Open access publications in the SLU publication database

Abstract

Protein-based plastics are considered as a new route for valorisation of oilseed meal from the industrial oil crops Crambe abyssinia (crambe) and Brassica carinata (carinata) as they cannot be used for animal feed or human food. To convert oilseed meals into protein-based plastic films compression moulding was used with varying processing temperature, chemical additives and protein extraction conditions. Twin screw extrusion was utilized to make films from blends of crambe meal and wheat gluten with urea as a combination denaturant and plasticizer. Tensile properties were examined and related to protein solubility and protein molecular weight (MW) distribution to reveal the underlying effects of different processing conditions.

Varying the plasticizer content (glycerol) in crambe and carinata meal based plastics resulted in a variety of tensile responses with protein MW distributions (HPLC) indicating that the tensile changes were due to plasticization effects. Forming oilseed meal films at temperatures between 100 and 180 °C indicated a minimum in solubility between 130 and 140 °C, corresponding to the highest Young’s modulus and maximum stress. From a range of additives to crambe and carinata meal films, NaOH and NH₄OH had the most positive effect on strain at maximum stress, especially at the lowest dose of NaOH (1.4%) which also resulted in the lowest protein solubility. Processing crambe meal/WG/glycerol/urea blends with co-rotating twin screw extrusion produced continuous protein-based plastic films within a limited temperature and composition window. Proteins were extracted from crambe meal under a variety of conditions with concentrates from alkali extraction/isoelectric precipitation showing the lowest protein solubility after heating. The relationship between processing, MW distribution and film properties is complex. Maximum protein aggregation resulted in improved properties in some cases, while in others the properties are controlled by mechanisms other than protein aggregation.