This report presents a comprehensive review of the effects of tea particle size (PS), dipping temperature, infusion time, dipping frequency, and effect of permeance on tea infusion focusing on zobo (Roselle – Hibiscus sabdariffa) tea. Tea production process follows a series of unit operations depending on the type of tea being produced. Various forms of tea are scented, white, oolong, green, and black teas. Generally, the basic unit operation involves include withering, maceration, fermentation, fixation, rolling or shaping, drying, and curing or aging of the tea leaves. Before drinking, the processed tea is prepared by infusing the tea leaves in hot or cold water with or without tea bags. For maximum extraction of bioactive compounds which are responsible for the high nutritive and functional properties of tea, it is important to understand tea infusion process and factors affecting the infusion kinetics (IK). PS and distribution of food powders, their measurements, and their instrumentations are displayed as well as the undesirable phenomena in food powders. Tea packages and tea bag selections, the effect of different factors in tea IK, novel technology for tea production, and future prospects of tea production are also discussed. This review aims at providing information for the understanding of tea PS and factors affecting tea IK thereby enhancing the understanding of different principles behind tea infusion; a perspective on zobo production.

The properties of kernels, grains and seeds are important in the development of equipment for transportation, handling and processing. Physical and mechanical properties of Gmelina arborea where experimentally determined. The moisture content of Gmelina arborea was determined as 41.30%wb. The major, minor and intermediate diameters were 18.16 ± 1.79 mm, 10.52 ± 0.93 mm and 9.40 ± 0.81 mm respectively. The geometric and arithmetic mean diameter were calculated as 12.12 ± 1.10 and 9.56 ± 0.90 mm respectively. The sphericity was 66.91%, aspect ratio, 58.19, bulk and true densities, 0.64 kg/m3 and 0.96 kg/m3 respectively. The porosity and mass of a 1000 seeds were 66.67% and 621.33g respectively. The coefficient of friction determined on four different surfaces were; on wood, 0.4 ± 0.7, on galvanized steel, 0.37 ± 0.6, on glass, 0.36 ± 0.4 and on aluminum, 0.34 ± 0.6. The angle of repose was 24.09o. The compressive test conducted on the three major axes; vertical, horizontal and transverse shows that the energy needed for cracking of the Gmelina arborea is least on the horizontal axis, 0.808 ± 0.19 kN, followed by the vertical axis, 1.496 ± 0.35 kN and then the transverse axis, 2.39 ± 0.20 kN, with corresponding stress as 1.52 ± 0.35, 2.90 ± 0.45 and 4.90 ± 0.44 MPa respectively.