Inhibition Of Browning Research Articles

Metabolomic insights into the browning inhibition of fresh-cut apple by hydrogen sulfide

Hydrogen sulfide (H2S) is known to effectively inhibit the browning of fresh-cut apples, but the mechanism at a metabolic level remains unclear. Herein, non-targeted metabolomics was used to analyze metabolic changes in surface and internal tissues of fresh-cut apple after H2S treatment. The results showed that prenol lipids were the most up-accumulated differential metabolites in both surface and inner tissue of fresh-cut apple during browning process, which significantly down-accumulated by H2S treatment. H2S treatment reduced the consumption of amino acid in surface tissue. Regarding inner tissue, H2S activated defense response through accumulation of lysophospholipid signaling and induced the biosynthesis of phenolic compounds. We therefore propose that H2S inhibited the surface browning of fresh-cut apple by reducing the accumulation of prenol lipids, directly delaying amino acid consumption in surface tissue and indirectly regulating defense response in inner tissue, which provides fundamental insights into browning inhibition mechanisms by H2S.

Inhibitory effect of thiol compounds on browning precursors and intermediates in sorbitol/glycine system.

Sorbitol as a sweetener is often thought to be unable to participate in the Maillard reaction causing browning. However, browning of a system was found to be significant when sorbitol was mixed with glycine and heated. The thiol compounds glutathione and cysteine were added to the system, and the inhibition mechanism of the two on the browning of the system was studied by combining the changes of precursor substances, intermediate products and browning degree. When the concentration of thiol compounds reached 25 mg mL-1, both could make the browning inhibition of the system more than 80%, and the accumulated glucose concentration was reduced to <35% of the control. The production of 3-deoxyglucosone, a precursor of melanoidin, was significantly reduced. Glutathione and cysteine directly inhibited the production of substrates in the sorbitol/glycine system, reduced glucose accumulation through competitive consumption and captured highly active intermediates through sulfhydryl groups. This has implications for the browning control of food systems containing sugar alcohols. © 2024 Society of Chemical Industry.

Sericin and Pineapple Fruit Extract as Natural Agents Inhibiting Browning and Improving Antioxidant Activity in Fresh-cut Ripe Mangoes cv. Nam Dok Mai

Recently, the use of natural agents to improve quality has attracted a lot of attention on fresh-cut produce and minimally processed fruit. The aims of this work were to investigate the efficiency of sericin and fresh pineapple juice (selected natural agents) on browning inhibition and antioxidant activity of fresh-cut ‘Nam Dok Mai’ mangoes during refrigeration (4°C). Based on a preliminary study and our previous work, 2% sericin (S) and 50% pineapple juice (PJ) were selected. Biological parameters related to enzymatic browning incidence, antioxidants and antioxidant enzyme activity of the fresh-cut mangoes immersed in 2% S, 50% PJ and 50% PJ incorporated with 2% S (PJ+S) were investigated. Immersion in S, PJ or PJ+S inhibited enzymatic browning due to delaying of discoloration, lowering of browning index (BI) and increases in polyphenol oxidase (PPO) and peroxidase (POD) activities compared to control treatment. The lowest PPO and POD activities and total phenolic content were found in the S treated fresh-cut mangoes. PJ+S treated fresh-cut mangoes had antioxidant activities higher than other treatment. All treatments enhanced the activities of antioxidant enzymes, especially PJ immersion. Therefore, S and PJ show potential as natural agents that can inhibit browning and improve antioxidant activity in fresh-cut mangoes during refrigeration.

Effect of phytic acid on the appearance of yellow alkaline noodles: Color and dark spots

Phytic acid (PA) could increase the yellowness value of yellow alkaline noodles (YAN), as well as significantly reduce the generation of dark spots on the surface of YAN by suppressing polyphenol oxidase (PPO) browning. In this paper, the inhibition mechanism of PA on PPO browning was mainly studied. In the produced YAN sheets, the PPO activity and free quinone content showed a gradual decrease with increasing PA addition, while the free phenol content gradually increased. This indicated that PA could inhibit PPO browning and was an effective browning inhibitor. In the constructed in vitro PPO solution, the anti-PPO browning mechanism of PA was mainly through chelating Cu2+ in the active center. The DPPH radical scavenging rate of PA was measured, and it was found that PA could inhibit PPO browning, which was related to the antioxidant capacity. The effect of PA on browning products was analyzed using HPLC, and the results of the study showed that PA could reduce the peak area of the browning products, thus reducing the generation of dark spots.

Effect of herbal application on browning inhibition and physico-chemical quality of pear (Pyrus communis) slices

The main objective of the research study is to evaluate the effect of herbs (O. basilicum, O. vulgare, C. sinensis) extract-coated pear slices on its physiochemical quality attributes, discoloration rate, and browning enzyme activity in comparison with chemical (ascorbic acid) coated pear slices over 15 days at 4 ± 1 ℃. A significant difference (p < 0.05) between herbs and ascorbic acid-coated pear slices was obtained in terms of physiochemical quality attributes, whereby the highest variation was obtained in uncoated pear slices (control) and the least variation was observed in herbs-coated pear slices, more specifically C. sinensis spray, and dip (6 min) extract showed the highest inhibition of PPO/POD activity and the minimum browning index was noticeable throughout 15 days of storage. These findings showed that herbal extract coating application to fresh-cut pears might be a desirable strategy to alleviate discoloration, also considered to be an effective alternative to chemical coating.

Antioxidant and antibrowning properties of Maillard reaction products in food and biological systems.

Oxidative damage refers to the harm caused to biological systems by reactive oxygen species such as free radicals. This damage can contribute to a range of diseases and aging processes in organisms. Moreover, oxidative deterioration of lipids is a serious problem because it reduces the shelf life of food products, degrades their nutritional value, and produces reaction products that could be toxic. Antioxidants are effective compounds for preventing lipid oxidation, and synthetic antioxidants are frequently added to foods due to their high effectiveness and low cost. However, the safety of these antioxidants is a subject that is being discussed in the public more and more. Synthetic antioxidants have been found to have potential negative effects on health due to their ability to accumulate in tissues and disrupt natural antioxidant systems. During thermal processing and storage, foods containing reducing sugars and amino compounds frequently produce Maillard reaction products (MRPs). Through the chelation of metal ions, scavenging of reactive oxygen species, destruction of hydrogen peroxide, and suppression of radical chain reaction, MRPs exhibit excellent antioxidant properties in a variety of food products and biological systems. Also, the capacity of MRPs to chelate metals makes them as a potential inhibitor of the enzymatic browning in fruits and vegetables. In this book chapter, the methods used for the evaluation of antioxidant activity of MRPs are provided. Moreover, the antioxidant and antibrowning activities of MRPs in food and biological systems is discussed. MRPs can generally be isolated and used as commercial preparations of natural antioxidants.

Effect of Ascorbic Acid, Activated Charcoal and Dark Incubation on Browning Intensity of Saurauia bracteosa In Vitro Culture

Saurauia bracteosa, also known as Pirdot, is an endemic woody plant of the Actinidiaceae family with medicinal properties. Its population decline in nature has led to a vulnerable status, prompting conservation efforts, such as in vitro culture. Browning poses a significant challenge in the woody plant in vitro culture. Browning inhibitors such as ascorbic acid, activated charcoal and dark incubation can be used to address this issue. This study aims to determine the effect of ascorbic acid, activated charcoal and incubation conditions on browning inhibition of S.bracteosa. The study employed a Completely Randomized Design with 12 treatments on leaf explants, repeated five times. Observations, including the time of browning formation, percentage of browning, intensity of browning and percentage of live explant were carried out for 30 days and analyzed using ANOVA followed by DMRT. The results showed that the addition of activated charcoal in MS media with dark incubation delayed the browning formation time (12.40 DAI) while the adding ascorbic acid in MS media and dark incubation resulted in the lowest browning intensity (0.22). These research findings can serve as a foundational protocol for browning prevention, supporting the successful in vitro conservation of S. bracteosa.

Bamboo leaf extract treatment alleviates the surface browning of fresh-cut apple by regulating membrane lipid metabolism and antioxidant properties.

The effect of bamboo leaf extract (BLE) on controlling the browning of fresh-cut apple stored at 4 °C was investigated. Browning index, H2 O2 content, O2 - production rate, malondialdehyde (MDA) contents, total phenolic content (TPC) and soluble quinone content (SQC), the activities of polyphenol oxidase (PPO), peroxidase (POD), lipoxygenase (LOX), superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), DPPH (2,2-diphenyl-2-picryl-hydrazyl) and ABTS [2,2-azinobis(3-ethylbenzothiazoline- 6-sulfonic acid)] radical scavenging activities, and the expression of genes related to browning were all investigated. BLE effectively alleviated the surface browning of fresh-cut apple, accompanied by a reduction in SQC, LOX activity, H2 O2 , O2 - production rate and MDA accumulation. Furthermore, BLE treatment enhanced the TPC, enzymatic (SOD, CAT, APX and POD) and non-enzymatic antioxidant activities. Principal component analysis and Pearson correlation analysis found the browning inhibition by BLE is not through the reduction of phenolic substrates and PPO activity. BLE controls the browning of fresh-cut apple by increasing the antioxidant capacity to scavenge ROS, which could alleviate oxidative damage and maintain the membrane integrity. © 2023 Society of Chemical Industry.

Influence of plasma-activated γ-aminobutyric acid on tissue browning and water migration in fresh-cut potato during storage

Plasma-activated water (PAW) accelerated tissue browning in fresh-cut fruit. In this study, plasma-activated γ-aminobutyric acid (PG) was applied in potato slices. We aimed to contrast the impacts of PAW, γ-aminobutyric acid (GABA), and PG on changes in phenol metabolism and water distribution in potato slices. The results highlighted that PG proved to be the most effective treatment in terms of sterilization, inhibition of browning, and prevention of water. PG facilitated the activation of antioxidant enzymes, thereby eliminating reactive oxygen species and maintaining the integrity of cell membranes. Furthermore, PG exhibited the capacity to inhibit enzymatic browning caused by polyphenols, which was achieved through enhancing the activities of enzymes associated with phenylpropane metabolism and suppressing polyphenol oxidase activity. PG also protected the surface integrity of the potato slices as evident from SEM analysis. Additionally, NMR result indicated that PG played a role in maintaining free water content and inhibiting moisture migration.

Effects of ascorbic acid and kelulut honey as antibrowning agent on the quality of minimally processed jackfruit (Artocarpus heterophyllus)

Minimally processed jackfruit is gaining popularity for its economic importance to the fruit industry, but its high susceptibility to enzymatic browning has been its limitation. This study determines the effects of applying ascorbic acid (AA) and kelulut honey (KH) on the shelf life of minimally processed jackfruit (MPJ) stored at chill and ambient temperature for 12 days. The quality of treated and untreated minimally processed jackfruit was evaluated by weight loss, firmness, colour (L* and b*), ascorbic acid content and browning inhibition. A microbiological analysis was performed to estimate the shelf-life. The MPJs dipped in 3% ascorbic acid and 3% kelulut honey and stored at 4°C showed the least weight loss of 0.75% and 0.42%, respectively, and the significantly least reduction in firmness of 67.93% and 65.24%, respectively. Ascorbic acid was found to be more efficient in reducing the discolouration of MPJ compared to kelulut honey. Depending on the temperature, the 3% KH dipping solution is more efficient than ascorbic acid in inhibiting the browning activity of MPJ with an inhibition of 9.29%, retaining ascorbic acid content (16.45 mg/100 g) and inhibiting microbial growth (6.20 log CFU/g) of MPJ up to 9 days of storage.

Inhibitory mechanism of esculetin on tyrosinase and browning of fresh-cut apple: New perspectives

The anti-tyrosinase mechanism of esculetin has been systematically investigated by various spectroscopic techniques and molecular simulation. And the outcomes confirmed that esculetin was a competitive and excellent tyrosinase inhibitor (IC50=43 ± 0.5 µmol L−1). The binding of esculetin to tyrosinase affected the hydrophobic microenvironment of the enzyme and altered its conformation. Thermodynamic analysis and molecular docking demonstrated that the binding was driven by hydrophobic interaction and hydrogen bonding. Circular dichroism and molecular dynamic analysis revealed that esculetin induced the structural stretching of tyrosinase and slightly impacted the microenvironment of amino acid residues. Cell assays further demonstrated that esculetin inhibited intracellular tyrosinase activity and melanin production but showed no significant effect on cell proliferation. Additionally, studies on browning inhibition indicated that esculetin delayed the browning of fresh-cut apples by suppressing phenolic metabolism, strengthening antioxidant systems, and reducing membrane-lipid peroxidation. The above discoveries offered new viewpoints for understanding the suppressive mechanism of esculetin on tyrosinase and browning, as well as scientific evidence for its potential application in food preservation and medicine.

Condensed tannins from the leave of Dimocarpus longan Lour. exhibit anti-tyrosinase, anti-melanogenesis, anti-browning, anti-α-glucosidase, and anti-glycation activities

Dimocarpus longan Lour. is a valuable industrial crop for its broad applications in food, traditional Chinese medicine, and other fields. In this paper, condensed tannins were isolated from the leave of D. longan Lour., and their structure, anti-tyrosinase, anti-melanogenesis, anti-browning, anti-α-glucosidase, and anti-glycation properties were methodically clarified. The joint application of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), electrospray ionization time-of-flight mass spectrometer (ESI+ TOF MS), and high-performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) confirmed that the longan leave condensed tannins (LLCTs) were polymers of procyanidins (majority) and prodelphinidins. The polymers powerfully inhibit tyrosinase (TY) with a competitive mechanism. These compounds altered the microenvironment of the binding site through hydrophobic interaction and hydrogen bond, and caused conformational modification of the enzyme by changing the polypeptide framework and secondary structure, leading to a decrease in TY activity. Cell assays further suggested that LLCTs exhibited a strong inhibition against intracellular TY activity and melanin production, and caused apoptosis in B16F10 cells. Anti-browning studies demonstrated that LLCTs suppress the browning of fresh-cut apples. Furthermore, the LLCTs exhibited an impressive inhibition on both α-glucosidase and nonenzymatic glycation. Therefore, this study confirms the potential of LLCTs as new inhibitors of tyrosinase, melanogenesis, browning, α-glucosidase, and nonenzymatic glycation, which provided a theoretical basis for the potential utilization of these polymers in the cosmetics, pharmaceutical, and food industries.

Synthesis, Antioxidant, and Antifungal Activities of β-Ionone Thiazolylhydrazone Derivatives and Their Application in Anti-Browning of Freshly Cut Potato.

In order to develop a new type of antioxidants with high efficiency, a series of β-ionone thiazolylhydrazone derivatives were designed and synthesized from β-ionone, and their structures were characterized by 1H-NMR, 13C-NMR, FT-IR, and HR-MS. The antioxidant test in vitro indicated that most of the target compounds had high biological activity. Among them, compound 1k exhibited very strong DPPH (1,1-diphenyl-2-picrylhydrazyl radical)-scavenging activity with a half-maximal effective concentration (IC50) of 86.525 μM. Furthermore, in the ABTS (2,2-azinobis (3-ethylbenzothiazoline-6-sulfonate) diammonium salt)-scavenging experiment, compound 1m exhibited excellent activity with an IC50 of 65.408 μM. Their biological activities were significantly better than those of the positive control Trolox. These two compounds, which have good free-radical-scavenging activity in vitro, were used as representative compounds in the anti-browning experiment of fresh-cut potatoes. The results showed that 1k and 1m had the same anti-browning ability as kojic acid, and they were effective browning inhibitors. In addition, it is well known that microbial infection is one of the reasons for food oxidation. Therefore, we investigated the antifungal activity of 25 target compounds against eight plant fungi at a concentration of 125 mg/L. The results indicated that these compounds all have some antifungal activity and may become new potential fungicides. Notably, compound 1u showed the best inhibitory effect against Poria vaporaria, with an inhibition rate as high as 77.71%; it is expected to become the dominant structure for the development of new antifungal agents.

Distinct response of adipocyte progenitors to glucocorticoids determines visceral obesity via the TEAD1-miR-27b-PRDM16 axis.

Visceral obesity contributes to obesity-related complications; however, the intrinsic mechanism of depot-specific adipose tissue behavior remains unclear. Despite the pro-adipogenesis role of glucocorticoids (GCs) in adipogenesis, the role of GCs in visceral adiposity rather than in subcutaneous adipose tissue is not established. Because adipocyte progenitors display a striking depot-specific pattern, the regulatory pathways of novel progenitor subtypes within different depots remain unclear. This study describes a cell-specific mechanism underlying visceral adiposity. A diverse panel of novel depot-specific adipose progenitors was screened in mice and human samples. The transcriptome distinction and various responses of novel progenitor subtypes of GCs were further measured using the GC receptor-chromatin immunoprecipitation assay and RNA sequencing. The mechanism of novel subtypes was identified using transposase-accessible chromatin analysis and bisulfite sequencing and further confirmed using precise editing of CpG methylation. Platelet-derived growth factor receptor α (PDGFRα+ ) progenitors, which were dominant in the visceral adipose tissue, were GC-sensitive beige adipose progenitors, whereas CD137+ progenitors, which were dominant in the subcutaneous adipose tissue, were GC-passive beige adipose progenitors. Expression of miR-27b, an inhibitor of adipocyte browning, was significantly increased in PDGFRα+ progenitors treated with GCs. Using transposase-accessible chromatin analysis, bisulfite sequencing, and precise editing of CpGmethylation, TEA domain transcription factor 1 (TEAD1) was discovered to be uniquely hypomethylated in PDGFRα+ progenitors. GCs inhibited the PDGFRα+ progenitors' browning process via miR-27b, which was transcriptionally activated by the collaboration of TEAD1 with the GC receptor. These data provide insights into the mechanism of depot-specific variations in high-fat diet-induced obesity.

Abstract P3001: Regulation Of Perivascular Adipose Tissue By Follistatin In Hypertension

Follistatin lowers BP and improves resistance artery health in spontaneously hypertensive rats (SHR), a model of essential HTN. Functionally, follistatin improves smooth muscle contraction and endothelium-dependent relaxation. Structurally, increased medial collagen was inhibited. Vascular ROS were also reduced. Perivascular adipose tissue (PVAT) regulates vascular tone via release of vasoactive substances. Oxidative stress in PVAT, as in HTN, induces release of contractile agents. Transition from white to brown PVAT is associated with decreased risk of CVD. We analyze effects of follistatin on PVAT and its regulation of vessel function in SHR and normotensive Wistar Kyoto (WKY) rats. White and brown PVAT were dissected from treated rats; arteries were isolated from untreated donors. PVAT was introduced near strain-matched donor arteries and assessed for ROS levels and contractility using DHE and wire myography, respectively. In some vessels, endothelium was denuded to assess its contribution to contraction. Follistatin reduced ROS, hypercontractility, and improved relaxation in a PVAT-dependent manner. Brown PVAT induced significant anti-contractile and antioxidant effects. Elevated expression of adipose tissue browning markers and decreased adipocyte area with follistatin, support PVAT browning effects. Endothelium removal results in augmented vessel constriction, effects reduced by follistatin. Follistatin improves SHR smooth muscle tone in a PVAT-dependent manner, likely through the inhibition of vascular ROS and browning of PVAT. Future work will profile PVAT effects of follistatin through unbiased proteomic analysis. Although most vessels are surrounded by PVAT, studies of PVAT-vessel interaction in HTN are few. By characterizing PVAT dysfunction, we aim to outline specific PVAT-mediated pathways involved in lowering BP and improving vascular function and structure. Results will provide new insights into PVAT-targeted therapy for essential HTN, allowing potential translation of benefits to obesity and other diseases exhibiting PVAT dysfunction.

Effect of phytol isolated from edible red alga (Bangia fusco-purpurea) on tyrosinase inhibition and its application on food preservation

Enzymatic browning is one of the major problems in food industry, especially for damaged fruits and vegetables during post-harvest handling and processing. An efficient approach to reduce enzymatic browning is to inhibit key polyphenol oxidases causing browning reactions, for example tyrosinase. Tyrosinase inhibitors from natural sources are more attractive considering the importance of food safety and application. B. fusco-purpurea is a edible alga with potential inhibiting tyrosinase. Therefore, we purified and characterized new tyrosinase inhibitors from the seaweed. Phytol, identified in the crude extract of B. fusco-purpurea inhibited tyrosinase with half maximal inhibitory concentration (IC50) of 32.4 ± 3.06 μg/mL as a reversible and competitive inhibitor. Phytol acted as tyrosinase inhibitor, antioxidant, and reducing agent in inhibition of enzymatic browning mechanisms. Then, with the increase concentration of phytol added in homogenates squeezed from apple, pear, and potato, higher browning inhibition was observed with browning index increased. Our findings suggest that phytol isolated from edible red alga could be a potential anti-browning agent.

Inhibition of postharvest rachis browning of table grapes by sulfur dioxide: Evidence from phenolic metabolism and sulfur assimilation

Rachis browning is a visual marker of table grape freshness and plays a vital role in consumer preference and food waste. In this study, the role of sulfur dioxide (SO2) in maintenance of quality attributes of grape rachis during shelf-life was systematically studied, and results demonstrated that the rachis browning was significantly inhibited, and endogenous phenolic metabolism and sulfur assimilation were affected by exogenous SO2, at both transcriptional and metabolic levels. Furthermore, SO2 treatment promoted the accumulation of major phenolic compounds, such as (+)-catechin, (-)-epicatechin, (-)-epicatechin gallate, and proanthocyanidins, by increasing the transcript levels of VvLAR and Vv3GT genes involved in flavonoid pathway. Besides, gene expression involved in sulfite assimilation was also activated by exogenous SO2, resulting in the accumulation of sulfur-containing metabolites, including cysteine, hydrogen sulfide, and glutathione. The present study provided the first evidence for the anti-browning effect of SO2 through the accumulation of flavanols and sulfur-containing compounds.

Quality characteristics of fresh cut apples during storage according to processing steps and browning inhibitor treatment

We examined the changes in the physicochemical quality characteristics and antioxidant activity of fresh-cut Fuji apples (Malus pumila) during processing and storage after treatment with browning inhibitors. The primary aim was to elucidate processing suitability and storability. We observed that in the processing stage of slicing fresh Fuji apples, there were no significant differences in 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging ability and ferric-reducing antioxidant power (FRAP). However, after NaClO treatment, total flavonoid and total polyphenol contents decreased. When freshcut Fuji apples were treated with browning inhibitors and stored at 4°C, the L value and hardness decreased; however, the weight loss rate increased based on the storage period of all fruit groups treated with Citrus unshiu Markovich (CuM), calcium ascorbate (CA), and ascorbic acid (AA). The pH increased after 2 days of storage in 1% CuM and after 6 days of storage in 1% CA; however, no changes in pH were observed during the storage period in 1% AA. The DPPH radical scavenging activity was generally good under storage conditions of 1% AA at 4°C and 1% CA at 20°C. Furthermore, FRAP remained relatively constant under storage conditions of 1% CA. The quality characteristics and antioxidant activity of fresh-cut fruits during processing and storage can be used as basic data for industries. Furthermore, we can gain confidence in quality improvements by improving the production and distribution environment of fresh-cut agricultural products.

Inhibitory effects of peppermint extracts on the browning of cold-stored fresh-cut taro and the phenolic compounds in extracts

Fresh-cut taros are prone to browning even though they are stored at low temperatures, which leads to the quality deterioration and markedly limits the shelf life. The browning control of fresh-cut food with natural substances has received much attention. This study evaluated anti-browning potential of peppermint extracts in fresh-cut taro during cold storage. The results showed that both peppermint leaf and shoot extract (LE and SE) treatments could effectively retard the browning of fresh-cut taros. Furthermore, LE and SE treatments reduced the activities of phenylalanine ammonialyase and lipoxygenase, the contents of total phenolic compound (TPC), total flavonoids, soluble quinones, malondialdehyde and hydrogen peroxide, enhanced peroxidase activity and antioxidant capacity in taro slices. The TPC contents were reduced by 4.05 and 17.71%, and the T-AOC was enhanced by 28.73 and 28.82% as compared to the control at 12 d. These results together suggested that peppermint extract treatments reduced phenolic biosynthesis but enhanced antioxidant activity. However, LE and SE treatments did not inhibit polyphenol oxidase (PPO) activity, suggesting that peppermint extract treatments reduced taro browning was not through inhibition of phenolic oxidation. More than 240 phenolic-related compounds including caffeic acid, ferulic acid and p-Coumaric acid were identified in peppermint extracts through UPLC–MS/MS analysis, suggesting that phenolics may be bioactive substances reducing taro browning. In conclusion, this study demonstrates that peppermint extract is a promising natural anti-browning ingredient and phenolic compounds may function on taro browning inhibition.

Accurate pH decrease induced inactivation of myrosinase and polyphenol oxidase in salted radish for color improvement

Yellowing even browning of radish commonly occurred during the traditional pickling. This research aimed to determine the reason of yellowing of pickled radish, and propose the method for yellowing inhibition. The activity of endogenous enzymes in radish were analyzed, and the relationship between the activity and the browning was investigated. Myrosinase and polyphenol oxidase (PPO) were found as main potential enzymes resulting in browning of radish. During traditional salting processing, the myrosinase activity decreased, particularly at a high speed in the first 14 days, while the PPO activity did not decrease observably. The a* and b* values of salted radish were significantly correlated with myrosinase and PPO activity. Acid treatment was observed to be effective for browning inhibition of radish during soaking and storage, and the low pH conditions contributed to the preservation of original green color of radish. Stronger acidification during the first 3 d played a much more important role in browning inhibition than following weaker acidification treatment for 27 d. Low pH showed an inhibition effect on PPO activity, but myrosinase reactivity was more sensitive to pH changes than PPO. The myrosinase in the radish treated in the pickling solution at pH 2 was completely inactivated during the first 3 days. Further investigation of pH effect on improvement of salted radish color concluded that pH 2.4 was the optimal pH for the inactivation of myrosinase and PPO. Accordingly, short-term accurate acidification coupled with traditional salting treatment was originally proposed for effective browning inhibition of pickled radish.