Protein quality of foods made incorporating Cycas circinalis seed flour

Abstract

Among the cycad species Cycas circinalis and Cycas zeylanica are native to Sri Lanka. Foods such as pittu and roti made by incorporating Cycas circinalis seed flour are consumed by Sri Lankans living in areas where the plant grows. Although previously reported data indicate that the content of protein in C. circinalis seeds is comparable to that of wheat flour, no data is available on the quality of cycad seed proteins. The present study was aimed at evaluating the quality of proteins in C. circinalis seed flour, pittu and roti made by incorporating cycas seed flour. The moisture, insoluble (IDF) and soluble dietary fibres (SDF), crude protein and digestible carbohydrate contents were measured by AOAC official methods (1984), method of Asp et al, Lowry’s method/ Folin Ceocalteau method and Holm’s method respectively. Quality of proteins was estimated by AOAC Official method 960.48, using an animal bioassay. Digestible carbohydrate content was highest in soaked seed flour (50.0±2.03). Among the cycad foods, highest protein content (10.3±0.01) and total dietary fibre content (7.7) were in roti and this could be due to the addition of wheat flour to roti instead of rice flour in pittu. Highest weight gain was observed in reference group fed with casein containing diet. The significantly high weight gain in the seed flour fed group compared to roti and pittu fed groups may be due to the high feed intake. No significant weight gain difference was observed between roti and pittu fed groups. Protein quality of C. circinalis seeds was comparable with that of common maize but all protein quality parameters [Protein Efficiency Ratio (PER), Food Efficiency Ratio (FER), Net Protein Retention (NPR) and Protein Retention Efficiency (PRE)] were significantly low compared to the reference protein diet. Although not significant, NPR and PRE values in roti (1.4±0.6 and 8.5±3.7) were higher than test food made with pittu or raw seed flour.