using catechol, 4-methylcatechol and pyrogallol as substrates. The inhibition type was competitive for O. basilicum L. PPO using catechol and 4-methylcatechol as substrates, for mushroom PPO using catechol, 4-methylcatechol and pyrogallol as substrates, and for T. spicata L. var. spicata PPO using 4-methylcatechol as a substrate; uncompetitive inhibition for T. spicata L. var. spicata PPO using pyrogallol as a substrate; and non-competitive inhibition for O. basilicum L. and T. spicata L. var. spicata PPO using pyrogallol and catechol as substrates, respectively. The inhibition effect of diethyldithiocarbamic acid on enzymatic browning varied greatly from one phenol to another and from one enzyme to another. Hence, no general rule can easily be established with regard to the type of inhibition observed. [source] Prevention of enzymatic browning of apple cylinders using different solutionsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 12 2007Charles Tortoe Summary Inhibition of enzymatic browning and decay on cut surfaces of Golden Delicious apple using ascorbic acid, cysteine, sodium chloride, calcium chloride, citric acid and sodium ascorbate alone or in combinations was investigated at 4 and 10 °C for a storage period of 0, 7 and 14 days, in an attempt to find the most effective treatment. Apple segments immersed in ascorbic acid and citric acid alone showed visual traces of browning after 7 days storage at 4 °C. After 14 days storage, only ascorbic acid and ascorbic acid plus sodium chloride had moderate browning, while all other treatments were severely affected. However, at 10 °C, only ascorbic acid was effective in reducing the level of browning, although its effect was minimal after 14 days storage. Browning was more severe at 10 °C than 4 °C in all solutions. The browning measurement (a* value) became increasingly positive from 7- to 14-day storage. Microbial decay was absent in all treatments within 7 days at 4 and 10 °C. However, three test solutions showed microbial decay after 14 days storage at 10 °C in addition to the control solution, which showed decay at both 4 and 10 °C storage temperatures. [source] CHARACTERIZATION OF POLYPHENOL OXIDASE FROM ROOSTER POTATO (SOLANUM TUBEROSUM CV ROOSTER)JOURNAL OF FOOD BIOCHEMISTRY, Issue 1 2010D. NI EIDHIN ABSTRACT The isolation and purification of polyphenol oxidase from potatoes (Solanum tuberosum cv. Rooster) is described. A 64-fold purified preparation has been obtained with 10% yield by a procedure involving (NH4)2SO4 precipitation, phenyl sepharose chromatography, ion exchange chromatography and hydroxyapatite chromatography. The partially purified enzyme has both cresolase and catecholase activity. Activity was lower toward monophenols than diphenols. Enzyme activity was optimal at pH 6.0,6.5 and at 30C. Greater than 50% activity was retained during storage for 72 h at pH 6.0,7.5. Residual activity was greater than 50% after incubation at 20C for 72 h, 30C for 48 h, 40C for 24 h, 50C for 2 h and 60C for 15 min. The most effective inhibitors tested were sodium metabisulfite and ascorbic acid. Sodium dodecyl sulphate appeared to activate the enzyme. The enzyme was capable of cross-linking casein but did not increase gel-strengths in acidified milk gels. PRACTICAL APPLICATIONS Rooster is the most important potato cultivar grown in Ireland and data on its isolation and characterization has not been reported previously. This work describes a method to isolate polyphenol oxidase and characterization of the enzyme. Information on characterization of the enzyme could be valuable in relation to control of enzymatic browning during current processing and in minimum processing. There is potential for use of the enzyme in the emerging cross-linking area, as the results show some success and there may be potential of more cross-linking as the field develops and as interest in natural methods of cross-linking for food texture grows. This could lead to an important use for potato waste. Food product applications are given. [source] POLYPHENOLOXIDASE ACTIVITY OF MINIMALLY PROCESSED ,JONAGORED' APPLES (MALUS DOMESTICA)JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 1 2005A.M.C.N. ROCHA ABSTRACT The influence of three chemical dips using ascorbic acid (AA), citric acid (CA) and calcium chloride (CC) on the polyphenoloxidase (PPO) activity and on the total phenolic content of minimally processed (MP) apple (Malus domestica, cv. Jonagored) during cold storage was evaluated and a potential relationship with enzymatic browning was investigated. An ascorbic acid dip (42.6 mM) of 5 min duration was the most efficient chemical treatment in reducing the PPO activity of apple cubes. A 92% inhibition was achieved after 7 days of storage at 4C. All treatments were advantageous in comparison to the control in reducing color changes. Color changes, determined by absorbance at 420 nm (soluble pigments) and lightness (L) (insoluble pigments) of apple cubes treated with ascorbic acid were correlated with total phenolic content. No correlation was observed between PPO activity and tristimulus color parameters, browning index or total phenolic content of AA-treated apple cubes. [source] EFFECT OF OXYGEN CONCENTRATION ON THE BIOCHEMICAL AND CHEMICAL CHANGES OF STORED LONGAN FRUITJOURNAL OF FOOD QUALITY, Issue 1 2009G. CHENG ABSTRACT Longan fruits were stored for 6 days in atmosphere of 5, 21 (air) or 60% O2 (balance N2) at 28C and 90,95% relative humidity to examine effects of low and high O2 concentration on enzymatic browning and quality attributes of the fruit. Changes in pericarp browning, pulp breakdown, disease development, total phenol content, activities of phenol metabolism-associated enzymes, relative leakage rate, ,,, -diphenyl- , -picrylhydrazy (DPPH) radical scavenging activity, and contents of total soluble solids, titratable acidity and ascorbic acid were evaluated. Storage of fruit in a 5% O2 atmosphere markedly delayed pericarp browning in association with maintenance of high total phenolic content and reduced activities of polyphenol oxidase (PPO), peroxidase (POD) and phenylalanine ammonia lyase. Moreover, the fruit stored in a 5% O2 atmosphere exhibited a lower relative leakage rate and higher DPPH radical scavenging activity than fruit stored in air. This presumably was beneficial in maintaining compartmentation of enzymes and substrates, and thus, reducing pericarp browning. Pulp breakdown and disease development were also reduced by exposure to a 5% oxygenatmosphere. On the contrary, exposure of longan fruit to a 60% O2 atmosphere accelerated pericarp browning, pulp breakdown and decay development. PPO and POD activities and relative leakage rate were similar for control and 60% O2 -treated fruit after 4 and 6 days of storage. Furthermore, treatment with 60% O2 significantly decreased the phenolic content and DPPH scavenging activity of fruit. In addition, exposure to 5 or 60% O2 resulted in a higher level of total soluble solids, but a lower level of ascorbic acid of longan fruit flesh. In conclusion, exposure to a 5% O2 atmosphere showed great potential to reduce pericarp browning and extend shelf life of longan fruit. PRACTICAL APPLICATIONS Pericarp browning and pulp breakdown are the major causes of deterioration in postharvest longan. Conventional controlled atmosphere with low O2 and high CO2 is effective in maintaining quality and extending shelf life of fruits and vegetables, including inhibition of tissue browning. In this study, 5%-controlled atmosphere reduced significantly pericarp browning, pulp breakdown and rot development. It could potentially be useful as a postharvest technology of longan fruit for reducing or replacing the use of chemicals such as SO2 and fungicides, but it requires further investigation. [source] Inhibition of Browning on Fresh-cut Pear Wedges by Natural CompoundsJOURNAL OF FOOD SCIENCE, Issue 3 2006Gemma Oms-Oliu ABSTRACT: Mechanical operations such as peeling and cutting during minimal processing involve enzymatic browning of fruit tissue. The objective of this work was to evaluate the individual and combined effects of N-acetyl-L-cysteine, reduced glutathione, ascorbic acid, and 4-hexylresorcinol to control pear browning. Browning of fresh-cut pears was prevented by a minimum concentration of 0.75% N-acetyl-L-cysteine up to 28 d at 4°C. Reduced glutathione treatments were also effective along the storage time although browning was observed after 21 d of storage with a dip of 0.75% reduced glutathione. However, ascorbic acid or 4-hexylresorcinol treatments did not seem to completely prevent browning of pear wedges throughout the storage period. An enhanced antibrowning effect was observed when combining both N-acetyl-L-cysteine and reduced glutathione, considering hue angle as color change index. Thus, hue angle reached maximum levels at 1.5% N-acetyl-L-cysteine (NAC) or 1.5% glutathione (GSH) and 1% NAC with 1% GSH for 28 d. Besides, N-acetyl-L-cysteine, reduced glutathione and 4-hexylresorcinol completely inhibited polyphenol oxidase activity as well as browning inhibitors slightly reduced firmness of fresh-cut pears. [source] Modelling the effect of superatmospheric oxygen concentrations on in vitro mushroom PPO activity,JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 14 2006Perla A Gómez Abstract The kinetics of polyphenol oxidase (PPO, EC 1.14.18.1) with respect to oxygen concentrations from 5 to 100% using chlorogenic acid (CGA) as substrate was examined. In vitro mushroom PPO activity was determined by measuring the consumption of oxygen during the oxidation reaction. A differential Michaelis,Menten model was fitted to the obtained total depletion curves. The product concentration as well as the concentration of oxygen had a clear inhibitory effect on the reaction rate. However, the inhibitory effect of oxygen was more evident at low product concentration. A linear mixed inhibition model that considered both the product (oxidised CGA) and oxygen as inhibitors was developed. A model with the product as a competitive inhibitor and oxygen as an uncompetitive inhibitor was the most appropriate to explain the reaction kinetics. The values of the inhibition constants calculated from the model were 0.0032 mmol L,1 for Km (Michaelis,Menten constant related to oxygen), 0.023 mmol L,1 for Kmc (constant for competitive inhibition due to the product), 1.630 mmol L,1 for Kmu (constant for uncompetitive inhibition due to oxygen) and 1.77 × 10,4 mmol L,1 s,1 for Vmax (maximum reaction rate). The results indicate that superatmospheric oxygen concentrations could be effective in preventing enzymatic browning by PPO. Copyright © 2006 Society of Chemical Industry [source] Study of the effect of ripening stages and climatic conditions on the physicochemical and sensorial parameters of two varieties of Vitis vinifera L. by principal component analysis: influence on enzymatic browningJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 4 2006M Serrano-Megías Abstract The present paper describes the effects of maturation on the physicochemical, biochemical and color components of Napoleon and Dominga grape varieties, and on any differences between them. Climatic conditions were taken into account to explain the results obtained. Protein levels increased during ripening and were correlated with pH. Polyphenoloxidase activity was affected by climatic conditions (rainfall) and increased to a greater degree in Dominga than in Napoleon. Taste tests were conducted to determine the contribution of physicochemical and biochemical parameters to the sensorial properties of the grapes. Principal components analysis showed that parameters were correlated in different ways during the ripening period in Napoleon and Dominga varieties. In Dominga AE were correlated to the b parameter and in Napoleon to the L parameter. Copyright © 2005 Society of Chemical Industry [source] A response surface methodology approach to optimise pretreatments to prevent enzymatic browning in potato (Solanum tuberosum L) cubesJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 1 2002C Reyes-Moreno Abstract The objective of this work was to find the best combinations of ascorbic acid concentration/soaking time (Pretreatment 1), 4-hexylresorcinol concentration/soaking time (Pretreatment 2) and ascorbic acid concentration,4-hexylresorcinol concentration/soaking time (Pretreatment 3) to prevent the development of enzymatic browning in raw potato cubes (10,mm,×,10,mm,×,10,mm). Potato variety Alpha was used as study model because of its low susceptibility to enzymatic browning. Response surface methodology was applied in all pretreatments on two response variables (Hunter L value and total colour difference) to find the best conditions for carrying out the pretreatments. The various pretreatments had variation levels for ascorbic acid (AA) concentration (1 and 3) and 4-hexylresorcinol (4HR) concentration (2 and 3) of 1,4 and 0.04,0.20,g,l,1 respectively; in all pretreatments the variation level for soaking time was 3,6,h. A central composite experimental design with two factors at five levels was used. Predictive models for Hunter L value and total colour difference were developed as a function of process or independent variables. The optimisation technique was applied to obtain maximum Hunter L values and minimum values of total colour difference. Surface superposition of these variables allowed identification of the best combinations of process variables for each pretreatment as (1) 2.9,g,l,1 AA/4.8,h, (2) 0.04,g,l,1 4HR/2.6,h and (3) 2.42,g,l,1 AA,0.15,g,l,1 4HR/5.41,h. © 2001 Society of Chemical Industry [source] | ||||||||||