Impact of dietary fiber coatings on behavior of protein-stabilized lipid droplets under simulated gastrointestinal conditions.

Multilayer emulsions containing lipid droplets coated by lactoferrin (LF) - anionic polysaccharide layers have improved resistance to environmental stresses (such as pH, salt, and temperature), but their behavior within the gastrointestinal tract (GIT) is currently unknown. The objective of this research was therefore to monitor changes in the physicochemical properties and digestibility of these systems under simulated GIT conditions. Primary emulsions (5% corn oil, 0.5% LF) were prepared using a high-pressure homogenizer. Secondary emulsions (5% corn oil, 0.5% LF, 0.5% polysaccharide) were prepared by incorporating alginate, low methoxyl pectin (LMP) or high methoxyl pectin (HMP) into primary emulsions. Emulsions were then subjected to simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) conditions in sequence. LF, LF-LMP and LF-HMP emulsions were stable to droplet aggregation in the stomach but aggregated in the small intestine, whereas LF-alginate emulsions aggregated in both the stomach and small intestine. The presence of a dietary fiber coating around the initial lipid droplets had little influence on the total extent of lipid digestion in SIF, but LF-alginate emulsions had a slower initial digestion rate than the other emulsions. These results suggest that the dietary fiber coatings may become detached in the small intestine, or that they were permeable to digestive enzymes. Pepsin was found to have little influence on the physical stability or digestibility of the emulsions. The knowledge obtained from this study is important for the design of delivery systems for encapsulation and release of lipophilic bioactive ingredients.

Effect of minor oil constituents on soy oil conjugated linoleic acid production.

Conjugated linoleic acid (CLA) is produced by photoisomerization of soy oil linoleic acid. Yields increase with the degree of oil refining, but the effect of specific minor oil components is not known. Therefore, the objectives were to determine the effect of each soy oil minor component on CLA yields and oxidative stability after processing, to determine the effect of soy oil minor constituent interactions on CLA yields and oxidative stability, and to determine how soy oil Magnesol adsorption pretreatment affects CLA yields. Soy oils with varying levels of peroxides, tocopherols, phospholipids, free fatty acids (FFA), and lutein were each UV irradiated, and the CLA content and oxidative stability were determined. A peroxide value of above 0.8 greatly decreased CLA yields, as did phospholipids above 500 ppm. Tocopherols enhanced CLA production at low levels and reduced yields at high concentrations, while lutein and FFA had little effect. High CLA yields corresponded with a lower oil oxidative stability. The interactions between the minor components showed similar trends as seen in the single component study. These findings were supported by observations that Magnesol adsorption removed large quantities of phospholipids and peroxides from soy oil and greatly increased CLA yields but reduced the oxidative stability. Minor components, particularly peroxides and phospholipids, need to be removed from the oil to optimize CLA yields.

Effect of the degree of processing on soy oil conjugated linoleic acid yields.

Photoirradiation processing can be used to rapidly synthesize conjugated linoleic acid (CLA) in large quantities in soy oil. The objective of this study was to evaluate the effect of the level of refining of soy oil on CLA yields and oxidative properties after photoirradiation. Crude, alkali-refined, alkali-refined bleached, and alkali-refined bleached and deodorized (RBD) soy oils were photoirradiated in a pilot-plant processing system for 12 h with 0.35% iodine catalyst at 47 degrees C. RBD soy oil gave the highest total CLA yield of 16.3% of total oil with 4.3% cis, trans- and trans, cis-CLA isomers. Oxidative stability as measured by weight gain during incubation at 64 degrees C showed that iodine decreased the induction time of soy oil samples by 2-4 days. Photoirradiation processing further decreased the induction time by 2 days as a result of loss of total tocopherols. Iodine addition increased the titratable acidity in all the samples of soy oil. However, the level of refining affects this increase of titratable acidity, and RBD soy oil was found to be the most stable. The study indicates that RBD soy oil was the most suitable candidate for photoirradiation processing. Thus, soy oil should be alkali-refined, bleached, deodorized, and then photoprocessed followed by a secondary adsorption step to remove the iodine catalyst to obtain a RBD CLA-rich soy oil.