Evaluation of quality characteristics of three different colour tomato varieties in three ripening stages

Abstract

Fruit ripening and softening indicated by firmness determines the texture transportability, and shelf life of tomato products. However, the regulatory mechanism underlying firmness formation in tomato is different in different varieties and overall softening mechanism of tomato fruit is poorly understood. Therefore, in this study, physical, biochemical, and molecular properties of three different tomato varieties; ‘Sarikiz’ (yellow skin colour), ‘Moda’ (orange skin colour) and ‘Red Type Cherry’ (red skin colour) at three developmental stages, mature green (MG), breaker (Br) and full ripe (R) were evaluated. For this aim, colour, texture, cell wall fractionation and pectate lyase (PL) gene expressions were analysed at three different ripening stages. As expected, there was a dramatic difference in colour index due to different skin colours of the varieties. For textural properties, ‘Sarikiz’ showed the softest while ‘Moda’ variety had the firmest pericarp structure. The composition of the cell wall structure at three ripening stages were also resulted with significantly different fractions. The expression of pectate lyase (PL), one of the most important cell wall modification related enzyme was also studied by semi quantitative RT-PCR. Based on biochemical and molecular studies, ‘Sarikiz’ showed higher pectin fraction in water and PL gene expression at Br and R ripening stages. Based on these results, although the tomato fruits used in this study generally show the same softening trend, they show different physiological, biochemical, and molecular changes in different softening periods.