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Bolumar T.,Copenhagen University | Bolumar T.,German Institute of Food Technologies | Andersen M.L.,Copenhagen University | Orlien V.,Copenhagen University
Food Chemistry | Year: 2014

The generation of radicals during high pressure (HP) processing of beef loin and chicken breast was studied by spin trapping and electron spin resonance detection. The pressurization resulted in a higher level of spin adducts in the beef loin than in the chicken breast. It was shown that radicals were formed in the sarcoplasmic and myofibrillar fractions as well as in the non-soluble protein fraction due to the HP treatment, indicating that other radicals than iron-derived radicals were formed, and most likely protein-derived radicals. The addition of iron as well as the natural antioxidants caffeic acid, rosemary extract, and ascorbic acid resulted in an increased formation of radicals during the HP treatment, whereas addition of ethylendiamintetraacetic acid (EDTA) reduced the radical formation. This suggests that iron-species (protein-bound or free) catalyses the formation of radicals when meat systems are submitted to HP. © 2013 Elsevier Ltd. All rights reserved.

Roth S.,University of Hohenheim | Feichtinger J.,Robert Bosch GmbH | Hertel C.,German Institute of Food Technologies
Journal of Applied Microbiology | Year: 2010

Aims: To identify structural components of Bacillus subtilis spores serving as targets for sterilization with microwave induced low-pressure, low-temperature nitrogen-oxygen plasma. Methods and Results: The inactivation of spores followed a biphasic kinetics consisting of a log-linear phase with rapid inactivation followed by a slow inactivation phase. In the course of plasma treatment, damage to DNA, proteins and spore membranes were observed by monitoring the occurrence of auxotrophic mutants, inactivation of catalase (KatX) activity and the leakage of dipicolinic acid, respectively. Spores of the wild-type strain showed the highest resistance to plasma treatment. Spores of mutants defective in nucleotide excision repair (uvrA) and small acid-soluble proteins (ΔsspA ΔsspB) were more sensitive than those defective in the coat protein CotE or spore photoproduct repair (splB). Exclusion of reactive particles and spectral fractions of UV radiation from access to the spores revealed that UV-C radiation is the most effective inactivation agent in the plasma, whereby the splB and ΔcotE mutant spores were equally and slightly less sensitive, respectively, than the wild-type spores. Finally, the extent of damages in the spore DNA determined by quantitative PCR correlated with the spore inactivation. Conclusions: Spore inactivation was efficiently mediated by a combination of DNA damage and protein inactivation. DNA was identified to be the primary target for spore inactivation by UV radiation emitted by the plasma. Coat proteins were found to constitute a protective layer against the action of the plasma. Significance and Impact of the Study: The results provide new evidence to the understanding of plasma sterilization processes. This knowledge supports the identification of useful parameters for novel plasma sterilization equipment to control process safety. © 2009 The Society for Applied Microbiology.

Reineke K.,TU Berlin | Reineke K.,Leibniz Institute for Agricultural Engineering | Schlumbach K.,TU Berlin | Baier D.,TU Berlin | And 3 more authors.
International Journal of Food Microbiology | Year: 2013

High pressure combined with elevated temperatures can produce low acid, commercially sterile and shelf-stable foods. Depending on the temperature and pressure levels applied, bacterial endospores pass through different pathways, which can lead to a pressure-induced germination or inactivation. Regardless of the pathway, Bacillus endospores first release pyridine-2,6-dicarboxylic acid (DPA), which contributes to the low amount of free water in the spore core and is consequently responsible for the spore's high resistance against wet and dry heat. This is therefore the rate-limiting step in the high pressure sterilization process. To evaluate the impact of a broad pressure, temperature and time domain on the DPA release, Bacillus subtilis spores were pressure treated between 0.1 and 900. MPa at between 30 and 80. °C under isothermal isobaric conditions during dwell time. DPA quantification was assessed using HPLC, and samples were taken both immediately and 2. h after the pressure treatment. To obtain a release kinetic for some pressure-temperature conditions, samples were collected between 1. s and 60. min after decompression. A multiresponse kinetic model was then used to derive a model covering all kinetic data. The isorate lines modeled for the DPA release in the chosen pressure-temperature landscape enabled the determination of three distinct zones. (I) For pressures < 600. MPa and temperatures > 50 °C, a 90% DPA release was achievable in less than 5. min and no difference in the amount of DPA was found immediately 2. h after pressurization. This may indicate irreversible damage to the inner spore membrane or membrane proteins. (II) Above 600. MPa the synergism between pressure and temperature diminished, and the treatment temperature alone dominated DPA release.(III) Pressures <600MPa and temperatures <50°C resulted in a retarded release of DPA, with strong increased differences in the amount of DPA released after 2h, which implies a pressure-induced physiological like germination with cortex degradation, which continues after pressure release. Furthermore, at 600MPa and 40°C, a linear relationship was found for the DPA release rate constants ln(kDPA) between 1 and 30min. © 2012 Elsevier B.V.

Reineke K.,TU Berlin | Reineke K.,Leibniz Institute for Agricultural Engineering | Mathys A.,German Institute of Food Technologies | Heinz V.,German Institute of Food Technologies | Knorr D.,TU Berlin
Trends in Microbiology | Year: 2013

It is well known that spore germination and inactivation can be achieved within a broad temperature and pressure range. The existing literature, however, reports contradictory results concerning the effectiveness of different pressure-temperature combinations and the underlying inactivation mechanism(s). Much of the published kinetic data are prone to error as a result of unstable process conditions or an incomplete investigation of the entire inactivation pathway. Here, we review this field of research, and also discuss an inactivation mechanism of at least two steps and propose an inactivation model based on current data. Further, spore resistance properties and matrix interactions are linked to spore inactivation effectiveness. © 2013 Elsevier Ltd.

Stirban A.,Ruhr University Bochum | Stirban A.,Profil Institute for Metabolic Research | Kotsi P.,Ruhr University Bochum | Franke K.,German Institute of Food Technologies | And 4 more authors.
Diabetes Care | Year: 2013

OBJECTIVE-Recent evidence indicates that heat-enhanced food advanced glycation end products (AGEs) adversely affect vascular function. The aim of this study was to examine the acute effects of an oral load of heat-treated, AGE-modified β-lactoglobulins (AGE-BLG) compared with heat-treated, nonglycated BLG (C-BLG) on vascular function in patients with type 2 diabetes mellitus (T2DM). RESEARCH DESIGN AND METHODS-In a double-blind, controlled, randomized, crossover study, 19 patients with T2DM received, on two different occasions, beverages containing either AGE-BLG or C-BLG. We measured macrovascular [brachial ultrasound of flowmediated dilatation (FMD)] and microvascular (laser-Doppler measurements of reactive hyperemia in the hand) functions at baseline (T0), 90 (T90), and 180 (T 180) min. RESULTS-Following the AGE-BLG, FMD decreased at T 90 by 80% from baseline and remained decreased by 42% at T 180 (P < 0.05 vs. baseline, P < 0.05 vs. C-BLG at T 90). By comparison, following C-BLG, FMD decreased by 27% at T 90 and 51% at T180 (P < 0.05 vs. baseline at T 180). A significant decrease in nitrite (T180) and nitrate (T90 and T180), as well as a significant increase in N-carboxymethyllisine, accompanied intake of AGE-BLG. There was no change in microvascular function caused by either beverage. CONCLUSIONS-In patients with T2DM, acute oral administration of a single AGE-modified protein class significantly though transiently impaired macrovascular function in concert with decreased nitric oxide bioavailability. These AGE-related changes were independent of heat treatment. © 2013 by the American Diabetes Association.

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