Pre-processing waste tomatoes into separated streams with the intention of recovering protein: towards an integrated fruit and vegetable biorefinery approach to waste minimization

A large proportion of the European Union’s tomato crop is discarded during harvesting and downstream processing and there is considerable potential for value addition to the various residue streams produced, using a cascade biorefinery approach. Cherry tomatoes were segregated into three separate components in order of proportion of dry composition: juice, pomace (pulp and peel), and seeds. The protein content of the seeds was highest with 27.4% while the pulp and peel contained 7.6%. Carbohydrase mediated hydrolysis revealed a minor increase in protein recovery from seeds by 10% using Filta 02L (cellulase, xylananse and β-glucanase), while from pulp and peel was increased by 210% using Tail 157 (pectinase, hemicellulase). Sequential washing of milled tomato seeds followed by low-speed centrifugation facilitated collection of two separate fractions comprising of a crude protein and tomato seed hulls. The fibre content of the hull fraction showed a higher fibre content of 65% compared with 47% in the seeds. A significant proportion of the fibre in the hull fraction was composed lignin although the protein contents between both fractions was similar ranging from 27.4% to 29.9%. These results provide some indication about which types of carbohydrases are effective on each component of the cherry tomatoes in aiding the recovery of protein and carotenoids