Variability in the composition of potato protein concentrate produced in different starch factories—A preliminary survey

Eighteen samples of potato protein concentrate (PPC) produced in 3 starch factories (A, B and C) during 6, 4 and 8 consecutive 10-day periods were analysed for dry matter (DM), crude protein, ash, starch, available lysine, total solanidine glycoalkaloids contents and trypsin inhibitor activity. In addition, 3 pooled samples, representative of the PPC produced in each of the 3 factories during the whole campaign, were analysed for crude fibre, fat and amino acid content. Significant differences were found among factories for crude protein (800.3 and 807.0 g/kg vs 824.0 g/kg DM, P≤0.001), starch (72.8 and 74.7 g/kg vs 76.8 g/kg DM, P≤0.01), and ash (26.4 and 28.1 g/kg vs 30.6 g/kg DM, P≤0.001) contents. The amino acid content of the pooled PPC samples was similar for the 3 plants, with an average value of 7.63 for lysine, 3.67 for methionine and cystine, 5.43 for threonine and 1.44 g/16 gN for tryptophan. Solanidine glycoalkaloids concentration was lower in PPC from A and B than C factory (1390 and 927 mg/kg vs 2632 mg/kg, P≤0.001, respectively). Also, trypsin inhibitor activity differed among plants (0.97, 3.70 and 2.28 mg/g, for factories A, B and C, respectively, P≤0.001). The composition of PPC did not change during the campaign. It is concluded that the chemical composition of PPC is fairly uniform whereas the concentration of antinutrients differs considerably among plants.