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The study was accomplished to optimize the application of stress treatment to prevent chilling injury (CI) in tomatoes. Four treatments were evaluated: control, heat shock applied for 24 (HS24) and 48 h (HS48), and cold shock applied for 24 h (CS24). The fruits were stored at 2 and 14C, and evaluated immediately after treatment and after 21 and 28 days of storage. An additional evaluation after 7 days of exposure at 20C following storage withdrawal was included to induce ripening and exteriorize the development of CI symptoms. Different biochemical and quality attributes were evaluated (color, titratable acidity, firmness, ethylene, CI index and heat shock protein [HSP] accumulation). Heat treatments were successful in preventing the decay of fruits under CI-inducing conditions. The significantly better performance of HS48 in comparison to the other treatments gives evidence that the effectiveness relies on the adequate intensity of application; therefore, this intensity should be strictly controlled by a proper monitoring method. In this regard, small HSP accumulation was found suitable to reflect properly the physiological condition of fruits and therefore to potentially optimize and determine the adequate intensity of treatment application. PRACTICAL APPLICATIONSStress treatments constitute a promising technological alternative to extend the shelf life of fruits and vegetables because of their capacity to prevent the development of chilling injury during the cold storage of sensitive species. The main advantages are the ease of use, considering that they can be applied in commercial chambers with minor changes, and the avoidance of chemicals. By assessing the effectiveness of treatments and the suitability of different biochemical and quality attributes as monitoring parameters to maximize the efficiency of application, it became apparent that the adequate intensity of application must be accurately established, since beyond a certain limit, the effect of the stress may induce irreversible alterations, provoking a permanent damage. The study provides evidence that small heat shock protein accumulation constitutes suitable monitoring parameters to objectively establish the optimal intensity, able to maintain the quality characteristics and extend the shell life of tomatoes during the cold storage. Journal of Food Quality

injection of 0.25 M calcium chloride solution in less tender muscles, such as Biceps femoris, from relatively old animals produced tenderness increase in a shorter aging time (2 days). Protein degradation obtained after submitting muscle samples to the combination of calcium treatment plus two days of aging, was comparable to the proteolysis observed after 7 days of aging (Light Microscopy, Transmission Electron Microscopy, Polyacrylamide Gel Electrophoresis). Consumers were not only able to detect the resulting tenderness increment but also preferred calcium treated samples. The practice of calcium treatment on this widely used muscle -which is less tender, or with tenderness inconsistencies-has a benefit for both the industry and consumers.

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ResumenEl objetivo de este trabajo fue evaluar el efecto térmico residual generado luego del uso en ciclos consecutivos del equipo de Alta Presión Hidrostática (APH) en tres posiciones internas (superior, central e inferior) mediante la cuantificación del contenido de sulfhidrilos libres [SH-L] de α-amilasa de Aspergillus oryzae expresado en μmol de SH/g de proteína. La potencial utilización de la cuantificación de [SH-L] de la enzima como indicador de tratamiento de APH permite medir en forma indirecta el efecto térmico durante el proceso. En el ensayo se utilizó un equipo de APH de 2L con alimentación inferior del fluido de presurización (agua:propilenglicol-70:30v/v). En cada ciclo, el fluido a temperatura ambiente fue comprimido hasta alcanzar la presión deseada (605 MPa), y el nivel de presión se mantuvo durante cinco minutos con posterior despresurización. El ciclo fue repetido tres veces en forma consecutiva. Se realizó un ANOVA (α=0,05) correspondiente a un diseño factorial de dos factores: posiciones y ciclos consecutivos, con tres niveles cada uno, y con cuatro repeticiones para el diseño completo. Se obtuvieron diferencias significativas en la interacción ciclo*posición (p valor=0,001) y el ciclo (p valor=0,021). Estos resultados evidencian el efecto del calor generado durante la compresión adiabática, afectando la historia térmica de la α-amilasa. Dada su sensibilidad, esta enzima podría ser considerada a futuro como un indicador de procesos de APH que permite evaluar la diferencia entre las muestras procesadas durante los ciclos, y que evidencia el perfil térmico generado dentro del equipo. Palabras clave: Altas Presiones, contenido de sulfhidrilos libres, amilasa. AbstractWe evaluated the residual thermal effect generated by the consecutive High Hydrostatic Pressure (HHP) cycles relative to the position (upper, central and lower) inside a high pressure vessel determining the free sulfhydryl groups [F-SH] from pressurized α-amylase Aspergillus oryzae expressed in μmol SH/g protein. This methodology could represent a potential indicator of HHP treatment, allowing to measure in an indirect way the thermal effect during the process. Assays were carried out using a 2L stabilized lab scale equipment, where pressurizing medium (water-propilenglycol:70-30%) was injected at room temperature from the bottom of the vessel. For each cycle, the fluid at room temperature was compressed until reaching the desired pressure (605 MPa), maintained for five minutes, followed by depressurization. The cycle was repeated three consecutive times. The free sulfhydryl content was assayed statistically using one-way ANOVA (α=0,05) for a factorial design of two factors: positions and consecutive cycles, with three levels, and four repetitions for the complete design. Significant differences were obtained in the interaction cycles*position (pvalue = 0,001) and cycles (pvalue = 0,021). These results demonstrate the effect of the heat generation during adiabatic compression, affecting the thermal history of the α-amylase. Due to...

Heat shock proteins (HSP) are synthesized in living tissues exposed to transient increase in temperature and play a central role in the protective response against heat and other stresses. In fruits, this response to heat treatment provides resistance to a physiological alteration known as chilling injury. Despite the physiological importance of this group of proteins, publications comparing different methodological alternatives for their analysis are rather scarce. In the present paper, we conducted a comparative study using different electrophoretic and immunological techniques to evaluate the HSP response in fruits. Proteins were extracted from tomato fruit exposed to an HSP-inducing temperature (38 °C) for different times (0, 3, 20, and 27 h). Different alternatives of analysis (SDS-PAGE, SDS-PAGE followed by IEF, Western blot, and dot blot) were performed, and their potential application discussed. The study was complemented with a practical application, in which tomatoes were subjected to heat and anaerobic treatments and then stored in a chill-inducing temperature. This application evidences the relevance of knowing the level of proteins attained by stress treatments which correlates with the acquired tolerance.

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