Stability of palm olein (PO) and a blend 50% palm olein ⁄ 50% canola oil (POC) during deep-fat frying at 180°C of French fries (FF) or chicken nuggets (CN) was studied through the determination of physical and chemical parameters in the fresh and used oils. Degradation at the end of the study resulted in total polar compounds of 12-13.5% for PO and 11.5-14.5% for POC and viscosity of 65-123.3 cP for PO and 63-72.8 cP for POC. Lower peroxide values (5.33-6.32) were obtained for the blend (PO had 5.21-8.55). Food type affected colour parameters and p-anisidine value of the oils. For CN, the lowest fat content and higher hardness were obtained when they were fried in PO. CN caused a faster deterioration in the oils, in comparison with FF, especially in POC. Gas chromatography allowed to observe differences in fatty acids composition for both used oils.

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Sensory analysis is a valuable tool used to determine the effect of a formulation or process on the perception of a product. In this study, triangle tests were performed to determine differences between fried foods cooked in fresh palm olein and a fresh blend of canola oil and palm olein (50/50) and between food products fried in fresh oil and those fried in used oil. Freshness did not cause a significant difference between french fries and chicken nuggets, as evaluated by 72 nontrained judges (p > 0.05). However, the kind of oil had an effect on the sensory perception of the fried foods, in particular the flavor and texture of both products (p < 0.05).

The present work analyzed the properties of two concentrated milks, as well as the influence of the reconstituted type on some properties of milk powder. Two sets of milk with high solids content (43-60% w/w) were employed; one set was concentrated by evaporation of liquid milk, while the other was prepared by reconstitution of milk powder. Both concentrated milks were characterized at the different solids contents, measuring flow and physicochemical properties; finding a non-Newtonian behavior well fitted by the Power law model. The bh color parameter, density and consistency coefficient increased, while luminosity, redness and flow index decreased as a function of solids concentration. Lately, the reconstituted milk with four levels of concentration was spray dried, and their properties, such as apparent density, color, moisture, particle size and rehydration, were determined. Based on properties of reconstituted and powder milks, other engineering parameters, such as drop diameter and heat transfer coefficient, were equated, in order to relate physical properties for dryer design. PRACTICAL APPLICATIONSThis work is not a sophisticated study. It covers the fundamentals and practical aspects of a very important food process operation, drying of milk. Most of the works on food preservation methods have been conducted to analyze microbiological, physicochemical and processing aspects, and very few studies have been carried out to analyze the transport phenomena in spray drying, passing by concentration aspects and properties. Thus, this practical and useful work applies momentum, heat and mass transfer approaches to quantify the flow properties of two concentrates and how they influence some physical properties for milk powder and two design parameters for the dryer performance. bs_bs_banner Journal of Food Process Engineering