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Characterisation of polyphenols and fatty acids isolated from tomato peel waste

It is well known that industrial processing of fruits and vegetables generate every year a huge amount of wastes that represent a worldwide problem from both the environmental and the economic aspects. This material is disposed of as a solid waste or used as animal feed, but the abundance of various compounds in by-product fractions suggested the possibility of utilizing it as a cheap source of value added chemicals, such as polyphenols and fatty acids. Thus, a good material for its isolation is under-utilised tomato biomasses generated from canning industry. In that context, this work presents application of ultrasound-assisted extraction as not yet explored method for polyphenols isolation from tomato peel waste. Effect of ultrasound parameters (time, temperature, frequency, power, amplitude and tip probe), as well as type of tomato peel waste (with and without pectin incorporated in tomato cuticle) and solvent polarity (70 and 96 % ethanol, v/v) was evaluated with regard to total phenols, total flavonoids and phenolic compounds recovery. After isolation of polyphenols, the tomato peel residues were re-utilised for fatty acids extraction by mixture of chloroform and methanol (50:50, v/v). The evaluation of fatty acids was performed in two follow steps, i.e. quantification by GC/FID analysis and characterisation of extracts using FTIR and NMR spectroscopy. The results showed that all tomato peel samples contained caffeic acid (43.5 to 106.6 mg kg-1of dried tomato peel), chlorogenic acid derivative (17.1 to 178.9 mg kg-1 of dried tomato peel), p-coumaric acid (2.1 to 7.0 mg kg-1 of dried tomato peel) and quercetin derivative (6.1 to 15.6 mg kg-1 of dried tomato peel). Regarding fatty acids, the saturated was isolated in greatest amount, i.e. 7.36 - 89.53 %, followed by polyunsaturated (8.46 - 18.97 %) and monounsaturated (3.36 - 10.31 %). The results of FTIR and NMR analyses confirmed triacylglycerol structure, bearing saturated and unsaturated. Considering a growing interest of consumers to intake natural compounds, it can be concluded that tomato peel waste presents one of promising resource for simultaneous recovery of value added compounds such as polyphenols and fatty acids.

Tomato peel waste ; Polyphenols ; Fatty acids ; FTIR and NMR spectroscopy

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