Transfer of the Meat Aroma Precursors (Dimethyl Sulfide, Dimethyl Disulfide and Dimethyl Trisulfide) from Feed to Cooked Pork

Eight pigs were given standard concentrate feed to a live weight of 70 kg. Subsequently half the pigs were controls and were fed the concentrate feed, while the other half of the pigs were fed an experimental diet consisting of the concentrate feed (89 percent of calories) and Brussels sprouts (11 percent of calories) the last 4 weeks before slaughter. Analyses of volatiles in chops and gastro-intestinal contents were performed using solid-phase micro extraction and subsequent characterization by gas chromatography-mass spectrometry. The ratio between the amount of dimethyl sulfide found in the stomach contents from pigs fed Brussels sprouts and the stomach contents from pigs fed the control diet was 9.0, and correspondingly the ratio was 475.5 for dimethyl disulfide and 8.3 for dimethyl trisulfide. The ratio between the amount of dimethyl sulfide found in meat from pigs fed Brussels sprouts and meat from pigs fed the control diet was 14.9, and correspondingly the ratio was 4.8 for dimethyl disulfide and 1.9 for dimethyl trisulfide. Moreover, several other compounds seem to be influenced by feed composition. Finally, the increase in concentration of sulfur compounds in meat in relation to pork aroma is discussed.     

Emulsification properties of proteins extracted from beef lungs in the presence of xanthan gum using a continuous rotor/stator system

The emulsifying properties of beef lung protein concentrate (BLPC) in the presence of xanthan gum were investigated under steady state conditions using a continuous rotor/stator device. Experiments were defined using design of experiments methodology which included formulation and process variables. The influences of xanthan and protein contents were studied first on the properties of the continuous phase, namely viscosity and interfacial tension. Then, emulsion properties, such as average droplet diameter, viscosity and stability against creaming were analyzed using a split-plot design. Experimental results showed that rotation speed played the key role on droplet size reduction, whereas emulsion texture depended slightly on process variables and was governed by the recipe, i.e. by protein and xanthan contents. Conversely, emulsion stability resulted simultaneously from formulation and process factors. Finally, a comparison of BLPC with commercial sodium caseinates in similar recipes under identical operating conditions highlighted the high emulsifying properties of these beef lung proteins.     

High resolution two-dimensional electrophoresis as a tool to differentiate wild from farmed cod (Gadus morhua) and to assess the protein composition of klipfish

Tris and CHAPS–urea extracts from wild and farmed cod muscle and from rehydrated cod klipfish fillets were analyzed by one (1DE) and two-dimensional electrophoresis (2DE). 2DE maps of tris extracts from farmed cod differed from the wild in a series of spots of Mw 35 and 45 kDa. The CHAPS–urea extracts from farmed cod had a several spots of Mw between 100 and 45 kDa, which were hardly detectable in wild cod and very prominent in klipfish. Klipfish was clearly different from the other samples: the myosin heavy chain was hardly detectable in these samples, and the tris extracts contained fewer, and the CHAPS–urea more spots than the corresponding extracts from the raw muscles. Further identification of these potentially diagnostic spots will make it easier the differentiation of farmed from wild cod and the evaluation of klipfish processing on the protein content of the product.     

Flavor Release from a Banana Soft Drink Complex Model System: Evaluation of the Efficiency of Different Adsorbents for Trapping the Released Volatiles During Storage

The main objective of the present study was to evaluate the release of aroma compounds from a banana soft drink complex model system in comparison with their release from simple model systems, each contains individual food ingredients. The effect of different food ingredients (sweeteners and thickeners at different concentrations), used in formulation of the soft drinks, on flavor release from simple model systems containing banana flavor was evaluated separately. The optimum release of isoamyl acetate (the most potent odorant of banana aroma) was observed at a concentration of 10% of each investigated sweetener (sucrose, glucose, and corn syrup). Pectin and xanthane showed the highest release at a concentration of 2.5 and 0.8% w/w, respectively. The level of each ingredient that showed the optimum release of isoamyl acetate was selected and used in formulation of a banana soft drink complex model system. The released volatiles were trapped by tenax and activated carbon. The gas chromatographic-mass spectrometric analysis revealed a gradual decrease (p < 0.05) in the volatile compounds release from the complex banana soft drink model system during storage for 90 days. However, the total content of the volatiles adsorbed by activated carbon trap was higher than that trapped by tenax. The percentage of isoamyl acetate to total volatiles (isoamyl acetate/total volatiles %) was calculated for each sample during storage. A distinct linear correlation was found between the calculated values and storage time (r = 0.97 and 0.92 for volatiles trapped by tenax and activated carbon, respectively). Sample stored for 60 days showed the highest value. These findings confirmed the results of aroma sensory evaluation.     

Oil-in-Water Emulsion as a Model System to Study the Growth of Escherichia coli O157:H7 in a Heterogeneous Food System

Oil‐in‐water emulsions (hexadecane, minimal media [M9], and Tween 20) were used as model system to study the growth of Escherichia coli O157:H7. Stationary‐phase cell density decreased as the hexadecane concentration was increased (0%, 5%, 20%, and 40% [w/v]) and biphasic growth was observed in 40% emulsions supplemented with 0.4% glucose. Thin aggregate fimbriae (curli) were observed using SEM, and a greater percentage (Ps <0.001) of curli‐producing colonies were isolated from 40% emulsions. Heat resistance (55 °C) of emulsion‐grown cells was greater than broth‐grown cells, indicating that growth and physiology under heterogeneous conditions differ from cells grown in liquid.