Date of Award:

12-2008

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Nutrition, Dietetics, and Food Sciences

Department name when degree awarded

Nutrition and Food Sciences

Committee Chair(s)

Silvana Martini

Committee

Silvana Martini

Committee

Marie Walsh

Committee

Donald McMahon

Abstract

The objective of this research was to systematically study the effect of processing conditions on crystallization behavior and destabilization mechanisms of oil-in-water (o/w) emulsions. The effects of oil content (20 and 40 wt %); crystallization temperature (Tc = 10, 5, 0, -5, -10 °C); homogenization conditions, such as high shear (HS), very low pressure homogenization (VLPH), and high pressure homogenization (HPH); and cooling rate (0.2 and 30 °C/min) on both thermal behavior and destabilization mechanisms were analyzed. Docosahexaenoic acid (DHA) was added to VLPH emulsions and its effect on the physicochemical and oxidative stabilities and flavor was studied.

Emulsions with 20% oil were less stable than those with 40% oil with a fast-cooling rate; however, stability increased when the emulsions were cooled slowly. Stability was also affected by oil and droplet size; the smaller the droplet the more stable the system. Smaller droplets (i.e., VLPH, HPH) had an effect on crystallization by delaying the onset of the crystal formation, which was promoted in emulsions with larger droplets (i.e., HS); 20% o/w emulsion crystallization was delayed more than 40%; and in emulsions crystallized using a slow-cooling rate, the crystal formation was less inhibited (i.e., crystals formed at a higher onset temperature [Ton], but at lower Tc) than when using a fast-cooling rate. The formation of lipid crystals either helped stabilize (small droplets) the emulsion and melted in a less fractionated manner or destabilized (big droplets) the emulsion. In addition, fast-cooling rates have greater fractionation than slow-cooling rates.

Due to the greater stability of VLPH emulsions after thawing from being at -10 °C for 3 h, DHA was added to evaluate its effect on flavor (besides the effect on stability) of the emulsion. A descriptive panel was used to evaluate four attributes: oxidized, rancid, fishy, and buttery. The panelists were given samples after 72 h, because contrary to the TBA analysis which showed no significant differences between samples with and without DHA, the fishy smell was evident. The sensory evaluation results showed that there was a significant (p < 0.05) difference in fishiness between the VLPH emulsions with and without DHA, and that the odor was repulsive. No significance was seen for rancid and buttery flavors, and only a marginal significance was seen for oxidized.

Checksum

775d256fc5522d79a10a3cfb37b30d12

Download

Included in

Food Science Commons

Share

COinS

Copyright for this work is retained by the student. If you have any questions regarding the inclusion of this work in the Digital Commons, please email us at .