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Study of two methods used to quantify the berry firmness of Thompson seedless grapes.

2001; Pontifical Catholic University of Chile; Volume: 28; Issue: 1 Linguagem: Inglês

10.7764/rcia.v28i1.433

0718-3267

A. Vargas, J. Pérez, Juan Pablo Zóffoli, A. Pérez,

Fermentation and Sensory Analysis

In order to develop a tool to quantify the berry firmness of export table grapes for long distance markets, two different methods were compared using soft and firm berries. The first method was the measurement of skin punctured strength with a Texturometer (TA-XT2). From the force-deformation curve, six variables were established: “Force at the skin rupture point”, “Gradient or elasticity coefficient”, “Area under the curve”, “Curvature degree”, “Percentage of Deformation and “Final Force”. The second method was described by the Department of Viticulture and Oenology of the University of Stellenbosch in South Africa, (1996). Through this method it is posible to obtain the firmness of intact berries, the firmness of the berry flesh and, by subtraction, the firmness of the berry skin and the force due to the turgor applied to the berry skin in the intact berry. High correlation coefficients were observed between the firmness of the intact berry and the firmness of flesh berry (r=0.93), the firmness of intact berry and Gradient or elasticity coefficient (r=0.90), the firmness of the flesh berry and Gradient (r=0.80) and the firmness of berry skin and Gradient (r=0.78). It was concluded that the elasticity coefficient can be considered as a good berry flesh firmness index.Con el proposito de desarrollar una herramienta que permita cuantificar la firmeza de las bayas de uva, durante la temporada 1999 se cosecharon 120 racimos de la variedad Thompson seedless desde tres localidades de la zona central de Chile: Llay-Llay, San Francisco de Mostazal y Naicura. Sesenta racimos considerados con bayas firmes y sesenta con bayas debiles, para obtener una mayor variabilidad en la firmeza de la fruta. Se muestrearon seis bayas por racimo para medirles su textura; tres bayas fueron medidas a traves del metodo de analisis de la curva fuerza-deformacion desde donde se obtuvieron seis variables de textura: Pendiente, Fuerza Maxima, Area bajo la curva, grado de Curvatura, Deformacion y Fuerza Final; y tres bayas medidas segun el metodo descrito por la Universidad de Stellenbosch. Segun este metodo se pudo medir en la misma baya la contribucion a la firmeza de la pulpa, de la pelicula y del turgor de la baya. Se obtuvo altos coeficientes de correlacion entre la pendiente al punto de ruptura y la firmeza total de la baya intacta (r=0,90), entre la firmeza de la pulpa y la pendiente (r=0,80), y entre la firmeza de la pelicula y la pendiente (r=0,78). Por lo tanto la variable de textura pendiente al punto de ruptura se considero un indice de la consistencia de la pulpa y de la crocancia de la baya.