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Bruhl L.,Max Rubner Institute | Weisshaar R.,Chemisches und Veterinaruntersuchungsamt CVUA Stuttgart | Matthaus B.,Max Rubner Institute
European Journal of Lipid Science and Technology | Year: 2016

The occurrence of monoepoxy fatty acids in used frying oils and in other common foods has been determined. Monoepoxy fatty acids with trans-9,10- and cis-9,10-epoxystearate and trans-12,13-, trans-9,10-, cis-12,13- and cis- 9,10-epoxyoctadecenoate were found at average levels of 3.7g/kg in used frying fats and oils, but also at about 2g/kg in the fat fraction of chocolate. They were also detected in pumpkin seed, sweet almond, groundnut, sunflower, and olive oils at average levels of 3.4, 1.7, 1.4, 1.0, and 0.2g/kg, respectively. Their formation during heating at 175°C was observed for sunflower, rapeseed, soybean, and linseed oil and compared with the increase of polar compounds and polymerized triacylglycerols as other important quality indicators for frying oils. During heating for 16h, the level of monoepoxy fatty acids increased to about 30, 18, 8, and 4g/kg for olive, sunflower, linseed, and rapeseed oils, respectively. The influence of the heating temperature was surveyed for refined soybean oil at 160, 170, 180, and 200°C. Heating of two sets of five different refined and virgin rapeseed oils revealed a significant lower formation of monoepoxy fatty acids for refined oils at a median level of 4.6g/kg compared to7.7g/kg for virgin oils. Practical applications: Determination of fatty acid methyl esters is one of the most common analyses for the evaluation of oils and fats. The assessment of the monoepoxy fatty acids as part of these analyses can provide a first indication about used frying fats and oils, which reached the end of their applicability. The formation of monoepoxy fatty acids is affected by the fatty acid composition of the oil, the heating temperature, and the production of the oil. Therefore, frying oils may contain varying amounts of monoepoxy fatty acids at the maximum limit for polar compounds and polymerized triacylglycerols as used in the official food control. However, all used frying oils investigated by the official food control showing more than 7g/kg of monoepoxy fatty acids had to be rejected due to the limits exceeded for polar compounds and polymerized triacylglycerols. Therefore, this limit of 7g/kg monoepoxy fatty acids level is proposed as a level for screening the usability of used frying fats and oils. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Weisshaar R.,Chemisches und Veterinaruntersuchungsamt CVUA Stuttgart
European Journal of Lipid Science and Technology | Year: 2014

Quality of deep-fried food is inseparably attached to the quality of the used deep-frying oil. Taste, flavor, shelf life, consumer acceptance, and safety of fried food essentially depend on frying oil quality. Evaluation of frying oil quality therefore is an important issue for both frying operators and official food control agencies. Organoleptic evaluation is an essential step in the monitoring of frying fat quality. Several official laboratory methods are available to support the sensory evaluation. Total polar materials (TPM) and polymer TAGs (PTG) are the most reliable parameters for this purpose. Recommended and widely accepted limits are 24% for TPM and 12% for PTG. When oxidative alterations strongly predominate over thermal alterations, sensory defects can appear before TPM and PTG reach recommended values. In that case additional parameters like anisidine value, carbonyl value, or epoxy fatty acids should be considered. A number of physical and chemical rapid methods are available. Despite the limited informative value and the possibility of error of rapid tests, they are essential for fryer operators, because they deliver information about fat quality in real-time. Most reliable for most applications are quick tests measuring TPM. A unique and powerful tool for the simultaneous detection of multiple parameters corresponding to thermal and oxidative alterations is near infrared spectroscopy (NIRS), which will become more and more important in future. Evaluation of used frying oils is a complex issue due to the endless number of possible alterations, depending on frying conditions, nature of frying oil, and nature of fried food. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Kobler H.,Chemisches und Veterinaruntersuchungsamt CVUA Stuttgart | Monakhova Y.B.,Chemisches und Veterinaruntersuchungsamt CVUA Karlsruhe | Monakhova Y.B.,Chernyshevsky Saratov State University | Kuballa T.,Chemisches und Veterinaruntersuchungsamt CVUA Karlsruhe | And 5 more authors.
Journal of Agricultural and Food Chemistry | Year: 2011

Nontargeted 400 MHz 13C and 1H nuclear magnetic resonance (NMR) spectroscopy was used in the context of food surveillance to reveal Pinus species whose nuts cause taste disturbance following their consumption, the so-called pine nut syndrome (PNS). Using principal component analysis, three groups of pine nuts were distinguished. PNS-causing products were found in only one of the groups, which however also included some normal products. Sensory analysis was still required to confirm PNS, but NMR allowed the sorting of 53% of 57 samples, which belong to the two groups not containing PNS species. Furthermore, soft independent modeling of class analogy was able to classify the samples between the three groups. NMR spectroscopy was judged as suitable for the screening of pine nuts for PNS. This process may be advantageous as a means of importation control that will allow the identification of samples suitable for direct clearance and those that require further sensory analysis. © 2011 American Chemical Society. Source


Contzen M.,Chemisches und Veterinaruntersuchungsamt CVUA Stuttgart | Hailer M.,Chemisches und Veterinaruntersuchungsamt CVUA Stuttgart | Rau J.,Chemisches und Veterinaruntersuchungsamt CVUA Stuttgart
International Journal of Food Microbiology | Year: 2014

Bacillus (B.) cytotoxicus is a newly described thermotolerant member of the Bacillus cereus group. This potential foodborne pathogen had so far only been isolated from vegetable products, including mashed potatoes. Here we report the detection of B. cytotoxicus in a variety of potato products taken on retail level or from catering establishments (n. = 151). Identification of isolates as B. cytotoxicus was performed after enrichment at 50. °C, followed by differentiation using Fourier transform-infrared spectroscopy and detection of the specific cytK-1 gene by PCR.Thirty-five percent of all samples were positive for B. cytotoxicus. Highest prevalence was found in dehydrated potato products (44/62. = 71%) such as powder for mashed potatoes and products made thereof. B. cytotoxicus was not detected in products that were evidently made directly from potatoes (n. = 24) but in one sample of raw potatoes (n. = 10; 10%).The high prevalence of this thermotolerant pathogen in potato products could pose a risk for consumers, especially if prepared foods are held at improper holding temperatures. © 2014 Elsevier B.V. Source

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