No abstract

Hot water treatment (HT) has proved to alleviate chilling injury (CI) in bell pepper and other Solanaceae species, this has been associated with the presence of metabolites such as sugars and polyamines, which protect the plasmatic membrane. However, it is unknown if the phenolic compounds in bell pepper play a role in the CI tolerance induced by the application of a HT. The aim of this study was to identify the specific phenolics associated with induced CI tolerance in bell pepper by HT (53 °C, 1 to 3 min). Fruit treated for 1 min (HT‐1 min) exhibited CI tolerance (the lowest symptom development, electrolyte leakage, and vitamin C loss) and was the chosen treatment for further experiments. The phenolic composition was affected by HT‐1 min and CI. Phenolics presented a strong correlation with the antioxidant activity. In fruit with CI tolerance, the concentration of seven compounds was increased, being quercetin‐O‐rhamnoside‐O‐hexoside and chlorogenic acid the most remarkable. Quercetin‐3‐O‐rhamnoside was accumulated only in fruit with induced tolerance, meanwhile orientin was particularly sensitive to heat and cold exposure. Thus, HT‐1 min (53 °C, 1 min) is a useful technology to induce CI tolerance in bell pepper and such tolerance is associated with the phenolic composition that may reduce the prevalence of oxidative stress during the storage under CI conditions.Practical ApplicationPhenolics induced by CI and HT may be useful to detect early stages of heat and chilling injuries in bell pepper and prevent the negative effect of such stresses even before its harvest and during commercial storage. Additionally, the phenolics associated with CI tolerance may be used as markers in breeding programs to create new chilling resistant cultivars.

The application of technologies to reduce papaya (Carica papaya L.) anthracnose, a disease caused by the fungus Colletotrichum gloeosporioides, most of the time results in a loss of nutrients and other bioactive compounds. This study was performed to determine the effect of hot water (HW; 48°C/20 min), calcium chloride (Ca; 1%/20 min), and their combination (HW‐Ca) in bioactive compounds and antioxidant activity of papaya inoculated with Colletotrichum gloeosporioides stored during 20 days at 12°C. HW‐Ca treated fruits showed higher ascorbic acid, phenolics content, and antioxidant activity than untreated and HW and Ca treated fruit, which correlated with the contents of ascorbic acid, phenolics, and β‐cryptoxanthin. Also, HW‐Ca treatment resulted in fruits showing lower decay area, greater firmness and color retention. The results suggest that HW‐Ca treatment could be used to reach higher antioxidant activity values and to preserve the postharvest quality parameters, whereas the development of anthracnose symptoms was delayed. Practical applications Papaya infected by Colletotrichum gloeosporioides and treated with hot water (HW) in combination with calcium chloride (Ca) had a good firmness, color retention, and higher antioxidant activity and content of ascorbic acid and phenolics, while the development of anthracnose symptoms was delayed. In this sense, the proposed HW‐Ca treatment of papaya is a strategy to protect against Colletotrichum gloeosporioides and to obtain fruits with good quality, resulting in an interesting postharvest alternative to the application of fungicides.

No abstract

BACKGROUND: Colletotrichum gloeosporioides causes anthracnose in a large number of crops. Synthetic fungicides are employed to prevent this disease, even though their effectiveness and safety is questionable. Thus, effective and innocuous antifungal compounds are proposed as natural alternatives against anthracnose. The hexane fraction of Vitex mollis pulp (HF-VM) reduces anthracnose incidence in papaya fruit; however, the active compounds and antifungal mechanism of HF-VM are unknown. The aims of this study were to characterize the activity of HF-VM sub-fractions (sHF 1 -sHF 7 ) against a thiabendazole-resistant Colletotrichum gloeosporioides strain, identify the chemical components and investigate the mechanism of the most active sub-fraction. RESULTS: The sHF 3 showed the highest inhibitory activity against Colletotrichum gloeosporioides with a minimal inhibitory concentration (MIC) of 0.5 mg mL −1 , whereas thiabendazole (TBZ) had a MIC value higher than 2 mg mL −1 . The gas chromatography-mass spectrometry (GC-MS) analysis showed that the compounds in sHF 3 were methyl 4-decenoate, caprylic acid, and 24-methylencycloartanol. These compounds are rarely found in fruits and are reported for the first time on Vitex species. The purified 24-methylencycloartanol was inactive (MIC > 0.5 mg mL −1 ). In contrast, the commercial standard of caprylic acid presented an elevated activity (MIC = 0.125 mg mL −1 ), indicating that this compound is the main one responsible for the antifungal properties of sHF 3 . Furthermore, the sHF 3 inhibited the spore germination and induced membrane disruption in both the spore and mycelium of Colletotrichum gloeosporioides.CONCLUSION: Vitex mollis fruit is a novel source of antifungal caprylic acid that could be employed as a marker to prepare standardized extracts with antifungal properties.

Chitosan (Ch) is a biopolymer with excellent antimicrobial and antioxidant properties, capable of maintaining the organoleptic quality of fruits. These properties have been related to its molecular weight. However, the effect of different molecular weights on the non‐enzymatic antioxidant system and postharvest quality of anthracnose‐infected papaya is still unknown. Therefore, this study evaluated the effect of different Ch molecular weights (13, 25, and 55 kDa) on anthracnose development, antioxidant capacity, and postharvest quality of papaya. The Ch‐55, Ch‐25, and 13 kDa inhibited the development of Colletotrichum gloeosporioides. In comparison with thiabendazole, Ch with different molecular weights showed fungicidal effects. Ch‐55 kDa reduced anthracnose incidence and severity and maintained postharvest quality parameters of papaya. In addition, Ch‐55 and Ch‐13 kDa favored synthesis of ascorbic acid, total phenolics, and antioxidant capacity. Therefore, Ch‐55 kDa is an alternative to the protection against C. gloeosporioides and a stimulant of the non‐enzymatic antioxidant system in papaya fruits during its postharvest storage. Practical Application Ch with different molecular weights have different effects over anthracnose control and postharvest quality in papaya. In addition, they have different stimulation levels on the non‐enzymatic antioxidant system of papaya fruits, in a higher level than the chemical fungicide TBZ, by regulating the growth of the fungus and the degradative processes that are generated in fungal infection. In this sense, we believe that our findings could be of interest for producers and farmers to take advantage of this biopolymer to control anthracnose, preserve the postharvest quality, and stimulate the non‐enzymatic antioxidant system of papaya fruit.

Hot water treatment (HT) induces chilling injury (CI) tolerance in mango, but prolonged exposure to HT causes softening. In this sense, calcium salts stabilize the cell wall. Nevertheless, there is little information on the effect of HT combined with calcium salts (HT‐Ca) on calcium absorption and cell wall stability during storage of mango at CI temperature. We evaluated the effect of quarantine HT in combination with calcium chloride (CaCl2), calcium citrate (CaCit), or calcium lactate (CaLac) on calcium absorption, CI tolerance, and cell wall stabilization. HT and HT‐CaCl2 had the lowest CI development. HT increased firmness loss and electrolyte leakage, and HT‐Ca counteracted this effect. Overall, HT‐Ca treatments had a similar effect on the cell wall degrading enzymes. HT‐CaCl2 was the best treatment and did not present alterations on the epicuticular wax as observed on HT. HT‐CaCl2 is a useful technology to stabilize cell wall and preserve mango during chilling storage. Practical applications The addition of calcium salts in an established hot water quarantine procedure for mango exportation represents a viable alternative to counteract the negative effects of this thermal treatment upon cell microstructure, maintaining its positive effect of tolerance to chilling injury. In this sense, mango producers and packers can use a HT‐CaCl2 treatment to reduce the presence of chilling injury and extent the fruit shelf life and improve its commercialization. Furthermore, technical and infrastructure changes are not necessary for the packaging chain.