Process and product design: Tools to optimise the lycopene bioaccessibility of tomato-based food products

Lately, lycopene has attracted positive attention originating from the studies which suggest a possible inverse correlation between the consumption of lycopene rich foods and the risk of chronic diseases. Tomatoes are the major dietary source for lycopene. Furthermore, they are one of the most grown crops for processing. Industrial processing of tomatoes into different end-products includes mechanical treatments, several thermal treatment steps, and potentially the addition of other ingredients which might induce either desirable or undesirable quality changes. In this context, the present work aimed at an increased understanding of the effect of mechanical processing, more specifically high pressure homogenisation, and thermal processing on lycopene degradation, isomerisation, and bioaccessibility (i.e. availability for absorption). In addition, the impact of the presence of lipids during processing was investigated. In plain tomato pulp, lycopene demonstrated a high stability against degradation and isomerisation. High pressure homogenisation (80-1300 bar) hardly affected the total lycopene retention and isomeric distribution. Moreover, lycopene loss during thermal processing only occurred at treatment temperatures above 120 °C. Thermally induced isomerisation was also limited, even during heating at 140 °C.The decrease in lycopene bioaccessibility caused by high pressure homogenisation was shown to be related to microstructural changes. More specifically, the tomato network strength was inversely related to the lycopene bioaccessibility. It was hypothesised that the fibre network induced by high pressure homogenisation physically entrapped lycopene. Thermal processing increased the bioaccessibility of lycopene in plain tomato pulp. However, the increase was only significant after intense thermal processing (30 min at 130 and 140 °C). The results obtained clearly indicated that in plain tomato pulp lycopene bioaccessibility could only be increased by intense thermal processing at industrial irrelevant conditions which also (negatively) affect other quality parameters.Lycopene degradation and isomerisation reactions during heating were accelerated in the presence of lipids. Lycopene degradation in olive oil, fish oil and in an olive oil/tomato emulsion could be described by single response modelling using a fractional conversion model while multi response modelling was applied to describe lycopene isomerisation. In all media, lycopene degradation ceased after prolonged heating and a temperature dependent equilibrium state was reached. Lycopene degradation and isomerisation kinetic parameters depended on the reaction medium.Adding 5% of lipids (coconut oil, palm oil, cocoa butter, olive oil, sunflower oil, or fish oil) to plain tomato pulp prior to in vitro digestion significantly increased the lycopene bioaccessibility. This increase was more pronounced after applying lipids containing mainly C18, C18:1, or C18:2 fatty acids compared to applying lipids mainly consisting of C12 and C16 fatty acids. The degree of unsaturation of the composing fatty acids was shown not to be a determining factor. Adding 0-10% of coconut oil, olive oil, or fish oil to tomato pulp demonstrated that not only the type of lipid but also the quantity influenced the lycopene bioaccessibility. Interestingly, the type of lipid leading to the highest lycopene bioaccessibility depended on the amount added.In general, processing tomato pulp in the presence of 5% of lipids caused similar changes in the lycopene bioaccessibility compared to processing plain tomato pulp. Intense thermal processing (20 min at 120 °C) was necessary to significantly improve the lycopene bioaccessibility while heating 20 min at90 °C was sufficient to increase the lycopene bioaccessibility when high pressure homogenisation was applied prior to the heating step.Pilot scale aseptic processing at industrial relevant conditions confirmed the results obtained under laboratory scale conditions. Moreover, the identified kinetic models proved to be applicable to predict lycopene losses and isomerisation. The present work indicates that the presence of lipids combined with processing conditions which remove structural barriers can improve lycopene bioaccessibility in tomato-based products, while lycopene degradation remains limited. Consequently, these intrinsic and extrinsic factors are the key factors to optimally benefit from the purported health effects of lycopene in tomato-based products.

Jaar van publicatie:2012

Toegankelijkheid:Closed