Physico-chemical and nutritional properties of meat analogues based on Spirulina/lupin protein mixtures

The effect of the addition of Spirulina platensis flour and of extrusion parameters on texture, cooking yield, expressible moisture, total phenolic content (TPC), total flavonoid content (TFC), Trolox equivalent antioxidant activity (TEAC), in vitro protein digestibility (IVPD) and conformational changes of proteins using Fourier-transform infrared spectroscopy (FTIR) of lupin protein based meat analogues was studied. High moisture extrusion (HME) cooking was used to produce the meat analogues. The Spirulina concentration (15, 30 and 50%), extruder barrel temperature (145 degrees C, 160 degrees C and 170 degrees C), water feed (50, 55 and 60%), and screw speed (500, 800 and 1200 rpm) were varied. The Spirulina concentration and extrusion parameters significantly affected physical properties, such as texture, cooking yield and expressible moisture of the extrudates. The addition of Spirulina generally increased the TPC, TFC and TEAC values of the extrudates. Increased temperature and screw speed as well as decreased water feed slightly improved the content of TPC, TFC and TEAC, respectively. The addition of Spirulina at a level of 30% decreased the IVPD of the extrudates from 82 to 75.6%. However, increased water feed and screw speed partly counterbalanced this effect. Protein conformational analyses of the extrudates by FTIR showed that beta-sheets were decreased, whereas alpha-helix, beta-turn and antiparallel beta-sheets were increased compared to the raw extrusion mixtures. On the whole, the HME process improved the values of TPC, TFC, TEAC and IVPD in the extrudates compared to the raw extrusion mixtures. The addition of Spirulina along with controlled extrusion parameters can deliver meat analogues with improved physico-chemical and nutritional properties.