Grape skin and seeds hardness assessment by texture analysis

Abstract

In order to optimize wine quality it is important to first characterize grape phenolic maturity and to determine the extractability of phenolic compounds during winemaking. The choice of harvest date is therefore very important but nevertheless still empirical. Previous works showed the interest of grape texture measurement as factor of grape maturity characterization. This work proposes to focus on berry skins and seed texture properties of three grapevine varieties: Cabernet sauvignon, Pinot noir and Nebbiolo from different growing areas and during two vintages, using a Universal Testing Machine TaxT2i Texture Analyzer. For the measurement of berry skin hardness, a needle probe was used, whereas for seed hardness a flat P/35 cylinder probe was used until a 50% deformation was reached. Tests were performed at 1mm.s -1 . Every test gave a force-deformation curve indicating the applied force at the skin and seed rupture point and the involved rupture energy. The first part of the study concerned the validation of the method used for grape skin and seed hardness measurements. The second part was dedicated to the importance of grape skin and seed hardness for the varietal differentiation The collected data showed that since there is a significant difference between varieties, berry skin and seed hardness represents a meaningful parameter for varietal characterization and differentiation. In both years 2004 and 2005, Nebbiolo was the variety with the toughest seeds (55,8N and 58,9N), but with the weakest berry skins (0,46N and 0,35N), in comparison to Pinot noir, which had the weakest seeds (35,9N and 41,3N) but the toughest berry skins (0,57N and 0,50N). Cabernet sauvignon showed a medium hardness for berry skins (0,51N and 0,46N) and seeds (44,5N and 43,4N).

Structure (micro, ultra, nano), color and mechanical properties of Vitis labrusca L. (grape berry) fruits treated by hydrogen peroxide, UV–C irradiation and ultrasound

“…The force was recorded every 0.33 s. Each specimen was placed on a flat steel holder (10 mm thick) with a hole (10 mm in diameter) in the center and was penetrated on the equatorial side (perpendicular to the abscission zone). This appears to be the best position for grape puncture test as supported by previous studies by Lee and Bourne (1980) and Letaief et al (2006). From the forcedisplacement curve, three mechanical parameters were computed.…”

“…The authors concluded that, after ripeness, skin strength and elasticity dropped severely, and the loss of cell wall polysaccharides was compensated by the inclusion of structural proteins. Letaief, Rolle, Zeppa, and Gerbi (2006) focused their interest on grape texture measurement as a grape maturity index, and reported not significant differences between berries picked from different bunch positions.…”

Sensibilidade ao rachamento de bagas das videiras 'Concord', 'Isabel' e 'BRS Rúbea'

“…Segundo Hankinson et al (1977), a resistência à compressão está ligada à coesividade entre as células da epiderme, enquanto a resistência à perfuração está relacionada ao tamanho destas células. Letaief et al (2006) obtiveram valores de força de perfuração para as cultivares Cabernet Sauvignon (0,46 N),Pinot Noir (0,50 N) e Nebbiolo (0,35 N). Fava et al (2011) encontraram valores de 4,9 N para força máxima de perfuração da cultivar Isabel, superior ao obtido no presente trabalho, porém utilizaram uma sonda de três milímetros de diâmetro com ponta de seção plana e não do tipo agulha, o que pode ter provocado um efeito parcial de compressão.…”

“…Yamamoto e Satoh (1994) adaptaram para videira um método descrito por Verner e Blodgett (1936) para cerejas, determinando o índice de rachamento por imersão das bagas de uva em água destilada. Outros autores avaliaram a relação do rachamento com aspectos histológicos (HANKIN-SON et al, 1977), estruturais (CONSIDINE, 1981(CONSIDINE, e 1982MATTHEWS et al, 1987) e mecânicos (CON-SIDINE; KRIEDEMANN, 1972;LETAIEF et al, 2006). Existem poucos trabalhos de determinação da sensibilidade ao rachamento das principais cultivares de uva para processamento produzidas no Brasil (YAMAMOTO; SATOH, 1994;FAVA et al, 2011).…”

Evaluation of grape and wine quality parameters of Agiorgitiko (Vitis vinifera K. cv.) cultivar qrown in Nemea

“…However, during sensory evaluation seed bitterness may be overwhelming and though distinguishing levels of bitterness / harshness may not be possible. Similarly, seed crushability (hardness) even though is a good indicator of grape maturity (Letaief et al, 2006) it is difficult to define obvious differences especially in the latter stages of fruit ripening.…”