Aníbal O. Herrera

Respiration and ethylene generation modeling of “Hass” avocado and feijoa fruits and application in modified atmosphere packaging

ABSTRACT A proper description of the respiration and ethylene generation is important in the development of package systems for the preservation of fresh fruits and vegetables. In this work, a model based on both Michaelis-Menten and chemical kinetics equations was developed and assessed in order to describe the respiration and ethylene generation of avocado (Persea americana cv. Hass) and feijoa fruits (Acca sellowiana Berg) from experimental data obtained at different temperatures by a closed system method. The temperature effect in both processes was described using Arrhenius-type relationships. After this, avocadoes and feijoas were packed in perforated low-density polyethylene (LDPE) and polypropylene (PP) bags for 8 days at 12°C and 80% RH to validate the usefulness of the model to describe the gas evolution in modified atmosphere packaging (MAP). For avocado fruits, respiration rates of 2680-3030 cm3 kg-1 d-1 were obtained at 24 °C and normal atmosphere, and 3650-4230 cm3 kg-1 d-1 for feijoa fruits. As for ethylene production rates, at 24 °C were obtained values of 3.11 cm3 kg-1 d-1 for avocado and 0.50 cm3 kg-1 d-1 for feijoa. At 6 °C, respiration and ethylene production rates were up to 6 times lower. It was possible to describe properly the ethylene generation using a Michaelis-Menten simple equation and the respiration rates using a Michaelis-Menten uncompetitive kinetics for both fruits with coefficients of determination above 0.9 in each case. The overall model was validated in the MAP test being possible to predict successfully the O2, CO2 and C2H4 levels inside the packages.

Cinética de Inactivación de la Enzima Peroxidasa, Color y Textura en Papa Criolla (Solanum tuberosum Grupo phureja) sometida a tres Condiciones de Escaldado

The objective of this work was to determine the inactivation kinetics of peroxidase enzyme and the change in color and texture in golden potato tubers (Solanum tuberosum phureja group) exposed to blanching with water at 80°C, 90°C and to saturated steam at 93°C. The heat transfer coefficients for the blanch water ranged between 214 and 230 W °C -1 m -2 while for saturated steam they showed an average of 84.5 W °C -1 m -2 . At different pre-cooking times the golden potato tuber showed an area that developed enzymatic browning, which was fitted to the Michaelis-Menten kinetic model and another area where the color change decreased due to enzyme inactivation, which corresponded to first order kinetics, in a similar way as the texture behavior. The inactivation of peroxidase enzyme followed the Lumry-Eyring mechanism.

Effect of ethylene and 1-methylcyclopropene on the postharvest behavior of cape gooseberry fruits (Physalis peruviana L.)

Cape gooseberry (Physalis peruviana L.) fruits are highly perishable berries that exhibit a climacteric respiratory behavior. The objective of this study was to evaluate the effect of ethylene and the ethylene action inhibitor 1-methylcyclopropene on the postharvest behavior of cape gooseberry fruits (ecotype Colombia). Fruits were treated with ethylene, in an ethephon application (1000 µL L−1), and pretreated with 1-methylcyclopropene (1 µL L−1), 1-methylcyclopropene+ethylene, and results compared with a control without application. Subsequently, the fruits were maintained at room temperature (20 ℃, 75% RH) for up to 11 days. The pretreatment of the cape gooseberry fruits with 1-methylcyclopropene delayed most of the ripening-associated parameters, with a reduction in the respiration rate and ethylene production, skin color development, total soluble solids, total carotenoid content, loss of firmness, loss of total titratable acidity and emission of volatile compounds such as ethyl octanoate, ethyl butanoate, ethyl decanoate, and hexyl decanoate. Conversely, application of ethephon accelerated most of these physiological changes and also overcame most of the effects prevented by the ethylene action inhibitor. Altogether, the results supported the idea of a climacteric-like behavior for cape gooseberry fruits and pointing out that the pretreatment with 1-methylcyclopropene may be a promising and efficient postharvest treatment to delay maturity and extend the postharvest period.

Methyl Jasmonate, a Degreening Alternative for Mandarin (Citrus Reticulata L.) Var. Arrayana Fruits

Mandarin accounts for a significant part of the Colombian citrus fruit production, the postharvest degreening of these products to attain pigmentation being a common practice when they are harvested in the tropics. The endogenous signaling molecules such as methyl jasmonate and ethylene are produced during fruit formation, and they play a key role in postharvest and stress responses. The latter is commonly used to degreen mandarin, which, however, exhibits low sensitivity to this compound. It is therefore important to establish degreening alternatives to ethylene. Thus, the aim of this study was to determine the effect of methyl jasmonate on the degreening of Arrayana mandarin (Citrus reticulata L.). For such purpose, respiration rate, weight loss, color index, total chlorophyll, total soluble solids, firmness and total acidity were determined. The treatments applied were: methyl jasmonate (MeJA) 1 μM 24h, Ethylene (ET) 1000 ppm 20 min, 1-methylcyclopropene (1-MCP) 0.5 μL L 2h; and the combinations 1-MCP + MeJA, 1MCP + ET. Generally obtained with the MeJA and 1-MCP + MeJA treatments, the most significant results took place at 14 days after treatment implementation (DATI) for total titratable acidity, and at 4 DATI for total chlorophyll and color index. The TSS/acid ratio (maturity ratio) became constant since 7 DATI under the MeJA treatment. Thus, the use of MeJA after 1-MCP pretreatment comes to be an interesting degreening option, all the more when considering that these physiological responses have not been reported in previous studies.

Simulation Of An Active Packaging With Catalytic Oxidation Of Ethylene For 'Cavendish' Banana

In the ripening and senescence of fruits, ethylene plays a major role and therefore, its control is essential to extend the shelf-life of these products. In this study, the kinetics of catalytic oxidation of ethylene was experimentally determined for a catalyst of gold nanoparticles supported on cerium oxides and the use of this was simulated in a perforated rigid packaging system for ‘Cavendish’ bananas. According to the simulations performed, for 1 kg of fruit in the active packaging 5.931 g of the obtained catalyst are needed to reduce 99% of the ethylene concentration at 12°C and with constant concentrations of 0.072 of O 2 and 0.178 of CO 2 (in molar fraction).