Measuring flavor deterioration of fats,oils, dried emulsions and foods

In fats, oils, and simple systems such as model dried emulsions, conventional measurements such as peroxide values and oxygen absorption measurements usually give a valid measure of sample flavor. In real food systems, this is often not the case. Measures of volatile (CO₂, pentane) and nonvolatile (anisidine reactive compounds) peroxide decomposition products often give a better picture of the organoleptic status of a sample. Unusually large amounts of CO₂ are liberated when fats and oils oxidize in the presence of proteins. The implications of this phenomenon are discussed. Presented at the AOCS Meeting, New Orleans, April 1976.     

Effect of sugars and sugar alcohols on autoxidation of safflower oil in emulsions

Oxygen absorption rates were measured on liquid emulsions containing safflower oil and glycerol, sugars or sugar alcohols. Stability to oxidation improved as the level of added compound was increased. Emulsion viscosities were higher, and resistance to creaming was better at the higher concentrations of additives. It is suggested that diffusion of oxygen through the oil-water interface is the rate determining step which is probably slower at high viscosity and in the absence of creaming. Freezedried emulsions containing safflower oil, protein, polyols and anionic surfactant oxidized more rapidly than did those samples in which either polyol or surfactant was omitted. The differences in oxidation rate could be accounted for on the basis of degree of oil dispersion and porosity of the dried particles. No evidence has been found for any true antioxidant or pro-oxidant effect of these compounds.     

The unsaponifiables ofVernonia anthelmintica seed oil

The unsaponifiable fraction ofVernonia anthelmintica seed oil has been studied in detail. Preparative thin layer chromatography (TLC) on argentated plates has revealed that the hydrocarbon fraction contains squalene as well as normal odd chain alkanes among which C₃₁ predominates. A small fraction containing C₁₈–C₂₈ n-alcohols was also found. The sterol fraction made up the bulk of the unsaponifiables (66%). This fraction contained at least six sterols but two of these accounted for over 90% of the total. The sterols occur in the oil in the esterified form; gas liquid chromatography shows that they are preferentially esterified to linoleic acid. These esters have been isolated by column chromatography on silica gel and have been separated by preparative TLC. Purification by preparative TLC followed by high resolution mass spectrometry has shown that empirical formulas of the two most abundant sterols are C₂₉H₄₆O and C₂₉H₄₈O. The latter corresponds to the already reported Δ⁷-avenasterol. The former is a new sterol having three double bonds and a stigmastane backbone. Presented in part at the AOCS Meeting, New Orleans, April 1970.     

Effect of amino acids on the autoxidation of safflower oil in emulsions

Oxygen absorption rates were measured on liquid emulsions containing safflower oil and various amino acids. The antioxidant effects of the several amino acids were quite variable depending on the type of emulsifier used, the pH of the system and the presence of added sugar. Preliminary tests with Maillard reaction products obtained by heating dextrose with lysine showed little stabilizing effect. In freeze-dried emulsions, methionine, threonine, lysine and histidine all exhibited antioxidant activity. With sodium caseinate as the matrix, methionine was much better than any of the other amino acids. The inclusion of sugar enhanced the rate of oxidation. Porosity measurements on the freeze-dried powders revealed that oxygen diffusion was not rate-determining. When xanthan gum was used to replace caseinate in these dried emulsions, oxidation rates increased.     

Polymerization inhibitors for polyunsaturated oils

Several edible anionic surfactants were found to function as polymerization inhibitors for safflower oil. The most effective additive was the sodium salt of phosphated mono- and diglycerides. Additional inhibitors included sodium diacetyltartaric acid esters of mono- and diglycerides, sodium stearoyl-2-lactylate, sodium stearyl fumarate, sodium succinoylated mono- and diglycerides, dioctyl sodium sulfosuccinate, and sodium sulfoacetate esters of mono- and diglycerides. It is suggested that these surfactants behave in a manner similar to methyl polysiloxane, as oxygen barriers at the oil-air interface. This view is supported by data showing that in the free acid, oil soluble form their functionality is minimal. But when they are neutralized to form the sodium salts their effectiveness is markedly enhanced. One of seven papers presented in the symposium “Biological Significance of Autoxidized and Polymerized Oils,” JOCS-AOCS Joint Meeting, Los Angeles, April 1972.     

Deciding probabilistic automata weak bisimulation: theory and practice

Weak probabilistic bisimulation on probabilistic automata can be decided by an algorithm that needs to check a polynomial number of linear programming problems encoding weak transitions. It is hence of polynomial complexity. This paper discusses the specific complexity class of the weak probabilistic bisimulation problem, and it considers several practical algorithms and linear programming problem transformations that enable an efficient solution. We then discuss two different implementations of a probabilistic automata weak probabilistic bisimulation minimizer, one of them employing SAT modulo linear arithmetic as the solver technology. Empirical results demonstrate the effectiveness of the minimization approach on standard benchmarks, also highlighting the benefits of compositional minimization.     

Autoxidation products from cholesterol

Thin-layer chromatography and gas-liquid chromatography were used to separate and identify products from the autoxidation of cholesterol. Both cholesterol-a-epoxide and 1,4-cholestadien-3-one were found. In addition, several other compounds, identified also by previous workers, were shown to be present. Autoxidation in bulk was quite slow at 82C, requiring several weeks for development of detectable quantities of decomposition products. The reaction could be accelerated by irradiation with ultraviolet light or by heating the sterol above its melting point.     

Measurement of emulsion stability by pulsed nuclear magnetic resonance (NMR)

The stability of emulsions can be measured rapidly and accurately using pulsed nuclear magnetic resonance (NMR).