Effects of brine strength and anoxia of fermentative enzyme expression and activity and quality characteristics of "Ailsa Creg" tomatoes
2006
Frangkostefanakis, S.
The fermentation process of mature green tomato fruits (Lycopersicon esculentum var. Ailsa Craig) was studied through exposure to anoxic conditions (100% N2) and under different salt concentrations (0%, 5% 10% NaCl). Changes in quality characteristics of fruits (firmness, pH, TSS, TA), expression and enzymatic activity of fermentation genes (Adh, Pdc, Ldh) and the activity of the respective enzymes were studied, for 0.5, 1, 1 2, 3, 7, and 14 days. Simultaneously, samples of brines were collected for further analysis. Discrepancies in responses that result from the different salt concentrations were obtained at molecular and quality levels. The complex kinetics of solutes between the fruits and the surrounding solution lead to different -espouses of the tissue to fermentation. Fruits held in H20 without salt had higher titratable activity, lower TSS, and higher expression or activity of the fermentation enzymes. Fruit held in 10% NaCl appeared to he less fermented while those held in 5% NaCl treatment showed signs of absence of fermentation and improved tolerance stress; Expression of the genes was detected on the 7th day of the experiment. However, 10% of NaCl-DEPC-treated fruit had a more steady and smoother response to stress. Additionaly, this treatment resulted in better quality even after 30 days of treatment. Unwashed fruits had a more steady response in gene expression, enzyme activity, and quality than the fruits of the other treatments. Anoxia-treated tomatoes, despite the higher LDH activity and pdc expression than the H20 treated ones showed insignificant fermentation. This inability of the tissue to be self fermented has led to fruits deterioration.
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