Patrick Dirinck

Meat quality, fatty acid composition and flavour analysis in Belgian retail beef.

The objective of this study was to evaluate the differences in biochemical, sensorial and quality characteristics of retail beef in Belgium. Four types of beef (Belgian Blue double-muscled, Limousin, Irish and Argentine) and two different muscles (longissimus lumborum and semimembranosus) were bought at the retail level and compared with regard to colour, shear force, collagen content, fatty acid analysis, taste panel evaluation as well as flavour analysis. Belgian Blue and Limousin beef had a paler colour, lower collagen and intramuscular fat contents. Fatty acid profiles were significantly different between the four types, with significantly higher PUFA/SFA and n-6/n-3 ratios for Belgiam Blue and Limousin beef compared to Argentine and Irish beef. There were significant differences between the meat types for taste panel tenderness and shear force, however both measurements did not fully correspond. Flavour analysis by gas chromatography-mass spectrometry as well as sensory analysis demonstrated that Irish and Argentine beef had a higher flavour intensity related to higher contents of volatile compounds. Differences in tenderness and flavour between the meat types were probably affected by differences in ageing time, related to import vs local production of meat.

Flavour characterisation and classification of cheeses by gas chromatographic-mass spectrometric profiling

Abstract As part of a study concerning the biotechnical production of enzyme modified cheese flavours, gas chromatography–mass spectrometry was used for objective measurement of cheese aroma characteristics. In order to obtain the necessary reference information for steering the biotechnical process towards typical cheese flavour characters, such as Gouda and Emmental, the volatile fractions of three Gouda cheeses from different producers and three Emmental cheeses from different origins (Swiss, French and Austrian) were studied. The volatile fractions of the different cheeses were composed of fatty acids, methylketones, lactones, aldehydes and alkenes. Principal component analysis was used for interpretation of the complex semi-quantitative data matrix and allowed classification of the different cheeses. It was observed that the Gouda cheeses from different producers had similar aroma patterns, while more differences were observed between the Emmental cheeses. Austrian Emmental was clearly differentiated from the French and Swiss products.

Selection, application and monitoring of Lactobacillus paracasei strains as adjunct cultures in the production of Gouda-type cheeses

Raw milk cheeses have more intense flavours than cheeses made from pasteurized milk and harbour strains with potential adjunct properties. Two Lactobacillus paracasei strains, R-40926 and R-40937, were selected as potential adjunct cultures from a total of 734 isolates from good quality artisan raw milk Gouda-type cheeses on the basis of their prevalence in different cheese types and/or over several production batches, safety and technological parameters. Conventional culturing, isolation and identification and a combined PCR-DGGE approach using total cheese DNA extracts and DNA extracts obtained from culturable fractions were employed to monitor viability of the introduced adjuncts and their effect on the cheese microbiota. The control cheese made without adjuncts was dominated by members of the starter, i.e. Lactococcus lactis and Leuconostoc pseudomesenteroides. In the cheeses containing either R-40926 or R-40937, the respective adjuncts increased in number as ripening progressed indicating that both strains are well adapted to the cheese environment and can survive in a competitive environment in the presence of a commercial starter culture. Principal component analysis of cheese volatiles determined by steam distillation-extraction and gas chromatography-mass spectrometry could differentiate cheeses made with different concentrations of adjunct R-40926 from the control cheese, and these differences could be correlated to the proteolytic and lipolytic properties of this strain. Collectively, results from microbiological and metabolic analyses indicate that the screening procedure followed throughout this study was successful in delivering potential adjunct candidates to enrich or extend the flavour palette of artisan Gouda-type cheeses under more controlled conditions.

Metabolism of propionic acid by golden delicious apples

Abstract The headspace of whole Golden Delicious apples treated with propionic acid vapour, was analysed by means of GC, after enrichment on Tenax GC, and its c

GLC of the Headspace After Concentration on Tenax GC and of the Essential Oils of Apples, Fresh Celery, Fresh Lovage, Honeysuckle And Ginger Powder

By concentrating the headspace components of intact fruits, vegetables and flowers on Tenax GC, followed by thermal desorption and GC-MS, the composition of the volatiles present can easily be studied. The technique may be applied to materials rich or poor in essential oils, yielding extensive information about the aroma compounds. Moreover, owing to the nondestructive character of the method, repeated sampling is possible. This makes it the method of choice for studying qualitative and quantitative changes in content and composition of the volatiles as function of time, e.g. in physiological and biochemical work.

Pitfalls in Selected Ion Monitoring in Gas-chromatography mass-spectrometry, a theoretical example.

For the routine determination of residues of growth promoters two important types of low-resolution gas chromatograph—mass spectrometer may be distinguished: the ultra-trace full-scan instrument [e.g., the ion trap mass spectrometer (ITS40)] and most other quadrupole apparatus using the selected ion monitoring (SIM) mode for detecting very small amounts (< 1–10 ng). In analysing biological extracts interference between matrix components, present at high concentrations, and analytes, present at low concentrations, should be avoided. In this investigation theoretical examples of pitfalls in SIM due to isotope interference (13C) from matrix components with the analyte were considered. These interferences may lead to false-positive and -negative results and false quantification.

ChemSensor classification of red wines

Abstract In this study the hyphenated technique of automated headspace-solid phase microextraction (HS-SPME) and quadrupole mass spectrometry (MS) as a sensing system was used, in combination with on-line pattern recognition algorithms, for classification of red wines. These ChemSensor classifications based on mass fingerprinting were compared with a time-consuming GC-MS analysis, consisting of headspace-solid phase microextraction, identification, semi-quantitative determination of the wine volatiles and principal component analysis (PCA) of the semi-quantitative data. Good correlations could be observed between both techniques.

Ripening induced in pre-climacteric immature golden delicious apples by propionic and butyric acids

Abstract When intact immature pre-climacteric Golden Delicious apples were treated with propionic or butyric acid vapours, ripening occurred, with attendant respiration climacteric, yellowing and aroma formation in a way almost identical to that when ethylene was used as trigger.

Acetic and propionic acids, inducers of ripening in pre-climacteric golden delicious apples

Abstract When treated with acetic or propionic acid vapours, intact pre-climacteric Golden Delicious apples started ripening prematurely. Experiments with [2− 14 C]propionic acid showed that a small part of the added acid is transformed into [ 14 C]ethylene, and that ripening probably begins in these circumstances as a result of the artificial increase in the endogenous ethylene level. It may be that in unripe apples the small amount of evolved ethylene is mostly derived from simple organic acids, so that the moment at which its triggering concentration is reached depends on the available supply of acids. As this, in turn, is a function of the state of maturity of the fruit, there must be a direct relationship between the start of ripening and the degree of maturity. Thus, even in very unripe apples, catabolic processes are at work or potentially present because of the modified β–oxidation of [1− 14 C]propionic acid observed.