Effects Of Nitrogen, Phosphorus And Potassium Application On Flavor Compounds Of Fresh Tomato Fruits

Tomato is among the ten most important fruits and vegetables in consumption in the world, and its characteristic sour-sweet flavor is preferred. However, more popular complaints are being expressed of the poor flavor quality of fresh tomatoes available in consumer markets. Although fertilization has been regarded as one of the most important quality influencing factors of tomato, its possible effects on the flavor compounds of fresh tomato fruits, especially the volatile compounds, taste compounds and texture of fresh tomato fruits have rarely reported. Effects of nitrogen, phosphorus and potassium application on tomato flavor compounds and the relationship between volatile compounds, taste compounds and texture of fresh tomato fruits were studied using pot culture with sand, which would provide a plant nutrition science based information for rational fertilization for preferred flavor and high yield tomato production. The main results of the thesis are summarized as follows:1. Effects of nitrogen, phosphorus and potassium application on yield of fresh tomato fruitsSignificant differences in yields of fresh tomato fruits at different levels of nitrogen, phosphorus and potassium application levels were observed. The yields of fresh tomato fruits tended to increase first and decrease after the highest yield within the range of tested levels of N, P and K application. The optimal level of N, P and K application based on yield ranged from 4.50 mmol/L to 9.00 mmol/L, from 0.50 mmol/L to 1.00 mmol/L, and from 1.25 mmol/L to 5.00 mmol/L, respectively. Significant interactive effects of N and K on yield of fresh tomato fruits were observed, and the highest yield was found in the treatment with combined application at N 9.00 mmol/L and K 5.00 mmol/L.2. Effects of nitrogen levels on flavor compounds of fresh tomato fruitsWhen N fertilizer was applied at the levels from 2.25 up to 36.00 mmol/L, the contents of 6 volatile compounds (1-penten-3-one, hexanal, cis-3-Hexenal, 2-methyl-4-pentenal, ,trans-2-Hexenal, and 6-methyl-5-Hepten-2-one) and 3 taste compounds (titratable acidity, soluble sugar and soluble solids) increased with increasing rates of nitrogen application. The contents of 3-methyl-butanal and 2E-4E-hexadienal, and firmness of fresh tomato fruits increased first and then decreased with increasing rates of N application. The contents of phenylacetaldehyde, phenol and phenylethanol decreased with increasing rates of N application. Non-significant differences were found in Hexanoic acid content, SE/TA (the ratio of soluble sugar to titratable acidity) and SS/TA (the ratio of soluble solid to titratable acidity) with different rates of N application.The relationship between nitrogen (N) levels and 13 flavor compounds (hexanal, cis-3-Hexenal, 2-methyl-4-pentenal, trans-2-Hexenal, 6-methyl-5-Hepten-2-one, phenylethanol, titratable acidity soluble sugar, and soluble solids) and firmness of fresh tomato fruits could be well described by linear or curvilinear equation.3. Effects of phosphorus levels on flavor compounds of fresh tomato fruitsWith the rates of P application ranged from 0.00 mmol/L to 4.00 mmol/L, the contents of 4 volatile compounds (l-penten-3-one, hexanal, cis-3-Hexenal and trans-2-Hexenal) increased first and then decreased, and the relations of P levels to other volatile compounds and taste compounds could not be well observed. The firmness of fresh tomato fruits tended to increase with increasing rates of P application.The relations of P level to 4 flavor compounds (l-penten-3-one, 3-methyl-Butanal, Hexanal, and soluble solid), the ratio of soluble solid to titratable acidity and firmness of fresh tomato fruits could be well described by curvilinear or linear equation.4. Effects of potassium levels on flavor compounds of fresh tomato fruitsWhen K fertilizer was applied at the rates of 0.00-20.00 mmol/L, the content of 5 volatile compounds (3-methyl-Butanal, hexanoic acid, phenylacetaldehyde, phenol and phenylethanol) tended to increase and then to decrease with increasing rates of K application. When the rates of K application ranged from 0.00 mmol/L to 10.00 mmol/L, the content of 7 volatile compounds (l-penten-3-one, hexanal, cis-3-Hexenal, 2-methyl-4-pentenal, trans-2-Hexenal, 2E-4E-hexadienal and 6-methyl-5-Hepten-2-one) and taste compounds (soluble sugar and soluble solids) increased first and then decreased with increasing rates of K application, whereas significant increases in content of these flavor compounds at the rate of K 20.00 mmol/L were found comparing with K application at 10.00 mmol/L. In general, the content of titratable acidity and firmness of the fresh tomato fruits tended to increase with increasing rates of K application, whereas the ratio of soluble sugar to titratable acidity and the ratio of soluble solid to titratable acidity tended to decrease with increasing rates of K application.The relations of K levels to titratable acidity and firmness of fresh tomato fruits could be well described by linear equations. The relations of K levels to contents of 8 volatile compounds (3-methyl-Butanal, l-penten-3-one, hexanal, cis-3-Hexenal, 6-methyl-5-Hepten-2-one, hexanoic acid, phenylacetaldehyde, and phenylethanol), taste compounds (soluble sugar and soluble solid), and the ratio of soluble sugar to titratable acidity and soluble solid titratable acidity could be well described by curvilinear equations.S. Interactive Effects of nitrogen and potassium on taste compounds and firmness of fresh tomato fruitsSignificant interactive effects of N and K on taste compounds were observed. The highest contents of titratable acidity, soluble sugar and soluble solid were found in the treatment with combined application of N 18.00 mmol/L and K 10.00 mmol/L. The highest ratio of soluble sugar to titratable acidity and soluble solid to titratable acidity was found at a combined application of N 4.50 mmol/L and K 0.00 mmol/L. Obvious interaction of combined application of N and K on content of titratable acidity,and the ratio of soluble sugar to titratable acidity and soluble solid to titratable acidity was observed.6. Relationship between flavor compounds of fresh tomato fruits under different levels of nitrogen, phosphorus and potassium applicationClose relationships between flavor compounds under different rates of N, P and K application were found. The content of each of 7 volatile compounds (3-methyl-Butanal, l-penten-3-one, hexanal, cis-3-Hexenal, trans-2-Hexenal, 6-methyl-5-Hepten-2-one and phenylacetaldehyde) was significantly correlated with more than 6 other volatile compounds, respectively. The content of titratable acidity was significantly correlated with content of soluble sugar and soluble solids, and the ratio of soluble sugar to titratable acidity and the ratio of soluble solid to titratable acidity. Content of taste compounds was closely correlated with content of volatile compounds, and the content of titratable acidity, soluble sugar and soluble solid was significantly correlated with the content of more than 8 volatile compounds, respectively. Firmness of fresh tomato fruits was significantly correlated with content of 2E-4E-hexadienal.To some extent, there was a definite relationship between flavor compounds of fresh tomato fruits under different levels of P application. The content of hexanal, phenylethanol, trans-2-Henenal, 2E-4E-hexadienal, l-penten-3-one and hexanoic acid was significantly correlated with the content of more than 5 volatile compounds. There was also a definite relationship between taste compounds. Content of soluble solid was significantly correlated with the content of l-penten-3-one and hexanoic acid. Firmness of fresh tomato fruits was significantly correlated with the content of volatile compounds, but negatively correlated with the ratio of soluble sugar to titratable acidity.Obvious relationship between the content of flavor compounds of fresh tomato fruits under different levels of K application was observed. The content of each of 8 volatile compounds (l-penten-3-one, hexanal, 2-methyl-4-pentenal, trans-2-Hexenal, phenylacetaldehyde, hexanoic acid, phenol and Phenylethanol) was significantly correlated with the content of more than 6 volatile compounds, respectively. Notable relationships between taste compounds were found. To some extent, the content of volatile compounds was correlated with the content of taste compounds. Firmness of fresh tomato fruits was insignificantly correlated with the content of volatile compounds and taste compounds, respectively.