Postharvest respiration of fruits and environmental factors interaction: An approach by dynamic regression models

The respiratory metabolism of fruits is affected by multiple internal (product) and external (environmental) factors that often interact with each other. Among the external factors that have the greatest influence on respiration are temperature, air composition, moisture content and illumination. The aim of this paper is to elucidate the influence of environmental factors on the respiration rate of peach fruits based on transfer models obtained by dynamic regression modelling (ARIMAX). The fitted ARIMA models met the criteria of parsimony and white noise in residuals. The estimated coefficients of each model were statistically significant under the Durbin-Watson (DW), Akaike (AIC) and Schwarz (SBC) criteria. Transfer functions revealed 0.15% and 1.9% increase, and 0.001% decrease in the respiration rate of the peach fruit for each unit of change in temperature, relative humidity and illumination of the storage environment, respectively. The respiration rate response took place 1-8 minutes after the change in environmental variables had occurred. It was concluded that the dynamic regression modelling is reliable for predicting the physiological response of fruits the effect of external factors imposed continuously during postharvest handling

Postharvest respiration of fruits and environmental factors interaction: an approach by dynamic regression models

The respiratory metabolism of fruits is affected by multiple internal (product) and external (environmental) factors that often interact with each other. Among the external factors that have the greatest influence on respiration are temperature, air composition, moisture content and illumination. The aim of this paper is to elucidate the influence of environmental factors on the respiration rate of peach fruits based on transfer models obtained by dynamic regression modelling (ARIMAX). The fitted ARIMA models met the criteria of parsimony and white noise in residuals. The estimated coefficients of each model were statistically significant under the Durbin-Watson (DW), Akaike (AIC) and Schwarz (SBC) criteria. Transfer functions revealed 0.15% and 1.9% increase, and 0.001% decrease in the respiration rate of the peach fruit for each unit of change in temperature, relative humidity and illumination of the storage environment, respectively. The respiration rate response took place 1-8 minutes after the change in environmental variables had occurred. It was concluded that the dynamic regression modelling is reliable for predicting the physiological response of fruits the effect of external factors imposed continuously during postharvest handling

Resistencia a ruptura y calidad fisiológica en semillas de maíz bajo compresión axial

The physical, physiological and sanitary qualities of corn seeds are reduced due to the mechanical damage caused by the mechanization of the production process. Knowing the strength and displacement critical values according to the type of endosperm will help decrease the damage during the cleaning, drying, storing and handling processes. This study assessed the strength and displacement from compression, the visible damage and the physiological quality of corn seeds from the following varieties: Cacahuacintle (floury), HS-2 (semi-floury) and Popcorn (hard) considering a humidity of 12 and 20%. The percentage of soft endosperm in Cacahuacintle, HS-2 and Popcorn was 76.20, 33.43 and 15.27%, respectively, while the percentage of hard endosperm was 5.25, 48.93 and 65.21%, respectively. The displacement and the strength for the Cacahuacintle variety was 0.8264 mm and 274.71 N, for the HS-2 variety was 0.5499 mm and 309.07 N and for the Popcorn variety was 0.5066 mm and 356.29 N, while for 12 and 20% humidity it was 0.3279 mm and 312.52 N and 0.9520 mm and 313.81 N, respectively. The damage indexes in compressed seeds were 276.67, 327.78 and 220.01 for Cacahuacintle, HS-2 and Popcorn, respectively, while for uncompressed seeds (control group) the damage indexes were 0.00. Germination was 85.20% for uncompressed seeds and 55% for those seeds subjected to fracture. The damage index was affected by the variety and the compression, but not by the humidity. Germination was not affected by the damage index, but it was affected by humidity and compression.La calidad física, fisiológica y sanitaria de la semilla se reduce debido al daño mecánico ocasionado por la mecanización del proceso de beneficio. Conocer los valores críticos de la fuerza y el desplazamiento a la compresión en función del tipo de endospermo, permitirá ayudar a disminuir el daño durante dicho proceso de limpieza, secado, almacenaje y manejo. En el presente estudio se evaluaron: la fuerza y el desplazamiento a compresión de ruptura, el daño visible y la calidad fisiológica de semillas de maíz de las variedades: Cacahuacintle (harinoso), HS-2 (semi-harinoso) y Palomero (duro) con humedad de 12 y 20%. El porcentaje de endospermo suave en Cacahuacintle, HS-2 y Palomero fue de 76.20, 33.43 y 15.27%, mientras que el de endospermo duro fue 5.25, 48.93 y 65.21%. El desplazamiento y la fuerza para Cacahuacintle, HS-2 y Palomero fue de 0.8264 mm y 274.71 N, 0.5499 mm y 309.07 N, y 0.5066 mm y 356.29 N; mientras que para 12 y 20% de humedad fue de 0.3279 mm y 312.52 N y 0.9520 mm y 313.81 N. Los índices de daño en semillas comprimidas fueron 276.67, 327.78 y 220.01 para Cacahuacintle, HS-2 y Palomero; mientras que para semillas sin comprimir (testigos) fue de 0.00. La germinación fue de 85.20 y 55% para semillas sin comprimir y para las sometidas a ruptura. El índice de daño estuvo afectado por la variedad y la compresión, pero no por la humedad. La germinación no estuvo afectada por el índice de daño, peri sí por la variedad, la humedad y la compresión