QUALITY OF TOMATO FERTI LIZED WITH NITROGEN
The influence of different levels of nitrogen (N1, N2), phosphorous (P1, P2) and N+P (N1P1, N1P2, N2P1, N2P2) mixed fertilizers was investigated on volatile substances, soluble sugars, organic acids, titratable acidity, dry matter and lycopene of “Corbarino” cherry-like tomatoes. The flavor volatiles reached the highest concentrations in red-ripe cherry-like tomatoes treated with N1. Glucose, fructose, dry matter and titratable acidity increased only in N+P fertilized samples. Among the organic acids, citric increased, malic decreased and oxalic was constant in all the fertilized samples. Lycopene reached the highest ...view middle of the document...
] (DI CESARE et al. 2003).
Hexanal, 2(E)-hexenal, 3(Z)-hexen-1-ol, 2-isobutylthiazole, are considered to be responsible for the fresh tomato flavour (DIRINCK et al. 1976). While, according to other authors (BUTTERY et al. 1989; BUTT ERY, 1993; BUTT ERY and LING, 1993 a,b) 3(Z)-hexenal, β-ionone, hexanal, β-damescenone, 2(E)-hexenal, 1-penten-3-one, 2 and 3-methylbutanols, 2-isobutylthiazole, 2-isobutylcyanide, 2(E)-heptenal, phenylacetaldehyde, 6-methyl-5-hepten-2-one, 3(Z)-hexenol, 2 phenylethanol, methylsalycilate are considered to be important contributors to tomato flavour.
Soluble sugars and organic acids play an important role in the characterization of the tomato taste. Sugars (glucose, fructose and traces of sucrose) and organic acids (citric, malic and oxalic) represent half of the total dry matter of tomato fruit (SILVESTRI and SIVIERO, 1991).
In tomato cultivation, fertilizer application regimes can play an important role both to increase the yield and size and to improve the nutritional and nutraceutical quality of the fruit. A large amount of N is required for optimum production as the tomato root absorbs a great deal from the soil. N-deficiency can cause a decrease in production (number and size of tomatoes), a reduction in storage quality, colour, and
tomato taste (SAINJU et al., 2003).
Secondary plant metabolites which lack N in their structure such as lycopene, β-carotene, phenolics and flavonols are favoured under Nlimiting conditions, although photosynthetic activity is not simultaneously reduced. However nitrogen-containing compounds are favoured when N is readily available and not limiting to growth (DORAIS et al., 2008).
As far as nutritional quality and suitability for processing are concerned, many authors have highlighted the negative effects of excessive N, such as an increase in pH and a decrease in soluble sugars, soluble solids, dry matter, sugars/dry matter ratio and firmness (Kaniszewski et al., 1987; KOONER and RANDHAWA, 1990;PARISI et al., 2006).
XU et al. (2001) found that by using an application of nitrogen within the proper range increased the concentration of the volatile compounds in tomato, while an excessive N application decreased their concentration.
YU-TAO et al. (2007) studied the effects of applications of N levels on volatile substances, taste
compounds and firmness of fresh tomato fruits. The results pointed out that increasing N application increased the concentrations of 1-penten- 3-one, hexanal, 3(Z)-hexenal, 2-methyl-4-pentenal, 2(E)-hexenal, 6-methyl-5-hepten-2-one, titratable acidity, soluble sugars and soluble solids; under the same conditions the concentrations of phenylacetaldehyde decreased, whereas the concentration of 2(E)4(E)-hexadienal and firmness of fresh tomato fruit initially increased and then decreased.
WRIGHT and HARRIS (1985) pointed out that flavour scores indicated that increasing N and K fertilization had a detrimental effect on tomato flavour. An increase in...