Vegetable trimming waste is an interesting source of protein that is currently not being utilised. Wageningen Food & Biobased Research, Dutch company Provalor and research organisation TNO are carrying out research into the value creation of trimmings from endive, spinach and lettuce. The protein in these trimmings is an interesting addition to protein sources, which are in high demand due to the fast-growing global population.
“We process vegetable residue streams into high-quality ingredients,” says Paulus Kosters, director of Provalor. “The ‘waste’ from vegetable trimming companies – which trim lettuce & endive and package it in units – consists of the outer leaves and heads. For us this trimming waste may be a good source of protein. Having a constant availability is important for establishing a business case. In addition, our company has a wealth of experience in the processing of vegetable waste streams so it’s not necessary to establish a new logistic chain.”
From grinding to upgrading
Provalor uses the technological expertise of TNO and Wageningen Food & Biobased Research to unlock and upgrade the released protein as efficiently as possible. “The process of protein extraction from the trimming waste is complex,” explains Wim Mulder, senior researcher at Wageningen Food & Biobased Research. “First we unlock the protein by grinding the vegetable trimmings. Heating then causes the green cell membrane fragments to coagulate, which enables separation by means of centrifugation. The protein – RuBisCO – which remains in the liquid stage must then be purified further to make it suitable for food products.” According to Mulder, the technological challenges are mainly in the downstream processing: the purification and upgrading of the protein.
Opportunities for application as protein gel
The application opportunities of the protein from trimming waste depend, among others things, on functional properties such as emulsifiability, foam formation or the capacity to make a gel. The released protein especially enables the latter application: it forms a gel at lower concentrations than egg-white and whey proteins. “This makes it possible to market the protein as a full-quality vegetable alternative,” says Paulus Kosters. Further research will need to provide insight into the nutritional value, digestibility and further functionality of the protein. Applications in food require approval under the novel EU food regulations.
Kosters expects that the first pilot plant in which vegetable trimming waste is processed this way will be operational in 2018 and is positive about the outcome: “This project is well-aligned to our processes. We use agricultural waste streams by isolating and unlocking valuable and functional ingredients – in this case protein. We will further develop the concept within the European GreenProtein project, and expect to realise an industrial application within the next five years.”