Abstract The effect of different drying treatments (natural, 50 and 70 °C) and crop management (without and with re-fertilization at pre-silking) on the endospermic hardness in four hybrids maize (AW 190, NK 940, Condor and Mill 522) was studied. Hardness was assessed by test weight (TW), percent floaters (PF) in NaNO3 and CCl4, and milling ratio (MR). The trial was based on a factorial design. Generally, high TW and MR values, and low PF values are associated with flintier maizes. It was observed that artificial drying (at 50 and 70 °C) decreased MR, increased PF, and did not produce major changes in TW, thus decreasing hardness. Cóndor (natural drying) and with re-fertilization (drying at 50 °C), Mill 522 (natural drying and at 50 °C) and in the control management (drying at 70 °C) hybrids achieved hardness values for 'Premium' quality. The techniques used allowed to classify the hybrids by their hardness and to evaluate the effect of the drying temperature on it.

Resumen Se evaluó el efecto de distintos tratamientos de secado (natural, 50 y 70 °C) y manejo agronómico (sin y con re-fertilización en pre-floración) sobre la dureza endospérmica en cuatro híbridos de maíz (AW 190, NK 940, Cóndor y Mill 522). La dureza se evaluó mediante peso hectolítrico (PH), test de flotación (TF) en NaNO3 y CCl4 y relación de molienda (RM). El ensayo se basó en un diseño factorial. Generalmente, altos valores de PH y RM y bajos de TF están asociados con maíces más duros. Se observó que el secado artificial (50 y 70 °C) disminuyó RM, aumentó TF y no produjo mayores cambios en PH, disminuyendo así la dureza. Los híbridos Cóndor (secado natural) y con re-fertilización (secado a 50 °C), Mill 522 (secado natural y a 50 °C) y en el manejo control (secado a 70 °C) lograron valores de dureza para calidad ‘Premium’. Las técnicas empleadas permitieron clasificar los híbridos por su dureza y evaluar el efecto de la temperatura de secado sobre la misma.

Abstract The objective of this work was to analyze and defined an appropriate heat treatment for the sterilization of a low-calorie grape jam (39.26 ± 0.63 °Brix; pH 3.63 ± 0.04) obtained using fruits reduced in carbohydrates by optimized pretreatment, and natural Stevia sweetener to replace sucrose. For this purpose, different types of information and tools were used. The physicochemical characteristics and proximal composition of the jam were determined. Information as to what microorganisms as common saprophyte fungi in grapes can develop in these products was gathered from the available literature. The thermophysical properties of the product were determined. Different combinations of recommended time and temperature combinations for heat treatments that inhibit microorganisms were analyzed. FEM numerical were developed to predict temperature profiles during heat treatment. Also, microbiological analysis of yeast and yeast screening and counting was performed. As a result of this study, two heat treatments were proposed to inhibit the fungus B. fulva and B. nivea (common in grapes). Two autoclave sterilization processes (121.1°C; 20-32 lb/in2) were defined by the time-temperature combinations, T1: 100°C-5 minutes; T2: 100°C-10 minutes, to apply and maintain the desired temperature of 100°C throughout the product for 1.3-27 seconds. Both treatments were considered suitable for sterilizing a 190 g jam container and were validated by microbiological analysis.