Protein conversion efficiencies of four test diets based on milk, two milk and tea treatments, and casein

Milk consumption in 80 households in western Kenya averaged .25 to 1.00 L per family per day. Most of this milk was processed into a milk and tea beverage. Polyphenols, the major determinants of tea flavor and character, form soluble complexes with casein when black tea infusions are mixed with milk. Test diets were prepared from the following treatments: a) casein reference diet; b) milk, no tea leaves; c) milk added after heat treatment; and d) traditional Kenyan-style tea (i.e., milk and tea leaves heated together). Four groups of 10 male 21-day-old Sprague Dawley weanling rats were assembled and assigned to the test diets. Weight gain and protein intake (g/g) during a 28-d test period for the four diets were 1.94, 2.99, 2.93, and 2.77. The least significant difference test showed weight gain for protein intake was greater for rats on the milk-based diet and the diet with milk added after heating than for rats on the traditionally prepared milk and tea drink. Rats did most poorly when assigned to the casein reference diet. Modification of traditional Kenyan tea preparation practices (i.e., adding milk after tea leaves have been removed) might improve the nutritional value of the most popular milk product in western Kenya.