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Shayanfar S.,German institute of food technologies DIL | Bodbodak S.,Gorgan University of Agricultural Sciences and Natural Resources
Journal of Food Science and Technology | Year: 2014

Grape contains a great deal of tartaric acid and minerals such as Potassium and Calcium which during ripening of grape increase in concentrations and result in potassium and calcium tartrate precipitation in grape juice. There have been different methods introduced for de-tartration but none of them have been completely successful. These methods can be categorized into two different groups of physicochemical and instrumental methods. In this study application of cold treatment, cream of tartar (Potassium bitartrate), Carboxymethyl Cellulose (CMC), and Mannoprotein were investigated. Then all these samples were stored at 5 °C to stimulate tartrate crystals precipitation and were investigated for color indices change, the amount of sediments, acidity, pH and taste. Among these methods addition of Mannoprotein and CMC were proved to have ability in stabilizing tartrate crystals in red grape juice. © 2012, Association of Food Scientists & Technologists (India).


Dong P.,China Agricultural University | Dong P.,National Engineering Research Center for Fruits and Vegetables Processing | Dong P.,Key Laboratory of Fruits and Vegetables Processing | Dong P.,German Institute of Food Technologies DIL | And 5 more authors.
Frontiers in Microbiology | Year: 2015

Ultra high pressure homogenization (UHPH) opens up new areas for dynamic high pressure assisted thermal sterilization of liquids. Bacillus amyloliquefaciens spores are resistant to high isostatic pressure and temperature and were suggested as potential surrogate for high pressure thermal sterilization validation. B. amyloliquefaciens spores suspended in PBS buffer (0.01 M, pH 7.0), low fat milk (1.5%, pH 6.7) and whole milk (3.5%, pH 6.7) at initial concentration of ~106 CFU/mL were subjected to UHPH treatments at 200, 300 and 350 MPa with an inlet temperature at ~80 °C. Thermal inactivation kinetics of B. amyloliquefaciens spores in PBS and milk were assessed with thin wall glass capillaries and modeled using first-order and Weibull models. The residence time during UHPH treatments was estimated to determine the contribution of temperature to spore inactivation by UHPH. No sublethal injury was detected after UHPH treatments using sodium chloride as selective component in the nutrient agar medium. The inactivation profiles of spores in PBS buffer and milk were compared and fat provided no clear protective effect for spores against treatments. Treatment at 200 MPa with valve temperatures lower than 125 °C caused no reduction of spores. A reduction of 3.5 log10 CFU/mL of B. amyloliquefaciens spores was achieved by treatment at 350 MPa with a valve temperature higher than 150 °C. The modeled thermal inactivation and observed inactivation during UHPH treatments suggest that temperature could be the main lethal effect driving inactivation. © 2015 Dong, Georget, Aganovic, Heinz and Mathys.


Georget E.,German Institute of Food Technologies DIL | Kapoor S.,TU Dortmund | Winter R.,TU Dortmund | Reineke K.,Leibniz Institute for Agricultural Engineering | And 5 more authors.
Food Microbiology | Year: 2014

Bacterial spores are a major concern for food safety due to their high resistance to conventional preservation hurdles. Innovative hurdles can trigger bacterial spore germination or inactivate them. In this work, Geobacillus stearothermophilus spore high pressure (HP) germination and inactivation mechanisms were investigated by in situ infrared spectroscopy (FT-IR) and fluorometry. G.stearothermophilus spores' inner membrane (IM) was stained with Laurdan fluorescent dye. Time-dependent FT-IR and fluorescence spectra were recorded in situ under pressure at different temperatures. The Laurdan spectrum is affected by the lipid packing and level of hydration, and provided information on the IM state through the Laurdan generalized polarization. Changes in the -CH2 and -CH3 asymmetric stretching bands, characteristic of lipids, and in the amide I' band region, characteristic of proteins' secondary structure elements, enabled evaluation of the impact of HP on endospores lipid and protein structures. These studies were complemented by ex situ analyses (plate counts and microscopy). The methods applied showed high potential to identify germination mechanisms, particularly associated to the IM. Germination up to 3 log10 was achieved at 200MPa and 55°C. A molecular-level understanding of these mechanisms is important for the development and validation of multi-hurdle approaches to achieve commercial sterility. © 2014 Elsevier Ltd.


Georget E.,German Institute of Food Technologies DIL | Georget E.,Leibniz University of Hanover | Sevenich R.,TU Berlin | Reineke K.,Leibniz Institute for Agricultural Engineering | And 5 more authors.
Innovative Food Science and Emerging Technologies | Year: 2015

The benefits of high pressure processing (HPP) for microbial inactivation in food production include reduced thermal treatment and minimized effects on sensory and nutritional profiles. These benefits have resulted in increasing commercial production of high pressure pasteurized foods. In this review, the current state of the art in terms of vegetative cell and bacterial spore inactivation by HPP in complex food matrices is assessed with an emphasis on mechanisms of inactivation and treatment of products that have low or non-uniform water activity (aw) profiles. Low aw can be the result of a high concentration in solutes, the presence of oils/fats, or the physical removal of water through dehydration. Microbial inactivation in low aw environments remains a particular challenge for HPP and studies on microbial inactivation observed in the different types of low aw food matrices are reviewed in detail. Industrial relevance HPP-treated food products with low aw have been on the market since the nineties, but the mechanisms of microbial inactivation at low aw are still not well understood, which hinders the development of new applications in low or inhomogeneous aw food. This review summarizes the state of the art in terms of HPP microbial inactivation mechanisms in model systems and various low aw food environments. Thereby, it identifies existing and potential new applications as well as the current gaps and future research needs. © 2014 Elsevier Ltd. All rights reserved.


Georget E.,German Institute of Food Technologies DIL | Georget E.,Leibniz University of Hanover | Miller B.,German Institute of Food Technologies DIL | Aganovic K.,German Institute of Food Technologies DIL | And 3 more authors.
Innovative Food Science and Emerging Technologies | Year: 2014

A new generation of high pressure homogenizers reaching up to 400 MPa offers opportunities for spore inactivation and high pressure sterilization of foods. A Stansted Fluid Power ultra-high pressure homogenization (UHPH) unit was tested to inactivate bacterial spores in a model buffer system. Bacillus subtilis PS832 and Geobacillus stearothermophilus ATCC7953 spores' thermal resistances were assessed (D, z-value and Ea). The pressure and valve temperature were monitored during UHPH. Residence times under pressure and high temperature were estimated and enabled comparison with thermal inactivation, indicating the estimated thermal contribution to inactivation. Spore germination was also assessed but no germination was observed. Up to five log10 B. subtilis and two log10 G. stearothermophilus spores were inactivated by the harshest treatments (> 300 MPa -Tvalve > 145 °C for ~ 0.24 s). The inactivation profiles were similar to the predicted thermal inactivation suggesting that the valve temperature might be a dominant parameter leading to bacterial spore inactivation. Industrial relevance This work showed the UHPH potential for spore inactivation and the need of highly thermoresistant surrogates for process validation, for instance, G. stearothermophilus ATCC7953 spores. Both these findings are highly relevant for industrial application as, to date, no surrogate for this process was suggested while the first patents for the technology transfer to industry are being issued. © 2014 Elsevier Ltd.


Seitter M.,University of Hohenheim | Geng B.,University of Hohenheim | Hertel C.,German Institute of Food Technologies DIL
International Journal of Food Microbiology | Year: 2011

In connection with a study on the DNA microarray based detection of genes involved in safety and technologically relevant properties (Seitter (née Resch) et al., 2011), food-associated coagulase-negative staphylococci (CNS) were investigated phenotypically with regard to their ability to bind to the extracellular matrix proteins (ECM) and to produce biogenic amines. The properties have been shown to be involved in the colonization of injured tissue and invasion into host cells as well as in pharmacologic effects on humans, respectively. The CNS exhibited a low, but nevertheless clearly measurable ECM binding capacity, except for strains of Staphylococcus equorum and Staphylococcus succinus, which show a comparable or even higher binding to fibrinogen and fibronectin than that of the control strain Staphylococcus aureus Cowan. Formation of biogenic amines could be often detected in S. carnosus, S. condimenti and S. strains, but rarely in S. equorum and not in S. succinus and S. xylosus strains. Mostly, 2-phenylethylamine, tyramine and tryptamine were formed by resting cells in amounts < 25. mg/l, whereas growing cells formed high amounts (> 100. mg/l) of 2-phenylethylamine and putrescine. This study confirmed the need of consideration of ECM binding and biogenic amine formation in the safety assessment of CNS used in the production of fermented foods. © 2011 Elsevier B.V.


Toepfl S.,German Institute of Food Technologies DIL
Stewart Postharvest Review | Year: 2012

By pulsed electric field (PEF) application an energy efficient permeabilization of plant, animal and microbial cells is achieved. Since first reports in the 1960s many possible applications of the effect termed electroporation in food and bio-processing have been identified. In 2006 a first commercial installation for fruit juice preservation has been achieved in the US. Since then industrial scale processing equipment for liquid and solid products has been developed. In 2009 an industrial juice preservation line has been installed in Europe, followed by equipment for pre-treatment of vegetables in 2010. At present approximately 30 commercial units are operated worldwide. This chapter will review technical requirements and design guidelines and provide an update on the current commercial exploitation of the technique. © 2012 Stewart Postharvest Solutions (UK) Ltd.


Shayanfar S.,German Institute of Food Technologies DIL | Chauhan O.,Defense Food Research Laboratory | Toepfl S.,German Institute of Food Technologies DIL | Heinz V.,German Institute of Food Technologies DIL
International Journal of Food Science and Technology | Year: 2013

The combination of pulsed electric fields (PEF) and texturizing and antifreeze agents on quality retention of defrosted potato strips were studied. Potato strips (10 mm thickness, 100 g) were placed in different solutions (1% w/v) of CaCl2, glycerol, trehalose as well as NaCl and sucrose, treated with PEF (0.5 kV cm-1, 100 pulses, 4 Hz). Then, all the samples were soaked in the same solutions for 10 min. After draining, samples were packed into polypropylene pouches and stored at -18 °C for 12 h. Samples were thawed out at room temperature (20 °C) in 3 h. Untreated controls and PEF treated control samples were also frozen and thawed in similar conditions. To assess the potato strip quality, the thawed samples were analysed for moisture content, weight loss, firmness and colour attributes. The results indicate that PEF treatment by itself is not a suitable pre-treatment method for frozen potato strips and should be assisted by CaCl2 and trehalose treatment to prevent softening after defrosting. Firmness analyses determined that application of PEF alone results in 2.38 N. However, PEF in combination with CaCl2 and trehalose result in 2.97 N and 2.99 N, respectively, which are both significantly firmer than the samples solely treated with PEF. CaCl2 and trehalose were effective in not only maintaining the structural integrity of the cells, but also retaining colour attributes. The L* value was found to be higher (P < 0.05) in CaCl2 and trehalose treated samples (58.95 and 57.21, respectively), as compared to PEF treated samples (53.97) denoting a darker colour. Application of CaCl2 and trehalsoe in combination with PEF also resulted in significantly less weight loss after thawing. © 2013 Institute of Food Science and Technology.


Wieschebrock M.,German Institute of Food Technologies DIL | Seitter M.,German Institute of Food Technologies DIL | Hertel C.,German Institute of Food Technologies DIL
European Food Research and Technology | Year: 2011

A real-time PCR system with 16S rRNA gene-targeted group-specific primers was developed to quantitatively detect lactic acid bacteria (LAB) of the genera Lactobacillus, Leuconostoc, Pediococcus, and Weissella in different types of commercially available dried sourdoughs. Despite a high degree of degradation in the DNA isolated from the doughs, the 341-bp 16S rRNA gene fragment of the sourdough LAB biota could specifically be amplified. For dried sourdoughs, the resulting calculated LAB cell counts were determined to be up to 3.7 × 107 cells/g fresh dough, whereas in non-fermented dough acidifiers, used as a control, the calculated LAB cell counts did not exceed 3.6 × 104 cells/g fresh dough. Moreover, the effect of low pH and/or high lactic acid concentrations prevailing in the doughs on the detectability of LAB cells in spray- and roller-dried sourdoughs by PCR was investigated. Drying of non-acidified sourdoughs still permitted to detect the LAB cells by PCR, whereas drying of acidified doughs reduced the detectable cell counts by approximately 5 (spray dried) and 2 (roller dried) orders of magnitudes. Incubation of acidified doughs for 24 h did not affect the detectability of LAB cells in spray-dried doughs but further reduced the detectable cell counts in roller-dried doughs by additional 2 orders of magnitude. © 2011 Springer-Verlag.


Buckow R.,CSIRO | Ng S.,CSIRO | Toepfl S.,German Institute of Food Technologies DIL
Comprehensive Reviews in Food Science and Food Safety | Year: 2013

During the last decades pulsed electric field (PEF) processing received considerable attention due to its potential to enhance food products or create alternatives to conventional methods in food processing. It is generally acknowledged that PEF processing can deliver safe and chill-stable fruit juices with fresh-like sensory and nutritional properties. Relatively low-processing temperature and short residence times can achieve highly effective inactivation of microorganisms while retaining product quality. A first commercial application of PEF for preservation of fruit juices was launched in 2006 in the United States. Since then, industrial-scale processing equipment for liquid and solid products were developed and, in Europe in 2009, an industrial juice preservation line was installed using 20 kV/cm pulses at 40 to 50 °C to extend the chill-stability of fruit juices, including citrus juices and smoothies, from 6 to 21 d. The related PEF processing costs are in the range of US $0.02 to 0.03 per liter and are justified due to access to new markets and reduced return of spoiled product. However, despite its commercial success there are still many unknown factors associated with PEF processing of fruit and citrus juices and many conflicting reports in the literature. This literature review, therefore, aims to provide a comprehensive overview of the current scientific knowledge of PEF effects on microbial, enzymatic, nutritional, and sensory quality and stability of orange juices. © 2013 CSIRO and DIL.

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