The objective of this study was to evaluate the protective effects of five different emulsifiers on lipid oxidation in 70% fish oil-in-water emulsions to be used as delivery systems for long chain polyunsaturated omega-3 fatty acids to foods. The emulsifiers were either phospholipid (PL) based or protein based. The PL-based emulsifiers were soy lecithin and two milk PL concentrates (with either 20 or 75% PL). The protein-based emulsifiers were whey protein isolate and sodium caseinate. Lipid oxidation was studied at two pH values (pH 4.5 and 7.0) and results were compared to lipid oxidation in neat fish oil. Lipid oxidation was followed by determination of peroxide values and volatile oxidation products. Emulsions were furthermore imaged by confocal and cryo-scanning electron microscopy. Results showed that emulsions prepared at high pH with proteins oxidized less than or equally to neat oil, whereas, all other emulsions oxidized more. In addition, there was a tendency toward a faster progression in lipid oxidation at low pH compared to high pH for emulsions prepared with protein-based emulsifiers. The opposite was observed for emulsions prepared with PL-based emulsifiers. Hence, at low pH PL-based emulsions may be more suitable as delivery systems than protein-based emulsions. Moreover, the quality of the PLbased emulsifiers seemed to affect lipid oxidation. Practical applications:Results from the present study give an insight into the physical and oxidative stability of 70% fish oil-in-water emulsions prepared with whey protein isolate, sodium caseinate, milk phospholipids, or soy lecithin. The emulsions can be used as delivery systems for fish oil to foods. However, only emulsions prepared with proteins at high pH offered advantages with respect to better oxidative stability during storage compared to neat fish oil. Thus, when fish oil is added to a food product in a delivery emulsion, the type of emulsion used should be carefully considered.

In this study, immediate and long-term effects of high intensity ultrasound on crystallization mechanisms of anhydrous milk fat were examined. Short time (5 s) ultrasound treatment (24 kHz, 300 W/cm 2 , 17.5 J/mL) of milk fat induced crystallization onset at higher temperatures and a longer temperature interval between the crystallization of the high and low melting fractions. The solid fat content in ultrasonicated milk fat was higher during cooling to 5°C and for the first 20 min of incubation at this temperature. After 20 min, the increase diminished, and during further storage, the solid fat content in the ultrasonicated fat remained lower than in the nontreated fat. Ultrasound treatment promoted the formation of spherulite structures and a high degree of size uniformity. Nano-and microscopic changes lead to altered macroscopic properties, where a softer and less brittle milk fat material was obtained, and the effects were sustained during storage. These results contribute to clarify the mechanisms underlying the effects of ultrasound treatment on fat crystallization and shed light on the potential use of ultrasound in the processing chain to tailor products with desired textural properties.

No abstract

No abstract

No abstract