A pinboard by
Thanh Vu

PhD Candidate, University of Massachusetts Amherst


Fundamental knowledge to develop technologies increasing food quality and reducing food waste

My research provides novel scientific knowledge on lipid oxidation in low moisture snacks which contributes a high saturated fat intake to American diet. Manufacturers can utilize my research findings to develop strategies to promote healthiness as well as increase shelf life of food products. Understanding oxidation mechanism allows manufacturers to reduce amount of saturated fat, which eventually reduce a risk of cardiovascular disease, and incorporate lipid bio active compounds into low moisture foods. In addition, increasing shelf life of food products is one of strategies to reduce food waste, which is currently a global challenge in sustainable development goals.

My study is the first one to address a relation between lipid physical properties and chemically oxidation stability in low moisture food system. A low moisture cracker is used as a model system. The chemical side of this story can be studied by many traditional lipid oxidation techniques such as gas chromatography and high performance liquid chromatography. However, the physical characterization is measured by cutting edge techniques, namedly spectrofluorometer and fluorescent molecular rotors. My findings indicated that the confinement of fat network inside low moisture cracker system impact on its chemically oxidative stability.

Interestingly, the oxidation fate of low moisture model cracker was different from those in oil-in-water emulsion and bulk oil. In low moisture cracker, fat was oxidized firstly into lipid hydroperoxides. It took these hydroperoxides up to several months to decompose into secondary oxidation products. Meanwhile, in emulsion or bulk oil systems, lipid hydroperoxides and secondary oxidation products were formed almost at the same time. Life time of lipid hydroperoxides in crackers depended on moisture and acidity of the cracker matrix.

Lastly, shelf life of crackers could be increased by using natural additives. Compared to protein, reducing sugars were found to increase oxidative stability of crackers. A good example of reducing sugar is maltose, which is also known as malt sugar or a product from starch hydrolysis. Hence, reducing sugars could be used as natural antioxidants to replace artificial compounds, such as butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ) which have been widely used as antioxidants in food industry.


Lipid oxidation in corn oil-in-water emulsions stabilized by casein, whey protein isolate, and soy protein isolate.

Abstract: Proteins can be used to produce cationic oil-in-water emulsion droplets at pH 3.0 that have high oxidative stability. This research investigated differences in the physical properties and oxidative stability of corn oil-in-water emulsions stabilized by casein, whey protein isolate (WPI), or soy protein isolate (SPI) at pH 3.0. Emulsions were prepared with 5% corn oil and 0.2-1.5% protein. Physically stable, monomodal emulsions were prepared with 1.5% casein, 1.0 or 1.5% SPI, and > or =0.5% WPI. The oxidative stability of the different protein-stabilized emulsions was in the order of casein > WPI > SPI as determined by monitoring both lipid hydroperoxide and headspace hexanal formation. The degree of positive charge on the protein-stabilized emulsion droplets was not the only factor involved in the inhibition of lipid oxidation because the charge of the emulsion droplets (WPI > casein > or = SPI) did not parallel oxidative stability. Other potential reasons for differences in oxidative stability of the protein-stabilized emulsions include differences in interfacial film thickness, protein chelating properties, and differences in free radical scavenging amino acids. This research shows that differences can be seen in the oxidative stability of protein-stabilized emulsions; however, further research is needed to determine the mechanisms for these differences.

Pub.: 06 Mar '03, Pinned: 08 Aug '17

Antioxidant activity of cysteine, tryptophan, and methionine residues in continuous phase beta-lactoglobulin in oil-in-water emulsions.

Abstract: Proteins dispersed in the continuous phase of oil-in-water emulsions are capable of inhibiting lipid oxidation reactions. The antioxidant activity of these proteins is thought to encompass both free radical scavenging by amino acid residues and chelation of prooxidative transition metals; however, the precise mechanism by which this occurs remains unclear. In this study, the oxidative stability of cysteine, tryptophan, and methionine residues in continuous phase beta-lactoglobulin (beta-Lg) in a Brij-stabilized menhaden oil-in-water emulsion was determined. The presence of low concentrations of continuous phase beta-Lg (250 and 750 microg/mL) significantly inhibited lipid oxidation as determined by lipid hydroperoxides and thiobarbituric acid reactive substances analysis. It was observed that cysteine oxidized before tryptophan in beta-Lg, and both residues oxidized before lipid oxidation could be detected. No oxidation of the methionine residues of beta-Lg was observed despite its reported high oxidative susceptibility. It is conceivable that surface exposure of amino acid residues greatly affects their oxidation kinetics, which may explain why some residues are preferentially oxidized relative to others. Further elucidation of the mechanisms governing free radical scavenging of amino acids could lead to more effective applications of proteins as antioxidants within oil-in-water food emulsions.

Pub.: 22 Dec '05, Pinned: 29 Aug '17