An investigation of process contaminants' formation during the deep frying of breadcrumbs using a bread coat model.

The formation of acrylamide, hydroxymethylfurfural (HMF) and furfural was investigated in a deep fried breadcrumb coat model resembling the coat batter of breaded foods. The influence of the composition of the breadcrumb and the frying conditions on the formation of these contaminants was evaluated. Six wheat-based flour formulations of breadcrumbs were deep fried in sunflower oil at temperatures between 170-200 °C and for frying times of 1-5 minutes. Results showed significant differences in the levels of contaminants according to the concentration of the potential precursors in the breadcrumbs. HMF was influenced by the sugar content in the breadcrumbs whereas levels of acrylamide were significantly correlated with the ratio between asparagine and reducing sugars. Acrylamide, HMF and furfural were directly related to the frying time and temperature. The composition of the breadcrumb and the compounds formed during frying contributed to the total antioxidant capacity of the fried samples. The bread coat model is a useful tool in the formulation of breaded foods since it allows the evaluation of the contribution of breadcrumbs in the formation of process contaminants after frying.

Determination of 10-hydroxystearic, 10-ketostearic, 8-hydroxypalmitic, and 8-ketopalmitic acids in milk fat by solid-phase extraction plus gas chromatography-mass spectrometry.

Fatty acids (FA) bearing oxygenated functions and present in esterified form in triacylglycerols are widespread in nature but very little is known about their occurrence in dairy products. A method based on gas chromatography (with flame ionization detector and mass spectrometry detectors), including the previous isolation of polar FA methyl esters by solid-phase extraction, was applied to quantify oxygenated FA in milk fat. Samples obtained from ewes and goats fed with a variety of oil sources were studied. Fatty acids identified were 8-ketopalmitic, 8-hydroxypalmitic, 10-ketostearic, and mainly 10-hydroxystearic acids. The highest levels of 10-ketostearic acid were obtained in milk from animals fed olive oil (up to 1.5%) and from those fed long-chain n-3 FA-enriched diets (0.5-1.0%). In all samples, 10-hydroxystearic acid, not reported so far in milk, was the second most abundant oxygenated FA (up to 0.8%). The high correlation obtained between contents of 10-ketostearic and 10-hydroxystearic acids would confirm the existence of a common pathway of formation in the rumen, whereas the presence of 8-ketopalmitate and 8-hydroxypalmitate could be putatively attributed to mechanisms of ß-oxidation in the tissues. The influence of cis-9 C18:1 and trans-10 C18:1 as precursors of these compounds in milk and the metabolic pathways involved in their formation are discussed.

Headspace solid-phase microextraction of oil matrices heated at high temperature and phthalate esters determination by gas chromatography multistage mass spectrometry.

A solvent-free analytical approach based on headspace solid-phase microextraction (SPME) of oil matrices heated at high temperatures coupled to gas chromatography with mass spectrometry detector (GC-ion trap) has been developed for the determination of phthalic acid esters (PAEs) in oil matrices without sample manipulation. For this study, three fibers, i.e., 85 microm-polyacrylate (PA), 50/30 microm-divinylbenzene-carboxen-polydimethylsiloxane (DVB/CAR/PDMS) and 100 microm-polydimethylsiloxane (PDMS) were tested. Variables affecting the SPME headspace composition such as incubation sample temperature, sample incubation time and fiber exposition time were optimized. The optimal values found were 250 degrees C for sample incubation temperature and 30 min for incubation and extraction time. PA fiber was not suitable for the lightest polar phthalates which showed poor extraction and repeatability values. PDMS fiber had very poor response for some of the heavier and non-polar phthalates, whereas DVB/CAR/PDMS fiber showed the best response and repeatability values for the majority of the phthalates studied. The main benefit of the analytical method proposed is the absence of sample manipulation and hence avoidance of possible contamination coming from glassware, environment, solvents and samples.

Differences in oxidation kinetics between conjugated and non-conjugated methyl linoleate.

The oxidation kinetics of conjugated methyl linoleate was compared with that of non-conjugated methyl linoleate under mild oxidation conditions (30 degrees C in the dark). Samples of methyl 9-cis,11-trans-linoleate, methyl 10-trans,12-cis linoleate and methyl 9-cis,12-cis linoleate were assayed separately and in mixtures. For comparative purposes, methyl alpha-linolenate and methyl oleate were also used. Two complementary analytical approaches were selected to monitor the progress of oxidation, (1) the traditional follow-up of residual substrate by gas liquid chromatography, and (2) an analytical procedure by high-performance size-exclusion chromatography (HPSEC) for direct measurement of the oxidation compounds formed. The HPSEC method enabled us to quantitate oxidized monomers, dimers and polymers concomitantly in a rapid and direct analysis. Results showed that conjugated methyl linoleate samples oxidized later than their non-conjugated counterparts, and showed a very different oxidation pattern. Thus, formation of oxidized monomers was negligible and the first and major compounds formed were polymerization products. Also, under the conditions used, non-conjugated and conjugated methyl linoleate samples in 1:1 mixtures led to decreased oxidation rate of non-conjugated methyl linoleate and increased oxidation rate of conjugated methyl linoleate. This study supports the view that oxidation kinetics of conjugated dienes differ substantially from that of methylene-interrupted dienes.

A direct and fast method to monitor lipid oxidation progress in model fatty acid methyl esters by high-performance size-exclusion chromatography.

A new method based on high-performance size-exclusion chromatography (HPSEC) is proposed to quantitate primary and secondary oxidation compounds in model fatty acid methyl esters (FAMEs). The method consists on simply injecting an aliquot sample in HPSEC, without preliminary isolation procedures neither addition of standard internal. Four groups of compounds can be quantified, namely, unoxidised FAME, oxidised FAME monomers including hydroperoxides, FAME dimers and FAME polymers. Results showed high repeatability and sensitivity, and substantial advantages versus determination of residual substrate by gas-liquid chromatography. Applicability of the method is shown through selected data obtained by numerous oxidation experiments on pure FAME, mainly methyl linoleate, at ambient and moderate temperatures.

Sensitive and accurate quantitation of monoepoxy fatty acids in thermoxidized oils by gas-liquid chromatography.

A sensitive and accurate methodology for quantitation of monoepoxy fatty acid methyl esters (FAME) by gas-liquid chromatography is proposed. Analytical problems of interfering compounds, ie, methyl monoester of azelaic acid and methyl docosanoate, were solved by a second methylation step with diazomethane and by elimination of nonpolar FAME by adsorption chromatography, respectively. Six monoepoxy FAME were identified and quantitated in olive and sunflower oils heated at 180 degrees C for 15 h: trans-9,10- and cis-9,10-epoxystearate coming from oleate and trans-12,13-, trans-9,10-, cis-12,13- and cis-9,10-epoxyoleate coming from linoleate. Results demonstrated total recovery of monoepoxy compounds after nonpolar FAME elimination with the additional advantage of sample concentration, which allowed quantitation of monoepoxy FAME in the initial oils. Also, repeatability was excellent as relative standard deviations ranged from 2.2 to 5.1% for on-column injection and from 0.1 to 2.0% for automatic split injection.

Bioavailability of n-3 polyunsaturated fatty acids (PUFA) in foods enriched with microencapsulated fish oil.

OBJECTIVE: Incorporation of fish oil into food products provides a means of increasing n-3 fatty acid intake, particularly in populations where fish consumption remains low. The aim of the present study was to evaluate the bioavailability of n-3 PUFA in microencapsulated fish-oil-enriched foods compared with an equal amount of n-3 PUFAs contained in fish oil capsules. METHODS: Twenty-five healthy female volunteers were randomly assigned to one of two groups for the 4-week intervention: one group received 0.9 g of n-3 PUFA/day as fish oil capsule (capsule group), while the second group (food group) received an equal amount of n-3 PUFA/day from enriched foods. Baseline and post-intervention samples were analysed for platelet fatty acid composition. RESULTS: There was no significant difference in the change in platelet arachidonic acid (AA), eicosapentaenoic acid (EPA), or docosahexaenoic acid (DHA) between the two groups following the intervention. CONCLUSIONS: The results indicate that n-3 PUFA from microencapsulated fish-oil-enriched foods are as bioavailable as n-3 PUFA in a capsule. Fortification of foods with microencapsulated fish oil, therefore, offers an effective way of increasing n-3 PUFA intakes and status in line with current dietary recommendations.

Selection of methylation procedures for quantitation of short-chain glycerol-bound compounds formed during thermoxidation.

Five methylation procedures, including base- and acid-catalyzed methods, were tested in thermoxidized methyl linoleate and trilinolein, in order to quantitate major oxidation short-chain glycerol-bound compounds by gas chromatography. Results indicated that transmethylations using KOH in methanol or CH3ONa-CH3OH in tert.-butylmethyl ether were the most appropriate methods, given the excellent reproducibility and practically complete recovery obtained for the compounds of interest, mainly short-chain fatty acids and aldehydic acids. Also, formation of acids from aldehydes during thermoxidation as well as modifications of aldehydic functions under acidic conditions, such as conversion to acetals, were checked using dodecanal as model aldehyde.

Assessments on the digestibility of oxidized compounds from [1-14C] linoleic acid using a combination of chromatographic techniques.

The aim of this study was to evaluate the digestibility coefficients of different groups of oxidized fatty acids by applying a methodology based on chromatographic techniques. After thermoxidative treatment, oxidized labelled linoleic acid was isolated and included at 1% in the experimental diets. Male 250-300 g Wistar rats were fed ad lib for seven days. Lipids extracted from diets and faeces were analyzed using a combination of chromatographic methods and radioactivity measurements to determine the specific digestibilities of four groups of altered fatty acids: oxidized monomers non-polar dimers, oxidized dimers and polymers. Mean digestibility coefficients of oxidized monomers, dimers and polymers were 91.0, 74.5 and 69.8%, respectively. In contrast, non-polar dimers were poorly absorbed. The presence of unaltered labelled fatty acids in faeces indicated that structural modifications may have been taken place prior to absorption, and oxidized fatty acids seem to be the main compounds affected.

Evaluation of hydrolysis and absorption of thermally oxidized olive oil in non-absorbed lipids in the rat.

The aim of this study was to investigate the contribution of hydrolysis and absorption to the reduced digestibility found for heat-oxidized oils. Indirect evaluation methods were designed to assess the hydrolysis and absorption undergone in vivo, based on the analysis of non-absorbed lipids in faeces. The results indicated difficulties in the hydrolysis of complex glyceridic molecules included in heat-oxidized fats. Also, the data suggested that the extension of hydrolysis undergone in vivo was closely dependent on the amount and alteration degree of the dietary fat. This fact was clearly shown specifically for non-altered fatty acids while in the case of non-polar dimer fatty acids the low digestibility value may be associated in part to difficulties during the absorption process.

Changes in endogenous lipid excretion in rats fed diets containing non-heated and thermally oxidized olive oils.

The objective of this study was to determine the effects of diets containing non-heated and thermally oxidized olive oils on fecal endogenous lipids. Male Wistar rats were fed fat-free diets and diets supplemented with 12% non-heated, heated, and a 1:1 mixture of non-heated/heated olive oils. After a 15-day experimental period two groups of fecal lipids from major endogenous sources were quantitated: neutral sterols and fatty acids associated with intestinal microflora action. Fecal endogenous sterols, particularly cholesterol, were significantly higher when diets contained oil, and excretion increased as the dietary oil alteration increased. Similar results were obtained for endogenous fatty acids. Increments of fecal sterols, dependent on oil alteration, could be explained by impairments in triglyceride hydrolysis and subsequent effect on cholesterol micellar solubilization. Moreover, high concentrations of poorly digestible lipids may have led to intestinal microbial modifications.

Modification of triacylglycerides and apolipoprotein B in rats fed diets containing whole milk, skim milk and milk proteins.

The objective of this study was to determine the effects of diets containing milk and milk protein fractions on plasma and hepatic lipids, apolipoprotein B mRNA abundance, and plasma apolipoprotein concentrations and lipoprotein composition. Male rats were fed for 6 wk diets that contained (wt/wt) 76% whole milk (WM diet), 55% skim milk (SMFF diet), 22% casein (CAS diet), 22% whey protein isolate (WHY diet) or 55% skim milk-low fat (SMLF diet). The fat concentration in the SMLF diet was 7%. Butter oil (20%) and corn oil (2%) were added to the SMFF, CAS and WHY diets. Plasma and VLDL triacylglycerides in the WM-fed rats were about half of the level in the groups fed the SMFF and SMLF diets, but not significantly different from those of the WHY-fed group. Hepatic triacylglycerides generally were lower in the WM-fed group than in the other groups. Plasma cholesterol concentration did not differ among groups. Plasma apolipoprotein B was significantly lower in the WM-fed group than in rats fed the SMLF, SMFF or WHY diets. However, apolipoprotein B mRNA abundance in the liver and small intestinal mucosa did not differ due to dietary treatment. Thus the lipemic response due to whole milk is not associated with milk protein fractions and may be due to the presence of fat globule membrane in the diet containing whole milk.