Toxin removal during protein extraction from tomato leaves

Abstract

Protein production from agricultural side streams aids in global crop valorisation. This study aimed to isolate protein from tomato leaves (Solanum lycopersicum) with simultaneous toxin removal for use as a food ingredient. Protein was isolated through three methods; pH precipitation, ethanol precipitation, and a combination of heat coagulation and filtration. Protein yield and purity were determined and protein isolates were tested for presence of the toxins, tomatine and dehydrotomatine. Protein recovery was 6–10% of the original total protein content. The pH precipitation method yielded a powder with the highest purity of 76%, but was least effective at removing toxins. Ethanol precipitation removed toxins most effectively, but gave a low protein purity of 40%. The combination of heat coagulation and filtration gave the optimal result, yielding a high purity protein powder of 71% with 99.7% of toxins removed. However, absolute toxin levels might still be too high and safety assessment of toxin removal will be necessary. Industrial relevanceLeaves can be a good source of protein and Rubisco product from sugar beet leaves is now undergoing EFSA approval. Water lentil (Lemna) protein concentrate has recently been approved. The generally low yield of protein product from 1 kg of (wet) leaves is most challenging in these processes compared to more efficiently obtained isolates from (dry) pulses. The better functionality of Rubisco should compensate for that. Rubisco protein from tomato leaves (Solanum lycopersicum) can also be recovered, although toxins need to be removed to allow for human consumption. This additional hurdle will make industrial implementation more difficult.