Characterization of alcohol acetyltransferases in the ripe flesh of 'Monthong' and 'Chanthaburi 1' durians.

Durian is economically significant in Southeast Asia due to its distinctive aroma and palatability. During fruit ripening, the flesh generates a substantial quantity of esters and some sulfur-containing compounds. This study aimed to analyze the ester profiles and characteristics of alcohol acetyltransferase (AAT; EC. 2.3.1.84) in the ripe flesh of two Thai durian (Durio zibethinus Merr.) cultivars, 'Chanthaburi 1' (a hybrid cultivar with a soft aroma) and 'Monthong' (a renowned cultivar with a medium scent). The primary esters responsible for the aromatic compounds found in durian are ethyl-2-methyl butanoate, ethyl hexanoate, and ethyl octanoate. The AAT's efficacy was assessed in its ability to catalyze the synthesis of acetate esters through the reaction between acetyl CoA and different alcohols. The AAT enzymes extracted from 'Chanthaburi 1' and 'Monthong' cultivars exhibited a notable affinity towards 3-methyl-1-butanol and hexanol as alcohol substrates. Propanol and butanol exhibited moderate activity as AAT substrates, whereas methanol and ethanol demonstrated the lowest. Both durians exhibited favorable enzyme activity at a temperature of 30 °C. However, 'Monthong' AAT demonstrated superior performance across a broader pH range compared to 'Chanthaburi 1' AAT. The partially purified proteins precipitated with ammonium sulfate and subsequently gel-filtered through a DEAE-Sephadex® column enhanced the potency of 'Chanthaburi 1' AAT, resulting in increased purity (1.20-fold) and specificity (1.08-fold) compared to 'Monthong'. The AAT of 'Chanthaburi 1' and 'Monthong' exhibited molecular weights of 39.52 and 41.51 kDa, respectively. This study presents the initial documentation of AAT in durians through an enzyme assay and activity staining technique.

Terpenoids and Bio-Functions of Essential Oils Hydrodistilled Differently from Freshly Immature and Mature Blumea balsamifera Leaves.

The volatiles and antioxidant capacity of essential oils (EOs) extracted from freshly immature and mature leaves of Blumea balsamifera at various hydrodistillation times were investigated. Seven major terpenoids were identified: two monoterpenes, camphor and L-borneol, and five sesquiterpenes, silphiperfol-5-ene, 7-epi-silphiperfol-5-ene, ß-caryophyllene, ɤ-eudesmol, and α-eudesmol. The quantity and terpenoid composition of the EOs were impressed by leaf maturity and hydrodistillation times. The yield of EOs from the immature leaves was 1.4 times that of mature leaves, with 73% of the yield acquired within the first 6 hours (hrs) of hydrodistillation. Approximately 97% of camphor and L-borneol, 80% of ß-caryophyllene, silphiperfolene, and 7-epi-silphiperfolene, 32% of ɤ-eudesmol, and 54% α-eudesmol were collected in the first 6 hrs of hydrodistillation. More ß-caryophyllene, ɤ-eudesmol, and α-eudesmol were found in the mature leaf EOs. The antioxidant capacity of the EOs was proportionally related to their terpenoid contents. The EOs extracted from immature leaves at 0-6 hrs of hydrodistillation demonstrated distinctive antibacterial activity against Staphylococcus aureus, with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 0.5 mg/mL and 1 mg/mL, respectively.

Phenolics, Antioxidant and Antibacterial Activities of Immature and Mature Blumea balsamifera Leaf Extracts Eluted with Different Solvents.

Blumea balsamifera (L.) DC., belonging to the Asteraceae family, also known as "ngai camphor," is one of the traditional herbs used in Thailand for folk medicine and a component in local food and drinks. There was, however, no evidence indicating the presence of beneficial compounds at different leaf ages. Exploring various extraction solvents, we investigated the phenolics, flavonoids in particular quercetin content, antioxidant capacity, and antibacterial activity of immature and mature leaf extracts. The dried leaves were macerated in 50% ethanol, 95% ethanol, hexane, or decocted in water. Bioactive substances were analyzed by UV spectrophotometry and HPLC. Analysis of antioxidant capacity was done byDPPH, ABTS, FRAP, and NO scavenging assays. The antibacterial activity of immature leaf extract eluted with 50% ethanol was subsequentially evaluated in vitro. Extraction with 50% ethanol proved optimal, yielding 1.2-1.6-fold and 1.5-fold greater immature and mature leaf extracts than other solvents. More phenolics (1.2-fold), flavonoids (1.1-fold), quercetin content (4.8-fold), and antioxidant activity (1.3-fold) were found in the immature leaf extract. There was a significant positive correlation between antioxidant activity and bioactive compounds. The immature leaf extract eluted with 50% ethanol showed antibacterial activity against Staphylococcus aureus, with a minimum inhibitory concentration of 0.5 mg/mL. The immature leaves of B. balsamifera are a rich source of quercetin and phenolics, and 50% ethanol proved optimal for extracting bioactive components from these leaves.

Synergistic effect of vacuum packaging and cold shock reduce lignification of asparagus.

This study was carried out to investigate the combined effects of vacuum packaging (VP) and cold shock (CS) of asparagus on lignification during storage at 4°C. Physiological and biochemical changes were analyzed. The VP + CS treatment reduced fresh weight loss and color change and prevented the increment of spear toughness the most compared to VP, CS, and control. Also, the VP + CS was most effective in suppressing the activities of lignin biosynthesis enzymes, including phenylalanine ammonia-lyase, cinnamyl-alcohol dehydrogenase, and peroxidase, thereby delaying lignin formation. In addition, the combined treatment delayed ethylene production peak and the reduction of total phenolic content. These results suggest that VP + CS may maintain eating quality of asparagus spears through delay of lignification. PRACTICAL APPLICATIONS: This study mainly focused on reducing lignification of asparagus spears using VP + CS, which is safe, eco-friendly, affordable, and practical. Our results showed that VP + CS significantly delayed lignification. Thus, VP + CS represents a promising postharvest handling approach for reducing the lignin content of asparagus, to preserve its integrity, and improve stability during shipment. This prospective technique will eliminate the use of chemical alternatives to prolong the storage life and maintain the quality of spears.

Efficiency of salicylic acid or methyl jasmonate immersions on internal browning alleviation and physicochemical quality of Queen pineapple cv. "Sawi" fruit during cold storage.

The pineapples were dipped in salicylic acid (SA) (2.5 or 5.0 mM) or methyl jasmonate (MeJA) (0.01 or 0.1 mM) for 1, 2, or 3 hr and then held at 13 ± 1°C for 10 days. The parameters were determined after left the fruits at 25°C for 2 days. It was found that, in the tissue adjacent to the core, 5.0 mM SA for 2 hr and 0.01 mM MeJA for 3 hr alleviated chilling injury (CI) and maintained color than other treatments. The MeJA immersions lowered CI score, electrolyte leakage, and malondialdehyde content greater than other treatments. SA and MeJA immersions retarded polyphenol oxidase activity, total phenols, and induced antioxidant activity during storage. In the pulp tissue, SA treatment increased ascorbic acid and total sugar contents, and MeJA immersions enhanced bioactive compound and antioxidant enzyme activities than SA immersion. Therefore, MeJA immersions could alleviate CI and enhance antioxidant better than other treatments of pineapples during cold storage. PRACTICAL APPLICATIONS: Postharvest immersion at the optimum concentration of SA or MeJA can be applied for commercial scale in order to alleviate chilling of "Sawi" pineapple fruit during storage. MeJA treatment enhances antioxidant activity and reduces internal browning better than SA treatment in pineapple.

Ethylene Induces a Rapid Degradation of Petal Anthocyanins in Cut Vanda 'Sansai Blue' Orchid Flowers.

Ethylene plays a major role in the regulation of flower senescence, including in the ethylene-sensitive Vanda 'Sansai Blue' orchid flowers. This cut flower is popular in Thailand due to its light blue big size florets possessing a beautiful shape pattern. In the present study, we further examined the rapid ethylene-induced process of active anthocyanin degradation in cut Vanda 'Sansai Blue' flowers, which occurred much before detection of other typical senescence-related symptoms. For this purpose, the cut inflorescences were exposed to air (control), 1 or 10 µl L-1 ethylene for 24 h, or to 0.2 µl L-1 1-methylcyclopropene (1-MCP) for 6 h followed by 10 µl L-1 ethylene for 24 h at 21°C, and the effects of these treatments on various parameters were assayed. While the fading-induced effect of ethylene was not concentration-dependent in this range, the ethylene treatment significantly reduced the flower vase life in a concentration-dependent manner, further confirming the separation of the bleaching process from senescence. Exposure of the inflorescences to 1-MCP pre-treatment followed by 10 µl L-1 ethylene, recovered both inflorescence color and anthocyanin content to control levels. Quantification of total anthocyanin content, performed by HPLC analysis on the basis of cyanidin-3-glocuside equivalents, showed that ethylene reduced and 1-MCP recovered the anthocyanins profile in non-hydrolyzed anthocyanin samples of Vanda 'Sansai Blue' florets, assayed at half bloom and bloom developmental stages. The results showed that the ethylene-induced color fading, observed immediately after treatment, resulted from a significant reduction in the levels of the two main anthocyanidins, cyanidin and delphinidin, as well as of other anthocyanidins present in low abundance, but not from changes in the levels of flavonols, such as kaempferol. This anthocyanin degradation process seems to operate via ethylene-increased peroxidase activity, detected at the bud stage. Taken together, our results suggest that the ethylene-induced rapid color bleaching in petals of cut Vanda 'Sansai Blue' flowers is an outcome of in-planta anthocyanin degradation, partially mediated by increased peroxidase activity, and proceeds independently of the flower senescence process.

Influence of roasting on chemical profile, antioxidant and antibacterial activities of dried chili.

Roasted dried chili, used to improve texture and taste, is important for various cuisines. The effect of roasting at 90 °C for 25 min on the chemical profile and bioactivities of dried chili extracted by petroleum ether was investigated. Based on GC-MS analysis, the crude extracts of roasted dried chili exhibited different chemical profile compared to the control. Roasting of dried chili significantly increased total phenolic compounds. Consequently, the antioxidant activity indicated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity and ferric reducing antioxidant power (FRAP) significantly improved. Conversely, a reduction in the antibacterial agents, capsaicin (32.36%) and dihydrocapsaicin (9.11%), in the roasted sample resulted to a decline in antibacterial activity. The extracts showed a strong activity against Bacillus cereus followed by B. subtilis, and Staphylococcus aureus compared to Escherichia coli based on the results of agar disk diffusion, minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC), and electron scanning microscopy observation.

Effect of harvest seasonal and gamma irradiation on the physicochemical changes in pineapple fruit cv. Pattavia during stimulated sea shipment.

Gamma irradiation is used as a phytosanitary treatment for tropical fresh fruit from some producing countries. An experiment was carried out to study the effect of gamma irradiation and season of harvest on the quality 'Pattavia' pineapple fruit. Fruit harvested in the summer and the rainy cool (winter) seasons were exposed to gamma radiation at dose levels of 0 and 400-600 Gy from a 60 Cobalt source and the fruit stored at 13°C and 90% RH for up to 21 days. Gamma irradiation did not affect the ratio of TSS/TA, antioxidant content, or ascorbic acid concentration. However, gamma irradiation did delay color development and also induced internal browning over 50% of flesh discolored in fruit stored for 14 days, especially harvested winter fruit. Moreover, harvesting fruit in different seasons had a significant effect on fruit quality after harvest and during stimulated sea shipment storage. The result showed that gamma irradiation can be used as a phytosanitary treatment with minor changes in eating quality. However, the internal browning was greater if fruit were stored longer than 1 week at 13°C.

Molecular and biochemical characteristics of a gene encoding an alcohol acyl-transferase involved in the generation of aroma volatile esters during melon ripening.

Two genes (CM-AAT1 and CM-AAT2) with strong sequence homology (87% identity at the protein level) putatively involved in the formation of aroma volatile esters have been isolated from Charentais melon fruit. They belong to a large and highly divergent family of multifunctional plant acyl-transferases and show at most 21% identity to the only other fruit acyl-transferase characterized so far in strawberry. RT-PCR studies indicated that both genes were specifically expressed in fruit at increasing rates in the early and mid phases of ripening. Expression was severely reduced in ethylene-suppressed antisense ACC oxidase (AS) fruit and in wild-type (WT) fruit treated with the ethylene antagonist 1-MCP. Cloning of the two genes in yeast revealed that the CM-AAT1 protein exhibited alcohol acyl-transferase activity while no such activity could be detected for CM-AAT2 despite the strong homology between the two sequences. CM-AAT1 was capable of producing esters from a wide range of combinations of alcohols and acyl-CoAs. The higher the carbon chain of aliphatic alcohols, the higher the activity. Branched alcohols were esterified at differential rates depending on the position of the methyl group and the nature of the acyl donor. Phenyl and benzoyl alcohols were also good substrates, but activity varied with the position and size of the aromatic residue. The cis/trans configuration influenced activity either positively (2-hexenol) or negatively (3-hexenol). Because ripening melons evolve the whole range of esters generated by the recombinant CM-AAT1 protein, we conclude that CM-AAT1 plays a major role in aroma volatiles formation in the melon.