Aroma-active secondary oxidation products of butter

Butter contains vitamins, minerals and unsaturated lipids, such as polyunsaturated fatty acids (PUFA) and conjugated linoleic acids (CLAs). However the oxidative stability and consequently the shelf-life of milk products are inversely correlated with their PUFA and CLA content. The objective of this study is the evaluation of the oxidative stability and sensory quality of PUFA/CLA-enriched butter versus conventional butter, with both types of butter being produced at ALP. For this purpose, new chemical and sensory-based methods will be developed, as well holistic complementary methods. This paper focuses on a preliminary study achieved using conventional butter, subjected to a long storage and to oxygen and light exposure, to develop a gas chromatography olfactometry (GC-O) method able to detect the aroma-active compounds originated from oxidation. This will be one of the methods used for the evaluation of the oxidative stability of PUFA/CLA-enriched butter

Water content of roasted coffee: impact on grinding behaviour, extraction, and aroma retention

Normal and long time roasting trials were carried out on industrial scale. Different amounts of water were applied during quenching, resulting in water contents in the range of 2.3-8.8g/100gwb. Coffees were ground immediately after cooling, and after equilibration times of 6 and 24h. Particle size distribution of ground coffees, percolation time, and extraction properties were investigated on an espresso coffee machine. Coffees ground after 24h resting time were subjected to storage trials to determine aroma stability as influenced by water content. Coffees with high moisture content exhibited coarser particles upon grinding, and equilibration time prior to grinding was needed for coffees with high water content to improve grinding results. Coffees with low water content did not exhibit this time dependency prior to grinding. Coffees with low water content were extracted more effectively than high moisture coffees, and percolation was slower. During open and closed storage, evolution of hexanal and sulfides was highly sensitive to water content. However, differences in evolution of other aroma compounds were found during closed storage only, where moisture content had a negative impact on aroma stability of the coffees subjected to investigatio

Analytical Chemistry in Food Science

Analytical chemistry presents a traditional and important tool in food science. Its development grew out of governmental food control to verify food composition and wholesomeness. In modern food chemistry, analytical methods are applied to study food constituents, additives and contaminants and their interactions and reactions during processing and storage. Research activities of the Food Chemistry group at ETH comprise investigations on carbohydrates and on chiral flavour compounds. Experimental work in food technology relies on simple analytical methods that are suitable for large series of processing trials. Such methods are used by the Food Technology group to optimize lipid stability of heat sterilized meat and hot-air roasted nuts. Analytical chemistry is taught at ETH in lectures and laboratory courses to all food science majors

Practical Experience with 'Electronic Nose' Systems for Monitoring the Quality of Dairy Products

The present paper reports some practical experience acquired by testing five sensor technologies and four instruments over approximately one year with Swiss Emmental cheese samples of different stage of ripening. Up to now, the metal-oxide semiconductor (MOS) technology has given the best discrimination between the measured samples. However, sensors of this type seem to be damaged by short-chain fatty acids released from Swiss Emmental cheese. Organic conducting polymer sensors showed a poor sensitivity to volatile components of cheese, the main problem being a rapid drift of the sensors. The response of quartz microbalance sensors was too weak to detect differences between cheese samples. Discrimination using a newly designed mass-spectrometry system was difficult due to the low sensitivity of this instrument for the volatile compounds of cheese. Metal-oxide semiconductor field effect transistor sensors did not give good discrimination between the samples. However, their combination with MOS sensors seems to produce a favourable system for application in cheese evaluation. Further studies with other types of cheese and other dairy products are still necessary to define reliable and practical applications of this analytical tool in the dairy industry

Acrylamide in almond products

Acrylamide was determined in 86 different almond products, such as roasted almonds, almond-containing bakery products, raw almonds, and marzipan. The highest acrylamide concentrations were found in dark roasted almonds, while only moderate acrylamide contents were determined in bakery products. Roasting experiments under different process conditions showed that acrylamide increases with time and that temperature has a much stronger effect on acrylamide formation than time. During roasting reducing sugars are consumed faster and to a larger extent than free asparagine, suggesting that the content of reducing sugars may be a critical factor for acrylamide formation in roasted almonds. Acrylamide was found to decrease in roasted almonds during storage at room temperatur

TEXTURE AND MICROSTRUCTURE CHARACTERIZATION OF PASTES RECONSTITUTED FROM DRUM-DRIED FLAKES OF YAM (DIOSCOREA SPP.)

Drum-dried flakes were processed from two popular varieties of the tropical tuber crop yam species D. cayenensis-rotundata and reconstituted to dough like pastes, the most consumed form in Côte d’Ivoire. Pastes from flakes were compared to that prepared by a standardized laboratory procedure. The structure and texture of the pastes was characterized by instrumental and sensory analysis as well as microscopy. Large differences were found between the yam pastes from the two varieties in terms of changes in textural properties and structure upon the drum-drying processing. Reconstituted paste from the variety Assawa was perceived by the sensory panel as more springy and chewy whereas that of Kponan was less extensible and sticky. Although, no significant difference was found in mechanical properties, in terms of firmness, elasticity and adhesion of pastes. Light micrographs revealed that the variety Kponan was less susceptible to cell rupturing

High aldosterone-to-renin variants of CYP11B2 and pregnancy outcome

Background. Increased aldosterone concentrations and volume expansion of normal pregnancies are hallmarks of normal pregnancies and blunted in pre-eclampsia. Accordingly, we hypothesized an active mineralocorticoid system to protect from pre-eclampsia. Methods. In pregnant women (normotensive n = 44; pre-eclamptic n = 48), blood pressure, urinary tetrahydro-aldosterone excretion and activating polymorphisms (SF-1 site and intron 2) of the aldosterone synthase gene (CYP11B2) were determined; 185 non-pregnant normotensive individuals served as control. Amino acid-changing polymorphisms of the DNA- and agonist-binding regions of the mineralocorticoid receptor were evaluated by RT-PCR, SSCP and sequencing. Results. Urinary tetrahydro-aldosterone excretion was reduced in pre-eclampsia as compared to normal pregnancy (P < 0.05). It inversely correlated with blood pressure (r = 0.99, P < 0.04). Homozygosity for activating CYP11B2 polymorphisms was preferably present in normotensive as compared to pre-eclamptic pregnancies, identified (intron 2, P = 0.005; SF-1 site, P = 0.016). Two mutant haplotypes decreased the risk of developing pre-eclampsia (RR 0.16; CI 0.05-0.54; P < 0.001). In contrast, intron 2 wild type predisposed to pre-eclampsia (P < 0.0015). No functional mineralocorticoid receptor mutant has been observed. Conclusions. High aldosterone availability is associated with lower maternal blood pressure. In line with this observation, gain-of-function variants of the CYP11B2 reduce the risk of developing pre-eclampsia. Mutants of the mineralocorticoid receptor cannot explain the frequent syndrome of pre-eclampsi

Potential for acrylamide formation in potatoes: data from the 2003 harvest

Reducing sugars, free amino acids, and the potential for acrylamide formation were determined in more than 50 potato samples from the 2003 harvest in Switzerland. The reducing sugar content strongly correlated with acrylamide, whereas no correlation was found between acrylamide and free asparagine or the pool of free amino acids. The reducing sugar contents and the acrylamide potentials were higher in most of the cultivars tested than in the samples from 2002. This was probably due to the hot and dry summer of 2003. Monitoring sugars and amino acids during heating at 120°C and 180°C showed that glucose and fructose reacted much faster than sucrose and the amino acids. Glutamine was consumed to a larger extent than any of the other amino acids. During prolonged storage, the reducing sugars decreased considerably while only moderate changes in the free amino acids were observed. Altogether, glucose and fructose remain the critical factors for acrylamide formation in potatoes and represent the most feasible way of reducing the formation of acrylamide in potato product

High Salt Intake Down-Regulates Colonic Mineralocorticoid Receptors, Epithelial Sodium Channels and 11β-Hydroxysteroid Dehydrogenase Type 2

Besides the kidneys, the gastrointestinal tract is the principal organ responsible for sodium homeostasis. For sodium transport across the cell membranes the epithelial sodium channel (ENaC) is of pivotal relevance. The ENaC is mainly regulated by mineralocorticoid receptor mediated actions. The MR activation by endogenous 11β-hydroxy-glucocorticoids is modulated by the 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2). Here we present evidence for intestinal segment specific 11β-HSD2 expression and hypothesize that a high salt intake and/or uninephrectomy (UNX) affects colonic 11β-HSD2, MR and ENaC expression. The 11β-HSD2 activity was measured by means of 3H-corticosterone conversion into 3H-11-dehydrocorticosterone in Sprague Dawley rats on a normal and high salt diet. The activity increased steadily from the ileum to the distal colon by a factor of about 3, an observation in line with the relevance of the distal colon for sodium handling. High salt intake diminished mRNA and protein of 11β-HSD2 by about 50% (p<0.001) and reduced the expression of the MR (p<0.01). The functionally relevant ENaC-β and ENaC-γ expression, a measure of mineralocorticoid action, diminished by more than 50% by high salt intake (p<0.001). The observed changes were present in rats with and without UNX. Thus, colonic epithelial cells appear to contribute to the protective armamentarium of the mammalian body against salt overload, a mechanism not modulated by UNX