Influence of Heat Processing on Nutrient Composition and Energy Values of Selected Cereals Consumed in Nigeria

Aims: The influence of heat processing on the nutrient composition and energy values of selected cereals (Sorghum, Maize, Millet, and Rice) consumed in Nigeria were investigated.

Study Design: Cereals samples (100 g each) were weighed out for processing prior to analysis. The weighed samples were divided into two lots of raw and cooked sample. Raw sample was sun dried, further oven dried for 24 hours and ground into flour which passed through a 30-mesh test sieve. The second lot was cooked to tenderness by boiling with deionized water for 15 minutes at 120ºC. Thereafter, the cooking solution was discarded. Samples were drained, oven dried, ground using a food grinder (Model MX 491N, National) into flour 20-mesh screen and stored in a clean dry air-tight sample bottle in a refrigerator (4ºC) until required for analysis.

Place and Duration of Study: Analysis was done at the Department of Biochemistry, Anambra State University, between April 2014 and May 2014.

Methodology: Proximate composition was determined following standard methods. Mineral compositions were determined using Bulk Scientific Atomic Absorption/Emission Spectrophotometer 200A.

Results: Cooking significantly (P<0.05) increased the moisture content of the samples with maize retaining the highest moisture content. Dry matter, crude protein, crude fat, ash, total carbohydrate and calorific values decreased significantly after heat processing. Cooking also decreased the level of divalent metals Fe, Zn, and Ca, but increased the monovalent metal Na compared to their levels in raw samples except Cu that decreased significantly.

Conclusion: Heat processing significantly decreased the nutrient compositions of cereals.