Valorisation of Tomato Peel Waste as a Sustainable Source for Pectin, Polyphenols and Fatty Acids Recovery Using Sequential Extraction

Abstract

The opportunity of tomato peel waste exploitation for simultaneous recoveries of high value compounds, such as pectin, polyphenols and fatty acids (FAs) is presented in this work. Prior to polyphenols and FAs extraction, the pectin removed from tomato cuticle was evaluated as possible tin corrosion inhibitor using electrochemical impedance spectroscopy. Subsequently, de-pectinized tomato peels are evaluated as appropriate bio-substrate for polyphenols and FAs recovery, using chromatographic analyses. Corrosion tests (24 h) showed that pectin (4 g/L) isolated from tomato peel act as more efficient tin corrosion inhibitor (η = 65.8%) than commercial apple pectin (η = 52.3%), which points out that it could be used as natural corrosion inhibitor. The polyphenols data showed that de-pectinized samples contained higher amounts of total phenols (2485.68–4064.46 mg/100 g, in 96% ethanol) and chlorogenic acid derivative (86.13–454.34 109 mg/100 g, in 70% ethanol) than samples with pectin incorporated in tomato cuticle. In addition, de-pectinized samples contained more polyunsaturated FAs (~ 45%) than samples with pectin (~ 26). Furthermore, both types of peels contained linoleic, palmitic and oleic acids as three dominants, and thus represented valuable source of nutritive oils. Their presence was also confirmed by FTIR and NMR spectroscopy. Therefore, obtained findings revealed that already exploited tomato peel for pectin production could be effectively re-used for polyphenols and FAs recoveries, providing valuable benefits, either for producers and consumers, such as decreasing the waste disposal costs and take opportunity that isolated compounds could be reintroduced into food.