Tropical milk production systems and milk quality: a review.

We reviewed information on dairy cattle production systems in the tropics, the factors involved, and their influence on milk composition. Genetic factors had greater influence on milk production; specialized breeds produced more milk, and there was an inverse relation between the content of fat, protein, total solids, and the amount of milk produced. Season was related to the availability of forage, and the type of grazing system. Greater pasture area increased individual production, while a greater supply of feed concentrate did not increase milk production. The number of calvings positively affected milk production through the fifth calving, with subsequent declines in production. Milk production increased to a maximum and then declined as lactation progressed. Specialized systems had higher production and better hygienic milk quality; milking and container equipment are critical for maintaining milk sanitary quality. Factor interaction is highly complex, preventing the generation of specific recommendations and general principles applicable to the specific conditions for each system.

Influence of pretreatments on oil absorption of plantain and cassava chips.

The objective was to evaluate the effect of pretreatments of CaCl2 and osmotic dehydration (OD) on oil absorption in plantain and cassava chips. Plantain and cassava slices (1 mm thickness and 35 mm diameter) were prepared. Pretreatment with and without 5% CaCl2 solution before applying OD with sucrose solutions at 30 and 45%, and NaCl at 3 and 6% in a product/solution ratio of 1:25, at 40 °C were employed. OD kinetics and diffusivity were estimated by Page's model and Fick's law, respectively. Best OD treatments for plantain chips were 45% sucrose with CaCl2 and 6% NaCl without CaCl2. However, for cassava chips, the best OD treatments were 45% sucrose without CaCl2 and 3% NaCl with CaCl2. Page's model predicted the OD experimental results with an R2 = 0.94-0.97. Effective diffusivity of water (EDW) and effective diffusivity of solids (EDS) for osmo-dehydrated cassava samples, with and without CaCl2, decreased as the concentration of the osmotic solutions was increased. However, in general, the inverse effect was obtained for plantain samples for EDW and EDS. Use of CaCl2 when applying OD reduced EDW and EDS in plantain and cassava chips. In general, it was observed that when increasing the concentration of the osmotic solution, oil absorption capacity decreased. Treatments that showed the lowest oil absorption were 45% sucrose OD in plantain chips pretreated with CaCl2 (11.49%) and fresh cassava chips with 45% sucrose OD (10.72%). The results and effectiveness will depend on food, process conditions and type of osmotic agent.

Optimization and characterization of an extruded snack based on taro flour (Colocasia esculenta L.) enriched with mango pulp (Mangifera indica L.).

The aim of this study was to optimize and characterize an extruded snack made with taro flour and mango pulp. A central experimental design composed of the following three variables was used: mango pulp proportion (MPP = 0-10 g/100 g) in taro flour, feed moisture content (FMC = 16-30 g/100 g) and extrusion temperature (zone 4 of extruder) (T = 80-150 °C) using a single-screw extruder with a compression screw ratio of 3:1. Increasing FMC values decreased the torque, pressure, specific mechanical energy (SME), expansion index (EI), water solubility index and pH values and increased the residence time, bulk density (BD), hardness and total colour difference. Increasing T values led to a decrease in the torque, pressure, BD and hardness values, while increasing MPP values only caused a significant increase in the hardness values and ß-carotene content and a decrease in the pressure value. The optimal extrusion conditions were T = 135.81 °C, FMC = 18.84 g/100 g and MPP = 7.97 g/100 g, with a desirability value of 0.772, to obtain a snack with EI = 1.52, BD = 0.66 g/cm3, hardness = 24.48 N, ß-carotene content = 99.1 µg/g and SME = 428.54 J/g. The mango pulp is an available and economical source of ß-carotene for the enrichment of extruded expanded taro snacks.

Effect of enzymatic pretreatment on the physical quality of plantain (Musa ssp., group AAB) employing airflow reversal drying.

This work aimed to evaluate the effect of enzymatic pretreatment on the color and texture of plantain (Musa ssp., group AAB) dried by airflow reversal drying. Plantain slices 1.0 cm thick were used. Pretreatment with two commercial enzymes, Pectinex Ultra SPL (Aspergillus aculeatus) and Pectinex 3XL (Aspergillus niger), was performed. Drying kinetics were determined with and without pretreatment at temperatures of 50, 65 and 80 °C using a fixed bed convective dryer. An air speed of 6 m/s, a bed height of 5 cm and either unidirectional flow or airflow reversal (every 15 min) were used for drying. Color and texture were analyzed, and consumer acceptance of the results of the best treatments was determined. Pretreatment with the enzyme A. niger and airflow reversal gave the best drying kinetics and showed the greatest reduction in drying time (59.0%) at 80 °C. The best hardness results were found at 80 °C with A. niger enzymatic pretreatment with both types of air flow. Brightness and hue angle showed that samples pretreated with enzymes and dried at 65 °C had a lighter yellow color compared to non-pretreated samples. Plantain samples enzymatically pretreated and dried at 65 and 80 °C were the most accepted by consumers. This kind of enzymatic pretreatment on plantain could allow the conservation of some physical properties and reduction of drying times relative to the current methodology.