Antioxidant activity of phenolic compounds in sunflower oil‐in‐water emulsions containing sodium caseinate and lactose

Abstract

The aim of this work was to study the evolution of oxidation and the efficiency of phenolic antioxidants in sunflower oil-in-water emulsions containing sodium caseinate and lactose (Cas-Lac) or stabilized by . Two groups of phenolic antioxidants which are structurally similar were tested, i.e. (1) a-tocopherol and its water-soluble analogue, Trolox; and (2) gallic acid and its ester derivatives propyl gallate and dodecyl gallate. Emulsion samples were oxidized at 40 7C and the progress of oxidation was followed through quantitation of oxidized triacylglycerol monomers, dimers and oligomers. Results showed that Cas-Lac emulsions were more stable to oxidation than T-20 emulsions. In both types of emulsions, the most protective antioxidants were the compounds of lower polarity, namely, a-tocopherol and dodecyl gallate. It was also found that substantial amounts of a-tocopherol coexisted with significant polymerization, which was indicative of the heterogeneity of oxidation, i.e. differences of oxidation rate in oil droplets.

One-pot esterification and amidation of phenolic acids

“…In these reactions, a by-product was formed in 10-20% yields. From the 1 H and 13 C NMR analyses, the structure of the by-product was established to be tert-butyl (E)-4-tertbutoxycarbonyloxy-3-methoxy-cinnamate (2, Fig. 1).…”

“…NMR, LC-MS, and FT-IR analyses were performed at the CREFAS (Collaborated Research Center for Food Functions, Faculty of Agriculture, Shinshu University). NMR spectra in the indicated solvents were recorded using a Bruker DRX500 spectrometer (Bruker BioSpin Corp., Billerica, MA) at 500 MHz for 1 H and 126 MHz for 13 C NMR or a Varian UNITY plus-400 (Varian Inc., Palo Alto, CA) at 400 MHz for 1 H and 100 MHz for 13 C NMR at 25 °C. Chemical shifts were referenced to the signal of TMS as the internal standard.…”

“…29 An isotopomer of CAPE is an ideal internal standard and a metabolic tracer. In general, an isotopomer is chemically synthesized and labeled with a stable isotope of 13 C. A high-yield method is needed for the synthesis of 13 C-labeled compounds because of the expensiveness of the labeled compounds. As a practical example of our convenient developed method, the isotopomers of CAPE were synthesized from 13 C-labeled caffeic acid and 2-phenethyl alcohol in excellent yields.…”

A follow-up oxidation study in dried microencapsulated oils under the accelerated conditions of the Rancimat test

“…in the liquid system, containing the same components as those used in the present study (Velasco, Dobarganes, & Márquez-Ruiz, 2004). As opposed to its more lipophilic homologue a-tocopherol, it has been well documented that Trolox loses considerably its antioxidant effectiveness when tested from bulk oils to oil-in-water emulsions.…”

Structure–antioxidant activity relationships of o-hydroxyl, o-methoxy, and alkyl ester derivatives of p-hydroxybenzoic acid

“…As can be seen in Table 2, the overall hydrophobicity of the phenolic ring has increased more by introducing alkyl ester than methoxy groups. In addition, the nature of emulsifier used to stabilize the emulsion can greatly affect the contribution of antioxidant incorporated to the water-oil interface (Velasco, Dobarganes, & Marquez-Ruiz, 2004). Soy protein isolate is considered to be a negatively charged emulsifier at neutral pH.…”