Adjunct starter properties affect characteristic features of Swiss-type cheeses

A large number of microorganisms, both starter microorganisms and non-starter lactic acid bacteria originating from the base milk, or from various contamination sources during cheese manufacture, is associated with cheese ripening and the formation of flavour, texture and aroma. Under controlled conditions, Emmental and Bergk?se, a Gruyère-type cheese variety, were produced from pasteurised milk with standard starters and defined strains of facultatively heterofermentative lactobacilli (FHL), and partly with addition of a defined mixture of enterococci. Lactobacillus casei subsp. casei and L. rhamnosus (two strains each) were selected with respect to their potential for the utilisation of citric acid and ribose as sole energy source. The FHL developed up to 10(8) cfu/g within the first weeks of ripening, and viable counts in mature cheeses were 10(7) cfu/g, independent of the cheese variety. Bergk?se made with addition of L. rhamnosus strains showed a more pronounced proteolysis, resulting in reduced firmness and elasticity values of the cheese body, and FHL strains able to utilise citric acid improved the appearance of the cheeses by increasing the number of small eyes to the desired level. In Emmental cheese, the citric acid (+) strains reduced the intensity of propionic acid formation as the FHL apparently competed with the propionibacteria, and enterococci disappeared completely during maturation. Although further work is needed the study shows that, depending on the cheese variety, particular properties of FHL adjunct starters significantly affect important quality attributes of the resulting cheeses.     

New or lesser known cultivar selection as a tool for sensory and nutritional value enhancement of osmo-convectively dried sour cherries

Taking into consideration the economic importance of sour cherry growing in Europe as well as the arising perspective of novel sour cherry product development, an investigation outlining the processing usefulness of some promising sour cherry cultivars that could lead to a better final product quality was undertaken. Nine new or lesser popular cultivars of sour cherries were compared to ‘English Morello’ with particular consideration given to processing suitability for osmo-convective drying. The quality of raw material was characterized taking into account fruit size, soluble solids content, acidity and pro-health properties. To assess the quality trait stability of individual cultivars, standard deviations were calculated. As a measure of ascertaining the fruits' suitability for drying, the sensory properties of osmo-dried products produced by the examined cultivars were considered. The gathered data demonstrates high seasonal variations in quality traits of the most investigated cultivars, which could well restrict their processing usefulness, especially for osmo-drying, as this product was found highly sensitive to fluctuation of raw material uniformity. Among the tested cultivars ‘Nefris’ emerged the most suitable for processing purposes. Fruits of this cultivar gave high quality dried product of repeatable sensory attributes characterized by significantly better pro-health properties than that of ‘English Morello’.     

Comparison of High-throughput and Manual DNA Extraction Methods for the Qualitative and Quantitative Analysis of MON810 Maize

PCR-based methods are widely used in the European Union and in other countries for the detection, identification, and quantification of genetically modified organisms (GMOs). The preparation of good-quality DNA from plant samples for GMO detection can be a challenging task, particularly if the DNA will be used for quantitative analysis. Two DNA extraction methods, namely manual (NucleoSpin Food kit from Machery-Nagel) and high-throughput partially automated (NucleoMag Plant kit from Machery-Nagel) methods, which utilize different DNA separation principles, were used for the isolation of DNA from maize flour samples. Despite the higher DNA recovery obtained using the high-throughput isolation method, a lower PCR efficiency was achieved, most likely due to the presence of PCR inhibitors in the extracts. We found both DNA extraction methods suitable for GMO analysis.     

Colour of hard cheese

During ripening, body colour of Emmental cheeses was evaluated by tristimulus reflectance measurements. Tristimulus primaries were transformed to the Helmholtz system and into CIELAB-coordinates in order to obtain interpretable results. Apart from lightness decreasing with increasing maturation time, it was found by using both systems that, (1) colourfulness increased continuously up to a cheese age of approximately 10 weeks and then remained constant, and (2) the hue of the cheese body shifted towards a slightly more orange colour in the last stage of ripening. The yellowness index, which represents a one-dimensional measure calculated from tristimulus primaries, is proposed as a simple and adequate measure of cheese body colour, and interrelations with CIELAB-values commonly used in food science are outlined.     

Flux and transmission of β-casein during cold microfiltration of skim milk subjected to different heat treatments

Raw skim milk was subjected to different heat treatments: thermization (65°C, 20 s), pasteurization (72°C, 15 s), and no heat treatment (milk was microfiltered using 1.4-µm membranes at 50°C for bacteria removal; 1.4 MF). The milk (thermized, pasteurized, and 1.4 MF) was cooled and stored at 2°C until processing (at least 24 h) with cold (～6°C) microfiltration using a benchtop crossflow pilot unit (Pall Membralox XLAB 5, Pall Corp., Port Washington, NY) equipped with 0.1-µm nominal pore diameter ceramic Membralox membrane (ET1-070, α-alumina, Pall Corp.). The flux was monitored during the process, and β-casein transmission and removal were calculated. The study aimed to indicate the conditions that should be applied to maximize β-casein passage through the membrane during cold microfiltration (5.6 ± 0.4°C) of skim milk. The proper selection of heat treatment parameters (temperature, time) of the feed before the cold microfiltration process will increase β-casein removal. It is not clear whether the difference in β-casein transmission between 1.4 MF, thermized, and pasteurized milk results from the effect of heat treatment conditions on β-casein dissociation from the casein micelles or on passage of β-casein through the membrane. The values of the major parameters (permeation flux and tangential flow velocity, through the wall shear stress) responsible for a proper membrane separation process were considerably lower than the critical values. It seems that the viscosity of the retentate has a great effect on the performance of the microfiltration membranes for protein separation at refrigerated temperatures.     

Dual ionic conductive membrane for molten carbonate fuel cell

Within this study, the electrochemically inert, molten carbonate fuel cell (MCFC) $\text{γ}$-LiAlO₂ matrix is replaced by oxygen ion conducting ceramics, typical for solid oxide fuel cell (SOFC) application. Such solution leads to synergistic ion transport both by molten carbonate mix (CO₃^2-) and yttria-stabilized zirconia (YSZ) or samaria-doped ceria (SDC) matrix (O^2-).Single unit cell tests confirm that application of hybrid ionic membrane increases the performance (power density) of the MCFC over pure $\text{γ}$-LiAlO₂ for a wide range of operating temperatures (600 °C–750 °C). Cell power density with SDC and YSZ matrices is 2% and 13% higher, respectively, compared to the $\text{γ}$-LiAlO₂ at typical 650 °C operating temperature of MCFC.     

Analysis of Residual Stresses and Dislocation Density of AA6082 Butt Welds Produced by Friction Sir Welding

Metallurgical and Materials Transactions A - The Friction Stir Welding (FSW) method was employed to join AA6082 sheets. The welds were produced with different tool traverse speed (200 and...