Enzymatic Browning Reactions Research Articles

Development of Ready to Cook Banana Pseudo Stem Vermicelli Upma Mix with Quality Evaluation

The present research aimed to evaluate the effect of incorporation of commonly discarded part banana pseudo stem (BPS) for the development of ready-to-cook (RTC) vermicelli upma mix. BPS was subjected to preliminary treatment with citric acid solution (0.5%) to prevent an enzymatic browning reaction during the preparation of flour. Vermicelli was prepared by partial substitution of whole wheat flour and semolina with BPS flour at the level of 5, 10, 15, 20 and 25% (T1, T2, T3 & T4). Effect of incorporation of BPS flour on- the physical, functional and organoleptic properties were studied. Among all the variations tested T3 (20%) was accepted with optimal cooking characteristic hence, taken for preparation of vermicelli BPS upma mix and compared with control. The BPS vermicelli upma mix has got significantly more ash (27.2 g), soluble fiber (2.64 g) and insoluble fiber (15.76 g) and also rich in minerals such as potassium (1203.6 mg %) and calcium (5.72 mg %). It also contained higher antioxidant activity (3.93 mg %), total phenols (583.44 mg GAE %), saponins (291.06 mg %), tannins (4.01 mg %) and flavonoid (165.7 mg %). However, vermicelli upma mix was packed in MMP and LDPE pouches and stored at ambient conditions (25±50C) for a period of six months.

Chlorine Dioxide Delays Enzymatic Browning in Postharvest Cherimoya and Enables Establishment of Kinetics Substrate Model

Cherimoya (Annona squamosa L.) is a nutrient-rich fruit. However, it is not easy to store because of its susceptibility to browning. In order to prolong the storage period of cherimoya, the fruit was treated with chlorine dioxide (ClO2) at different concentrations (20, 40, 60, 80, and 100 mg L−1) and stored at 15 °C for 8 days. The quality and biochemical indexes of the fruit were investigated using a chromameter, high-performance liquid chromatography and scanning electron microscopy, etc. The results showed that all the treatments with various concentrations of ClO2 could delay the increase in the browning index, loss of weight, and decrease in hardness. Meanwhile, ClO2 treatment effectively reduced the consumption of starch, titratable acids, and phenolics as well as inhibited the polyphenol oxidase (PPO) activity and enzymatic oxidation. It can be seen from the Fourier transform infrared spectrum (FTIR) that the C=O stretching peak at 1731 cm−1 disappeared at a ClO2 concentration of 60 mg L−1. We think the ClO2 treatment may inhibit the oxidation of phenol to quinone. According to the Arrhenius formula, the values of the apparent activation energy (Ea) for enzymatic browning reaction were estimated. The Ea with catechol in cherimoya pericarp and flesh were 67.00 and 47.83 kJ mol−1, respectively. It was found that the phenolic enzyme reaction with catechol has a much smaller Ea and a higher affinity for PPO. Therefore, treatment with ClO2 at a suitable concentration for cherimoya stored at 15 °C could effectively maintain fruit quality and prolong the storage period; the most appropriate concentration is 60 mg L−1.

Protecting celtuce (Lactuca sativa L. var. augustana) slices against storage-induced oxidative stress and discoloration by using diode laser exposure

Diode laser irradiation is a novel approach applied to preserve the quality of fresh commodities and minimise oxidative processes, including browning in fresh-cut products. The objective of this study was to investigate the efficacy of diode laser treatment in enhancing the quality of celtuce slices during refrigerated storage at 4 °C. The celtuce slices were subjected to a 660 or 450 nm diode laser for 5 min and then stored for 10 d. Both laser treatments hindered the progression of weight loss and firmness increase in the celtuce slices. The use of a 450 nm diode laser effectively prevented the development of browning and preserved the surface colour by inhibiting the increase in a* and overall colour difference values, as compared to other treatments, during storage for 10 d. The diode laser treatment suppressed the increase in oxidative stress by lowering the levels of MDA, H2O2, and O-2 while retaining a high level of DPPH scavenging activity, AsA, and antioxdant enzyme activities, including SOD, CAT, APX, and GR, in comparison to the untreated slices. The treatment enhanced chlorophylls content due to the up-regulation of LsHEMA1 gene and down-regulation of LsNYC1 gene. The treatment also inhibited factors involving enzymatic browning reaction by suppressing PAL activity, total phenols content, PPO activity and LsPPO gene expression. These suggest that the blue diode laser exposure at 450 nm for 5 min is an effective approach hindering oxidative stress and discoloration of celtuce slices during storage.

Inhibitory effect and the involved mechanism of furaneol on enzymatic browning of potatoes

Enzymatic browning is an important issue impacting the shelf life of fresh-cut potatoes. Using browning inhibitors is an effective method to solve the issue. This research aimed to identify novel and safe inhibitors of enzymatic browning. The research first investigated the inhibitory role of furan compounds in enzymatic browning, then explored the anti-browning effect of furaneol and the involved mechanism. Among the eight tested furan compounds classified as flavorings in food additives, seven showed anti-browning effects, of which three demonstrated superior efficacy in delaying browning compared to the others. Based on the efficacy and odor, furaneol as one natural flavor composition of fresh fruit was selected to be further investigated. At 4 °C, control potatoes browned on day 1. However, furaneol at concentrations of 4 and 8 mM prevented the fresh-cut potatoes from browning for up to 10 d, and their anti-browning efficacies reached that of sodium bisulfite. Sensory evaluation showed the treated fresh-cut potatoes exhibited a slight and acceptable sweet aroma, which quickly disappeared after heat cooking. Further research revealed furaneol reduced the activity of polyphenol oxidase (PPO), chelated Cu2+, and acted as a mixed-type inhibitor of PPO with competitive inhibition being the dominant. Circular dichroism analysis indicated furaneol decreased α-helix content, increased the β-fold content, and altered the secondary structure of PPO. Fluorescence quenching data showed furaneol can form complexes with PPO, quench the fluorescence produced by PPO and change its tertiary structure. Molecular docking suggested that furaneol could enter the active center region near copper ions and interact with surrounding amino residues through van der Waals force, pi-alkyl interactions and carbon-hydrogen bonds. Furaneol can also cause the brown pigment colorless to a certain extent. Moreover, furaneol addition also improved the antioxidant capacity of enzymatic browning reaction system. Our study first reported the inhibitory effect of furan compounds on enzymatic browning and furaneol has great potential as an anti-browning inhibitor for fresh-cut produce in future.

Unraveling crop enzymatic browning through integrated omics.

Enzymatic browning reactions, triggered by oxidative stress, significantly compromise the quality of harvested crops during postharvest handling. This has profound implications for the agricultural industry. Recent advances have employed a systematic, multi-omics approach to developing anti-browning treatments, thereby enhancing our understanding of the resistance mechanisms in harvested crops. This review illuminates the current multi-omics strategies, including transcriptomic, proteomic, and metabolomic methods, to elucidate the molecular mechanisms underlying browning. These strategies are pivotal for identifying potential metabolic markers or pathways that could mitigate browning in postharvest systems.

The Effectiveness of Edible Coating Aloe Vera (Aloe vera chinensis L.) in Inhibiting Enzymatic Browning on Sliced Apples

Apple is a fruit that turn brown quickly after being cut. One method to maintain the quality of apples cut is coating the fresh-cut apples with an edible coating. Ediblei coatingi is a thini ilayer that can bei eaten and can keep the iquality ofi the icoated material. Thei study aimed toi determinei the effectiveness of edible coating aloe vera (Aloe vera chinensis L.) in inhibit enzymatic browning reaction. The designii wasi usiing icompletely irandomized idesign. The first factor was the citrus species (Citrus aurantifolia, Citrus hystrix DC, Citrus amblycarpa) iand the secondi factori was thei istorage itime (0, 3, 6 day). Edible coating applied to fresh-cut apples and tested for moisture content, total dissolved solids, weight loss, color, overall appearance, vitamin C and total plate count. Thei resultsi ishowed that aloe vera edible coating with citrus extract was not effective in inhibiting the enzymatic reaction of sliced apples. The type of citrus and storage time was affect the effectiveness of aloe vera edible coating. Citrus amblycarpa extract has a lower water content reduction effect with a water content of 54.51% on the 6th day of storage time and has an effect on the total plate count, that Citrus amblycarpa extract has decreased total plate count in day 6th. Citrus aurantifolia extract gives the effect of maintaining brightness compared to other types of citrus, with a brightness value of 58,290 on the 6th day. The type of citrus has no effect on weight loss, total dissolved solids, overall appearance. The length of storage has an effect on the effectiveness of aloe vera edible coating, the longer it is stored, the apples cut will decrease in quality.

Characterization of Polyphenol Oxidase from Eruca sativa

Enzymatic browning reactions by polyphenol oxidases cause alteration of appearance, flavor and nutritive value of vegetables and fruits. It is one of the important problems for vegetables used as salads and causes lots of economic losses. In this study, polyphenol oxidase (PPO) from Eruca sativa was extracted and characterization studies were carried out. Substrate specificity for variable substrates, optimum pH, optimum temperature, effect of different metal ions were assayed. Km and Vmax values were determined as for pyrocatechol Km = 10.24 mM, Vmax = 0.0018 U min-1, catechin; Km = 12.57 mM, Vmax = 0.0012 U min-1, gallic acid; Km = 23.07 mM, Vmax = 0.0001 U min-1. Optimum pH and temperature were determined as pH:7.0 and 20 oC respectively. Effect of various metal ions such as, K+, Fe2+, Mg2+, Zn2+, Cu2+ and Hg2+ on enzyme activity were measured. K+, Mg2+, Zn2+, Cu2+ ions inhibited PPO activity significantly. However Fe2+ ion did not inhibit PPO activity.

Recent Advances of Polyphenol Oxidases in Plants

Polyphenol oxidase (PPO) is present in most higher plants, but also in animals and fungi. PPO in plants had been summarized several years ago. However, recent advances in studies of PPO in plants are lacking. This review concludes new researches on PPO distribution, structure, molecular weights, optimal temperature, pH, and substrates. And, the transformation of PPO from latent to active state was also discussed. This state shift is a vital reason for elevating PPO activity, but the activation mechanism in plants has not been elucidated. PPO has an important role in plant stress resistance and physiological metabolism. However, the enzymatic browning reaction induced by PPO is a major problem in the production, processing, and storage of fruits and vegetables. Meanwhile, we summarized various new methods that had been invented to decrease enzymatic browning by inhibiting PPO activity. In addition, our manuscript included information on several important biological functions and the transcriptional regulation of PPO in plants. Furthermore, we also prospect some future research areas of PPO and hope they will be useful for future research in plants.

A Genome-Wide View of the Transcriptome Dynamics of Fresh-Cut Potato Tubers.

Fresh fruits and vegetable products are easily perishable during postharvest handling due to enzymatic browning reactions. This phenomenon has contributed to a significant loss of food. To reveal the physiological changes in fresh-cut potato tubers at the molecular level, a transcriptome analysis of potato tubers after cutting was carried out. A total of 10,872, 10,449, and 11,880 differentially expressed genes (DEGs) were identified at 4 h, 12 h and 24 h after cutting, respectively. More than 87.5% of these DEGs were classified into the categories of biological process (BP) and molecular function (MF) based on Gene Ontology (GO) analysis. There was a difference in the response to cutting at different stages after the cutting of potato tubers. The genes related to the phenol and fatty biosynthesis pathways, which are responsible for enzymatic browning and wound healing in potato tubers, were significantly enriched at 0-24 h after cutting. Most genes related to the enzymatic browning of potato tubers were up-regulated in response to cut-wounding. Plant hormone biosynthesis, signal molecular biosynthesis and transduction-related genes, such as gibberelin (GA), cytokinin (CK), ethylene (ET), auxin (IAA), jasmonic acid (JA), salicylic (SA), and Respiratory burst oxidase (Rboh) significantly changed at the early stage after cutting. In addition, the transcription factors involved in the wound response were the most abundant at the early stage after cutting. The transcription factor with the greatest response to injury was MYB, followed by AP2-EREBP, C3H and WRKY. This study revealed the physiological changes at the molecular level of fresh-cut potato tubers after cutting. This information is needed for developing a better approach to enhancing the postharvest shelf life of fresh processed potato and the breeding of potato plants that are resistant to enzymatic browning.

Hydrodynamic cavitation processing of ascorbic acid treated precooled sugarcane juice for physiochemical, bioactive, enzyme stability, and microbial safety

AbstractA hydrodynamic cavitation (HC) system (0.35 MPa) with a cooling arrangement was developed for the treatment of ascorbic acid (AA)‐treated sugarcane juice (AASCJ). The AASCJ was precooled to different temperatures (4, 17, and 30°C) and underwent HC processing for different durations (10, 20, 30, and 40 min). The quality parameters such as pH, total soluble solids, titratable acidity, polyphenol oxidase (PPO), peroxidase (POD) activity, viscosity, total color difference, microbial load, total phenolic, flavonoids, AA, and antioxidant activity were investigated. The processed AASCJ precooled to 4°C resulted in more than 90% retention in color, total phenolic content, flavonoid content, and antioxidant activity. The PPO and POD activities significantly reduced after HC treatment. A 3 log reduction in the microbial population was achieved during HC processing. The optimized condition for HC treatment of AASCJ was a precooling temperature of 4°C and a treatment time of 30 min.Practical applicationsSugarcane juice has a short shelf life due to the high rate of microbiological contamination and enzymatic reactions that occur shortly after extraction. Low‐temperature HC is a nonthermal approach for processing low viscous liquid foods. The HC processed AASCJ is microbiologically safe, with reduced PPO and POD activity, and better retention of bioactive compounds. The low‐temperature HC processing can be used instead of thermal processing to reduce both enzymatic and nonenzymatic browning reactions and eradicate pathogenic microorganisms while maintaining the sugarcane juice quality. This approach is simple to handle, requires little investment, and does not use environmentally hazardous chemicals.

Combined effect of Emblica officinalis juice in the prevention of enzymatic browning in Solanum anguivi L.

Aim: The present study aimed to investigate the impact of Emblica officinalis juice as an antibrowning agent on Solanum anguivi L. juice where enzymatic browning reaction occurs naturally. Methodology: The fresh fruits of S. anguivi (S) and E. officinalis (E) were weighted at five different proportions such as S1-100g:E0-0g; S0-0g:E1-100g; S1-25g:E3-75g; S1-50g:E1-50g and S3-75g:E1-25g. Each combination was ground using a domestic mixer to extract the juice without adding water and analyzed for its characteristics such as color value, browning index, and acceptance level through a sensory evaluation which was recorded at two different intervals (0 and 90 min). Results: Overall color analysis (DE*) indicates that E. officinalis juice significantly reduced the enzymatic browning reaction by its concentration and postponed the brown color development in all three combinations of extracted fruit juices during the storage period. Although, the browning index was high in all the combinations of juices at 0 and 90 mins, except S1-25g:E3-75g, since it had a higher concentration of E. officinalis. The sensory evaluation opted that S1-25g:E3-75g was accepted by all panel members. The FTIR spectral peak revealed the presence of various functional compounds such as carbohydrates, phenol, iron, alkanes, primary amines, esters, aromatics, phosphorous compounds, aliphatic amines, ketones, bromo and halo compounds. Interpretation: The present study demonstrated that the enrichment of S. anguivi juice with E. officinalis concentration had prevented the browning that often occurred due to enzyme catalyst where the reaction of conversion of o-quinones in the presence of oxygen, and o-quinones polymerise into undesirable brown color compound. The developed juice could be used in the formulation of nutraceutical-based ready-to-serve (RTS) beverages that might be the solution for preventing several diseases. Key words: Browning index, Color profile, FTIR spectra, Natural inhibitor, Oxidation, Solanum anguivi

Thermal processes improving antibrowning potential of mixed Aloe vera and pineapple core extract solution on browning inhibition of fresh‐cut apples

SummaryAloe vera and pineapple fruit extract have been applied as natural antibrowning agent for fresh‐cut products. The effect of different thermal treatment processes (high‐temperature–short‐time pasteurisation at 80 ± 1 °C for 15 s and sterilisation at 121 ± 1 °C for 20 min) of mixed A. vera and pineapple core extract solution at a ratio of 1:1 (v/v) (AP) on enzymatic browning control of fresh‐cut ‘Gala’ apples was investigated. Both thermal processes increased the antioxidant activities of AP solution compared to unheated AP solution. Coating of both thermal processed AP solutions alleviated the increased browning incidence of the fresh‐cut apples during storage. Compared to sterilised AP coating, the pasteurised AP coating maintained visual appearance, whiteness index (WI) and L* values as well as inhibited browning incidence due to the prevention of increased a*, b*, ΔE* and browning index (BI) values of fresh‐cut apples during storage. The fresh‐cut apples coated with pasteurised AP had lower total phenolic compounds and polyphenol oxidase activity compared to the samples coated with sterilised AP. These suggested that the suitable thermal process was helpful to enhance antibrowning ability of AP coating agents to control enzymatic browning reaction of fresh‐cut fruits.

Explant Sterilization Technique Castanopsis argentea (Blume) A.DC. with the addition of Ascorbic Acid and Sodium Hypochlorite (NaOCl) In Vitro

Castanopsis argentea (Blume) A.DC. has the local name saninten. This plant is one of the woody plants that has the potential to be developed because it is beneficial for wildlife to nest and is used in reforestation. The seeds of this plant can be used for food by boiling and burning. This plant must be preserved so that it does not become extinct. However, the propagation, so it must use the technique of propagation through tissue culture. This study aims to determine the best sterilization technique for in vitro culture of C. argentea. Eight methods of explant sterilization have been carried out in this study. Methods 1-4 do not use ascorbic acid immersion, while methods 5-8 use the addition of ascorbic acid. Based on observations, it is known that the best sterilization is in the 8th method because the level of contamination and browning is lower than other methods, namely on the fifth day after planting only 20%. The 8th method is graded sterilization. In graded sterilization, explants were gradually immersed in 10% NaOCl, 20% NaOCl, and 30% NaOCl, respectively. Multilevel sterilization is the most effective method of sterilization to reduce contamination and browning. Ascorbic acid acts as an antioxidant and reduces contamination in the enzymatic browning reaction. The combination of sterile substances, time, sequence, and method of immersion affects the sterility of explants.

Melatonin maintained higher contents of unsaturated fatty acid and cell membrane structure integrity in banana peel and alleviated postharvest chilling injury

Exogenous melatonin confers the chilling tolerance of banana fruit by promoting reactive oxygen species (ROS) scavenging system and inducing the unsaturated fatty acid synthesis. The results showed that melatonin treatment increased the contents of phospholipids, promoted the ROS scavenging enzyme, and restrained the activities of lipoxygenase (LOX), and thus reduced the lipid peroxidation of banana peel. In addition, melatonin treatment increased the flavonoids and proline contents, which was conducive to antioxidant capacity. Interestingly, the enhanced antioxidant capacity is conducive to the stability of unsaturated fatty acids and reduce the enzymatic browning reaction. Moreover, melatonin treatment induced the expression of omega-3/6 fatty acid desaturase and triggered the fatty acid metabolism activity, by which maintained higher contents of unsaturated fatty acid in banana peel. Moreover, melatonin treatment stimulated the accumulation of fatty acids in banana peel, and was involved in alleviating fruit chilling injury.

Recent advances on the stability of dietary polyphenols

Recent advances on the stability of dietary polyphenols

The Physicochemical Properties, Volatile Compounds and Taste Profile of Black Garlic (Allium sativum L.) Cloves, Paste and Powder

Black garlic is produced as a result of the so-called “fermentation processes” of whole heads or cloves kept under controlled conditions of temperature and humidity for several weeks. During this long-term heat treatment, garlic undergoes enzymatic and non-enzymatic browning reactions, which greatly change its taste, aroma, physicochemical, organoleptic and bioactive properties. Black garlic is most often produced in the form of cloves, and recently also in the form of paste and powder. This work focused on the comparison of functional properties of black garlic, such as volatile compounds, taste profile, total polyphenols content, antioxidant activity, color (CIE L*, a*, b*), water activity (aw), pH, soluble solids content (°Brix) and moisture content, depending on the form of its occurrence: cloves, spreading paste and powder. After long-term heat treatment, garlic was characterized by a higher content of dry matter and water-soluble solids, respectively at about 22% and 24% for spreading paste and 166% and 44% for powder. The conducted research showed significant differences in the bioactive properties of the tested garlic samples, with the lowest content of polyphenols and antioxidant properties in fresh, unprocessed garlic (6.05 ± 0.07 mg GAE/1 g d.m. and 232.95 ± 4.06 µM TEAC/1 g d.m., respectively), while in garlic subjected to long-term heat treatment, the total polyphenols content and antioxidant potential were two times higher than in the unprocessed garlic. The polyphenol content and antioxidant properties were the highest in the spread garlic (respectively, 15.16 ± 0.08 mg GAE/1 g d.m. and 638.46 ± 3.37 µM TEAC/1 g d.m.) and the lowest in the powdered samples (respectively, 11.02 ± 0.51 mg GAE/1 g d.m. and 541.71 ± 5.22 µM TEAC/1 g d.m.). Obtained black garlic samples gain completely different sensory characteristics determined using instrumental methods. In black garlic and its preparations, the intensity of unpleasant taste and aroma is reduced as a result of the appearance of metabolites during the long-term heat treatment, which in turn determined the specific, delicate sweet–sour taste and pleasant aroma, completely unrelated to the aroma of the unprocessed product. Taking into account the obtained results, it can be stated that black garlic, in the form of cloves, paste and powder, exhibits completely different properties than white garlic.

Development of Ozonated Water Technology to Inhibit Enzymatic Browning of “Mang-Koot-Cut”

This work aim to produce high-concentration ozonated water using a dielectric barrier discharge for inhibiting the enzymatic browning of Mang-Koot-Cut. The ozonizer was composed of radio frequency (RF) powered mesh electrode and grounded water electrode that sandwiched a Pyrex glass tube as the dielectric material. The discharge of air flowing through the ozonizer generated ozone gas. The optimal flow rate was 2 L/min. A venturi injector caused an effective mixing between ozone gas and water to obtain ozonated water. The RF power, discharge time and airflow rate controlled the dissolved ozone concentration. Ozonated water with dissolved ozone concentrations greater than 0.2 ppm could reduce the browning reaction of Mang-Koot-Cut. Measurement of the color values L*, a* and b* showed that ozonated water could delay the browning of Mang-Koot-Cut. The results exhibited the possibility of using ozonated water to reduce the browning activity in Mang-Koot-Cut as a substitute for chemicals that are harmful to health. Ozonated water is green chemistry with no toxic residues.
 HIGHLIGHTS
 
 The developed ozonated water production system can generate a concentration of about 0.3 ppm
 Ozonated water can inhibit the enzymatic browning reaction caused by the PPO enzyme and phenol compounds
 
 GRAPHICAL ABSTRACT

Prevention of Enzymatic Browning by Natural Extracts and Genome-Editing: A Review on Recent Progress.

Fresh fruits and vegetable products are easily perishable during postharvest handling due to enzymatic browning reactions. This phenomenon has contributed to a significant loss of food quality and appearance. Thus, a safe and effective alternative method from natural sources is needed to tackle enzymatic browning prevention. The capabilities of natural anti-browning agents derived from plant- and animal-based resources in inhibiting enzymatic activity have been demonstrated in the literature. Some also possess strong antioxidants properties. This review aims to summarize a recent investigation regarding the use of natural anti-browning extracts from different sources for controlling the browning. The potential applications of genome-editing in preventing browning activity and improving postharvest quality is also discussed. Moreover, the patents on the anti-browning extract from natural sources is also presented in this review. The information reviewed here could provide new insights, contributing to the development of natural anti-browning extracts and genome-editing techniques for the prevention of food browning.

Benzothiazines as Major Intermediates in Enzymatic Browning Reactions of Catechin and Cysteine.

The course of melanin formation is yet not thoroughly resolved on a mechanistic level. With the present study, incubations of catechin (CA)- and cysteine-derived dihydro-1,4-benzothiazine carboxylic acid derivatives were investigated for colored products during enzymatic browning. Analyses by high-performance liquid chromatography (HPLC)-mass spectrometry revealed the formation of two novel decarboxylated dihydro-1,4-benzothiazine derivatives [8-(3,5,7-trihydroxy-3,4-dihydro-2H-chromen-2-yl)-5-hydroxy-3,4-dihydro-2H-benzothiazine and 7-(3,5,7-trihydroxy-3,4-dihydro-2H-chromen-2-yl)-5-hydroxy-3,4-dihydro-2H-benzothiazine] preferentially under acidic conditions. Furthermore, in model reactions under neutral pH, a colored phenazine dimer intermediate was isolated by high-performance countercurrent chromatography and preparative HPLC when conducting the incubations in the presence of o-phenylenediamine (OPD). Mass spectrometry and nuclear magnetic resonance spectroscopy unequivocally verified the structure as (12E)-5,5'-dioxo-11a,11a'-bis(3,5,7-trihydroxy-3,4-dihydro-2H-chromen-2-yl)-3,3',4,4',5a,5a',6,6',11,11',11a,11a'-dodecahydro-2H,2'H,5H,5'H-12,12'-bi[1,4]thiazino[2,3-b]phenazine-3,3'-dicarboxylic acid. Enzymatically catalyzed incubations under aeration starting from the initial CA-cysteine adducts and their follow-up dihydro-1,4-benzothiazine carboxylic acids, respectively, proved that the unstable colored compound was a trichochrome-like reaction intermediate of the browning reaction cascade which can be trapped by postincubation with OPD, thus verifying their direct mechanistic relationship.

EFFECT OF BOILING TIME AND STORAGE CONDITION (FROZEN AND UNFROZEN) ON THE PHYSICO-CHEMICAL PROPERTIES OF FLACOURTIA JANGOMAS (LOUR) RAUESCH FRUIT

Flacourtia jangomas, locally known as Seriales is an indigenous fruit tree in the Philippines. It potentially contains important nutrients and bioactive compounds, but it is a less known commodity, with no economic value. Moreover, the fruit is highly prone to enzymatic browning reaction, resulting to undesirable discoloration once exposed to air. Hence, this study was conducted to determine the changes in the physico-chemical properties of ripe Seriales fruit as affected by boiling time and storage conditions. Ripe Seriales fruits of known weight were exposed to upto 10 minutes of boiling water. Representative samples from each treatment were analysed of its color, total soluble solids, pH, and % titratable acidity. The same procedures were done to samples that had been stored for 19 days in the freezer. The results of the experiment revealed that storage conditions (frozen and not frozen) only affected the b* of the skin of the ripe Seriales fruits, while boiling time affected all other parameters, excepts pH, %TTA, and b* values of the fruit flesh.