Isolation of tyrosinase inhibitors from Artocarpus heterophyllus and use of its extract as antibrowning agent

A new furanoflavone, 7-(2,4-dihydroxyphenyl)-4-hydroxy-2-(2-hydroxy propan-2-yl)-2, 3-dihydrofuro(3, 2-g)chromen-5-one (artocarpfuranol, 1), together with 14 known compounds, dihydromorin (2), steppogenin (3), norartocarpetin (4), artocarpanone (5), artocarpesin (6), artocarpin (7), cycloartocarpin (8), cycloartocarpesin (9), artocarpetin (10), brosimone I (11), cudraflavone B (12), carpachromene (13), isoartocarpesin (14), and cyanomaclurin (15) were isolated from the wood of Artocarpus heterophyllus. Their structures were identified by interpretation of MS,( 1)H-NMR,( 13)C-NMR, HMQC, and HMBC spectroscopic data. Among them, compounds 1-6 and 14 showed strong mushroom tyrosinase inhibitory activity with IC(50) values lower than 50 microM, more potent than kojic acid (IC(50) = 71.6 microM), a well-known tyrosinase inhibitor. In addition, extract of A. heterophyllus was evaluated for its antibrowning effect on fresh-cut apple slices. It was discovered that fresh-cut apple slices treated by dipping in solution of 0.03 or 0.05% of A. heterophyllus extract with 0.5% ascorbic acid did not undergo any substantial browning reaction after storage at room temperature for 24 h. The antibrowning effect was significantly better than samples treated with the extract (0.03 or 0.05%) or ascorbic acid (0.5%) alone. The results provide preliminary evidence supporting the potential of this natural extract as antibrowning agent in food systems.     

曲酸、抗坏血酸及柠檬酸对鲜切苹果褐变的影响

以鲜切苹果为试材,分别用曲酸、抗坏血酸和柠檬酸浸泡3 min,于4℃存放9 d,对鲜切苹果的硬度、色泽、总酚、可溶性醌、多酚氧化酶活性、维生素C等指标进行分析。结果表明,3种有机酸对鲜切苹果的硬度和多酚氧化酶的影响差异不显著(P>0.05),而对褐变、总酚和维生素C影响差异显著(P<0.05)。综合来看,3种有机酸均对鲜切苹果褐变都有抑制效果,而曲酸明显优于柠檬酸和抗坏血酸,说明曲酸是一种潜在的鲜切苹果保鲜和护色剂。     

Machine Vision Analysis of Antibrowning Potency for Oxalic Acid: A Comparative Investigation on Banana and Apple

ABSTRACT: Relative antibrowning potency of oxalic acid on banana and apple slices was investigated using a machine vision system. Degree of browning on fresh-cut surfaces was evaluated visually and quantitatively by observing changes of CIE L * values and evaluating temporal changes in color spectra based on experimental variables, oxalic acid concentration, and storage time. Browning inhibition was most prominent on banana and apple slices treated with oxalic acid solutions at concentrations of 60 and 5 m M , respectively. Oxalic acid was a more potent antibrowning agent compared with other structurally related acids. Average residual oxalic acid levels in the tissues for an effective antibrowning activity were measured.     

Thiol containing compounds as controlling agents of enzymatic browning in some apple products

A comparative study concerning the inhibition of the enzymatic browning in Red delicious apple slices and pulp stored for 24 h at 4, 25, and 35 °C was carried out between the thiol containing compounds; cysteine, glutathione and Maillard reaction products (MRPs) derived by heating aqueous solutions containing cysteine with glucose or ribose (Cys/G or Cys/R) and those commercially applied such as: sodium metabisulfite, ascorbic acid and 4-hexyl resorcinol. The efficiency of all antibrowning agents was followed in terms of absorbance and colour measurements. The obtained results confirmed the presence of a proportional relation between the concentration of antibrowning agents and their inhibitory effect, whereas the increase in storage temperatures showed an opposite trend. The inhibitory effect of the thiol containing compounds was comparable with 4-hexyl resorcinol and being significantly (P < 0.05) higher than ascorbic acid under all experimental conditions. The MRPs derived from cysteine/glucose model system were more active than their counterpart derived from cysteine/ribose model system. However, each of them could be considered as potential natural inhibitor having technological and commercial benefits to be applied in processed fruits.     

Effect of antibrowning agents on browning and intermediate formation in the glucose-glutamic acid model

In this study, the inhibitory effects of antibrowning agents on browning and the formation of intermediates such as 3-deoxyglucosone (3-DG) and hydroxymethylfurfural (HMF) were evaluated with a glucose-glutamic acid model for soybean paste. The initial antibrowning capacity was measured in the following order: pentasodium tripolyphosphate < citric acid and oxalic acid < cysteine and glutathione < sodium sulfite. Our data showed that antibrowning agents, such as pentasodium tripolyphosphate, citric acid, and oxalic acid, were maintained antibrowning capacities during storage at both 4 and 30 °C, respectively. However, both cysteine and glutathione was reduced with storage time, especially in the air. A marked effect of nitrogen treatment was noted for 3 of the antibrowning agents after storage in air at 30 °C in the following order: sodium sulfite < cysteine < glutathione. The formation ratio of 3-DG and HMF was higher after storage at 30 °C than at 4 °C. These compounds were produced most abundantly in the presence of sodium sulfite, and the yields were not related significantly to the degree of browning. Citric acid and oxalic acid were identified as the most effective in inhibitors of browning and intermediates, even during storage in air at 30 °C.     

Effect of ascorbic acid on the odours of cloudy apple juice

Ascorbic acid is used in apple juice as an antibrowning agent. This study investigated the effect of ascorbic acid (0.0–0.2% w/v) on the odours of cloudy apple juice using sensory evaluation and gas chromatography (GC). The increase in ascorbic acid concentration in the apple juice resulted in increases in green and unnatural odours and decreases in fresh, fruity and apple-like odours. In the GC determination, 23 volatile compounds were detected in apple juice. Aroma value, which showed the relative importance of volatile compounds, was used to elucidate the changes in odours of apple juice due to the addition of ascorbic acid. The aroma values of hexanal and trans-2-hexenal in the apple juice with 0.2% w/v ascorbic acid increased about 4 and 5-fold from those in the ascorbic acid-free apple juice, respectively. On the other hand, the aroma values of esters insignificantly changed in the apple juice with ascorbic acid. The increases in aroma values of aldehydes corresponded well with the increase in green odour in the apple juice with ascorbic acid.     

Effect of various anti-browning agents on phenolic compounds profile of fresh lettuce (L. sativa)

High performance liquid chromatography (HPLC) was used to characterise phenolic profile and to select the most effective anti-browning compound(s) on fresh lettuce. Four anti-browning agents, ascorbic acid, cysteine, citric acid and oxalic acid were tested for their effectiveness on preventing loss of phenolic compounds in lettuce during processing and storage. Aliquots of the reaction mixture were withdrawn at different times varying from 0 to 24 h, and directly analysed by HPLC. Protocatechuic acid, chlorogenic acid, ferulic acid, caffeic acid, p-coumaric acid and phloridzin were identified in fresh lettuce. Degradation of phenolic compounds followed a first-order kinetic pattern. The effect of anti-browning agents on first-order degradation rates of phenolic compounds was determined. Lettuce treated with oxalic acid and ascorbic acid maintained a higher level of phenolic compounds than citric acid and cysteine. Interestingly, cysteine had no positive effect for the prevention of oxidation of phenolic compounds even though it prevented browning in lettuce.     

VARIOUS ANTIBROWNING AGENTS AND GREEN TEA EXTRACT DURING PROCESSING AND STORAGE

The production of bottled green tea beverage has encountered a browning problem mainly caused by the autoxidation of flavanols (catechins). Five antibrowning agents, ascorbic acid, kojic acid, citric acid, L-cysteine, and glutathione, were tested for their effectiveness on preventing the color changes of green tea extract during processing and storage. One-tenth percent of the antibrowning agents were individually added to the freshly prepared green tea extracts, heat processed at 121C for 1 min, and then stored in a 50C oven for up to 12 days. Samples of fresh, processed, and stored tea extracts were measured for their color maintenance and (-)-epigallocatechin gallate (EGCG) content to compare the antibrowning and antioxidant effects of these agents, respectively. Results indicated that the antibrowning activity and antioxidant effect of individual agents often did not correlate with each other, but citric acid showed both significant antibrowning and antioxidant effects on green tea extract.     

Rhubarb Juice as a Natural Antibrowning Agent

To search for natural antibrowning agents, rhubarb juice was tested on fresh‐cut apple slices and found to have a potent effect. Liberty apple slices were treated in various concentrations of rhubarb juice (5%–100%), and the rate of discoloration at room temperature was measured by a Hunter Colorimeter. Apple slices treated in the 5%– 10% solution showed browning activity with dL values of 2.3 – 2.5 at two hours. However, the concentrations of rhubarb juice above 20% inhibited apple browning effectively with no change in the L value for several hours. Analysis of oxalic acid in rhubarb juice showed that the 20% solution contained about 67 mg/100g.     

Effect of Natural Antibrowning Agents on Color and Related Enzymes in Fresh-Cut Fuji Apples as an Alternative to the Use of Ascorbic Acid

ABSTRACT:  Polyphenoloxidase (PPO) and peroxidase (POD) were evaluated in fresh-cut Fuji apple slices and the effect of the individual or combined use of ascorbic acid, 4-hexylresorcinol, N-acetylcysteine, and glutathione on their respective activities was determined. Additionally, color changes during storage at 4 °C were measured throughout 14 d of storage. PPO activity increased with storage time and was inhibited by the individual use of N-acetylcysteine and glutathione. POD activity in the apple slices was effectively inhibited by the combined use of ascorbic acid with any of the other antibrowning agents. On the other hand, an individual treatment with 1% N-acetylcysteine helped in maintaining the color of fresh-cut apples during 14 d of storage, whereas the use of ascorbic acid was not enough to prevent color deterioration of the apple slices from the 1st day of storage. The results obtained corroborated the effectiveness of other natural antibrowning agents over the traditional use of ascorbic acid in the control of the enzymatic browning in the fresh-cut fruit industry.     

混浊苹果汁加工过程中的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.     

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。     

Effect of Dipping Pre-treatment with Unripe Grape Juice on Dried “Golden Delicious” Apple Slices

The consumption of apple chips is increasing in the last decades because of the consumer’s preferences towards healthy snacks. However, the enzymatic browning, which is attributed mainly to polyphenol oxidase (PPO, EC 1.10.3.1) activity, negatively affects the sensory, nutritional, and antioxidant properties of dried apples as a consequence of the oxidation of phenolic substrates during post-harvest stages. The antibrowning and antioxidant effects of dipping pre-treatments with unripe grape juice as well as reference formulations including a mixture of 1% w/v ascorbic acid and 1% w/v citric acid, 6% w/v NatureSeal®, and 0.1% w/v sodium metabisulfite were evaluated by spectrophotometric and colorimetric assays on dried “Golden Delicious” apple slices. Based on HPLC analysis, the treated apple slices were enriched with bioactive compounds which effectively improved antioxidant capacity and limited enzymatic browning by increasing lightness, reducing color change, and inhibiting PPO activity. Hence, the juice of unripe grapes recovered as agricultural wastes during bunch thinning of vineyards could be proposed as a safe, inexpensive, and eco-friendly alternative to conventional antibrowning treatments in apple processing.     

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     

Effect of various inhibitors on enzymatic browning,antioxidant activity and total phenol content of fresh lettuce (Lactuca sativa)

In this study, polyphenol oxidase (PPO) was isolated from fresh lettuce. Its optimum temperature and pH were found to be 40 °C and 7.0, respectively. Lettuce PPO was shown to use catechin, catechol, chlorogenic acid, caffeic acid and gallic acid as substrates. Among the substrates used, the greatest substrate specificity was observed with chlorogenic acid. Lettuce PPO was sensitive to some inhibitors. Ascorbic acid, cysteine, oxalic acid and citric acid were tested as potential inhibitors of lettuce PPO. Cysteine was the most effective inhibitor. Total phenol and total antioxidant activity contents were also determined in the presence of these inhibitors at room and refrigerator temperatures. Ascorbic acid and cysteine increased the total antioxidant activity of lettuce while citric and oxalic acids had no effect on the total antioxidant activity. Lettuce phenolics were protected from oxidation by ascorbic acid and cysteine.     

A Potent Antibrowning Agent from Pine Needles of Cedrus deodara: 2R,3R‐Dihydromyricetin

This article focuses on finding the novel antibrowning agents from the pine needles of Cedrus deodara and studying its antibrowning effect. By bioassay guide of tyrosinase inhibitory activity, the main active compound was isolated and purified from 50% methanol extract of pine needles of C. deodara through macroporous resin Diaion HP‐20 column chromatography and high‐performance liquid chromatography. Based on mass and nuclear magnetic resonance data, the active compound was identified as 2R,3R‐dihydromyricetin, which showed the potent monophenolase and diphenolase inhibitory activities. Moreover, 2R,3R‐dihydromyricetin exhibited a strong ABTS radical scavenging activity with a dose‐dependent manner. The antibrowning efficacy of 2R,3R‐dihydromyricetin was evaluated by monitoring the changes of L*, a*, and b* values and total color difference (△E) on fresh‐cut apple slices. It was found that 2R,3R‐dihydromyricetin was effective in inhibiting the browning of apple slices treated with a concentration as low as 0.05% at 25 °C for 24 h. Its antibrowning effect was significantly better than ascorbic acid (0.5%) alone. Furthermore, 2R,3R‐dihydromyricetin showed a good synergistic antibrowning effect with ascorbic acid. This is the first report that 2R,3R‐dihydromyricetin from pine needles of C. deodara may be used as a potential antibrowning agent in protecting against food browning.     

Antibrowning and antimicrobial activities of the water-soluble extract from pine needles of Cedrus deodara

The antibrowning and antimicrobial activities of the water-soluble extract from pine needles of Cedrus deodara (CDE), a traditional Chinese medicine and raw materials of pine needle tea, was investigated. Total phenols of CDE were 31.4 ± 0.53 mg gallic acid equivalent/g, and total flavonoids were 23.1 ± 0.79 mg rutin equivalent/g. CDE showed a strong antioxidant activity against ABTS free radicals with IC(50) (the half-inhibitory concentration) of 25.5 ± 0.64 μg/mL. In mushroom tyrosinase inhibitory assay, IC(50) values were 2.1 ± 0.98 and 2.27 ± 0.93 mg/mL for monophenolase and diphenolase, respectively. Evaluated by detecting changes of L* (indicated the darkness of sample), a* (indicated the redness of sample), and b* (indicated the yellowness of sample) values in fresh-cut apple slices model, CDE showed a significant antibrowning effect when compared with ascorbic acid. In addition, it was discovered that CDE in combination with 0.5% ascorbic acid exhibited a synergistic antibrowning effect. Meanwhile, CDE was observed to show a potent antimicrobial effect on all of the tested Gram-positive and Gram-negative bacteria. In conclusion, the results of the present research suggested that pine needles of C. deodara could be used as a natural resource of antibrowning and antimicrobial agents in food preservation. PRACTICAL APPLICATION: The present study provides a theoretical basis for the potential application of pine needles of C. deodara to be used as a natural resource of antibrowning and antimicrobial agents in food industry.     

Antioxidative properties and phytochemical composition of Ballota nigra infusion

The ability of Ballota nigra (Lamiaceae) infusion to act as a scavenger of DPPH radical, reactive oxygen species (superoxide radical, hydroxyl radical, hypochlorous acid) and nitric oxide was investigated. The tested infusion mainly exhibited a potent scavenging effect on DPPH, nitric oxide and superoxide radicals. In hydroxyl radical assay a potent pro-oxidant activity was noticed. No effect was found against hypochlorous acid. A phytochemical study was also undertaken, and seven phenolic compounds (chlorogenic, caffeic and caffeoylmalic acids, ballotetroside, forsythoside B, verbascoside and allysonoside) and eight organic acids (oxalic, aconitic, citric, ascorbic, malic, quinic, shikimic and fumaric acids) were identified and quantified by HPLC/DAD and HPLC/UV, respectively. Forsythoside B and quinic acid were revealed to be the main compounds in this infusion.     

Antibrowning and Antimicrobial Properties of Sodium Acid Sulfate in Apple Slices

ABSTRACT: There are few available compounds that can both control browning and enhance microbial safety of fresh‐cut fruits. In the present study, the antibrowning ability of sodium acid sulfate (SAS) on “Granny Smith” apple slices was first investigated in terms of optimum concentration and treatment time. In a separate experiment, the apple slices were treated with water or 3% of SAS, calcium ascorbate, citric acid, or acidified calcium sulfate for 5 min. Total plate count, color, firmness, and tissue damage were assessed during a 21‐d storage at 4 °C. Results showed that the efficacy of SAS in inhibiting browning of apple slices increased with increasing concentration. A minimum 3% of SAS was needed to achieve 14 d of shelf life. Firmness was not significantly affected by SAS at 3% or lower concentrations. Antibrowning potential of SAS was similar for all treatment times ranging from 2 to 10 min. However, SAS caused some skin discoloration of apple slices. When cut surface of apple slices were stained with a fluorescein diacetate solution, tissue damage could be observed under a microscope even though visual damage was not evident. Among the antibrowning agents tested, SAS was the most effective in inhibiting browning and microbial growth for the first 14 d. Total plate count of samples treated with 3% SAS was significantly lower than those treated with calcium ascorbate, a commonly used antibrowning agent. Our results suggested that it is possible to use SAS to control browning while inhibiting the growth of microorganisms on the apple slices if the skin damage can be minimized. Practical Application: Fresh‐cut apples have emerged as one of the popular products in restaurants, schools, and food service establishments as more consumers demand fresh, convenient, and nutritious foods. Processing of fresh‐cut apples induces mechanical damage to the fruit and exposes apple tissue to air, resulting in the development of undesirable tissue browning. The fresh‐cut industry currently uses antibrowning agents to prevent discoloration. However, the antibrowning solutions can become contaminated with human pathogens such as Listeria monocytogenes, and washing of apple slices with the contaminated solutions can result in the transfer of pathogens to the product. It would be ideal if an antibrowning compound prevented the proliferation of human pathogens in solutions and minimized the growth of pathogens during storage. The study was conducted to investigate antibrowning and antimicrobial properties of sodium acid sulfate (SAS) in comparison with other common antibrowning agents on Granny Smith apples. Results showed that among the antimicrobial agents we tested, SAS was the most effective in inhibiting browning and microbial growth for 14 d at 4 °C. However, SAS caused some skin discoloration of apple slices. Overall, SAS can potentially be used to inhibit tissue browning while reducing the microbial growth on apple slices. The information is useful for the fresh‐cut produce industry to enhance microbial safety of fresh‐cut apples while minimizing browning, thus increasing the consumption of the health benefiting fresh fruit.     

可食性复合涂膜保鲜剂对延长鲜切苹果货架期的研究

本文主要研究了可食性涂膜剂与抗褐变剂复配后对鲜切苹果的保鲜效果。研究表明:25℃条件下,苹果切块经卡拉胶(0.5%)涂膜剂和乳清浓缩蛋白WPC(5%)涂膜剂处理后,其呼吸强度可分别降低5%和20%。在可食性涂膜剂中添加不同的抗褐变剂对苹果切块有良好的护色效果,添加1%CaCl2可增加产品的硬度,同时这些复合保鲜剂可提高苹果切块的感官指标和抑制微生物繁殖,而5%WPC涂膜液+1%CaCl2+1%抗坏血酸复合液浸泡苹果切块,3℃条件下贮藏2w后保鲜效果最佳。