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- Author or Editor: É. Gelencsér x
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Earlier studies on protein antinutrients and allergens naturally present in legume seeds have shown that these compounds are responsible for the impaired performance of experimental animals when exposed for a long term. These reactions were characterized by lowered nutritional performance, reduced growth, pure digestion and absorption, changes in gut motility, structural damage in small intestine and diarrhoea. A lot of efforts were made for gathering data on heat stability and resistance to chemical or enzyme treatments of these compounds to reduce or eliminate these harmful effects.A novel research approach has described that these compounds have a special regulatory role in the gut metabolism and modulate hormone and immune responses which resulted in a novel concept of “nonnutritive biologically active compound”. These studies revealed that the chemical structure of these compounds was responsible for the induction of such physiological reactions as increased endogen N-loss, change in the plasma amino acid concentration or plasma lipid composition with reduction of total cholesterol level or developing of harmful immune responses to luminal antigens resistant to the gut digestion. Resent studies were therefore related to the description of their interaction with the gut metabolism and understanding of the modulation of gut immune responses to luminal antigens.This review was inspired to summarise the research efforts on the above field performed by the Nutritional and Biological Units of the Central Food Research Institute.
It is well established that the ingestion of cereal prolamins, such as gluten, causes the characteristic symptoms of celiac disease (CD) in people predisposed to it. DNA-based PCR method provides new ways to detect gluten in processed foodstuffs, such as bread. The aim of this work was to adapt a new primer pair combination and to initiate a carefully elaborated PCR methodology to experiment with DNA-based analysis. At first, the purity of cleaned DNA was verified using B49317 and A49855 chloroplast DNA primer pair. Then TR01/2 wheat specific PCR primer pair was used for checking the origin of the DNA, and P1/2 microsatellite (SSR) adapted primer pair for detecting allergen (gluten) specific residues. Method optimisation was achieved with cereal flour samples, then bread and dry pasta products from wheat were used, which were analysed as heat-treated samples with three primer pairs. The gluten specific primer pair was tested on cross-reactive cereals such as rye, barley, triticale and on some questionable cereals, such as oat, and pseudo-cereals, e.g. buck wheat and amaranth.
The aim of the study was to assay by PCR screening method whether the processing and the thermal stress have any influence on the feasibility of the detection of genetically modified DNA in different kinds of processed meat products such as sausages, liver cans, ready-to-eat hamburgers. The model meat products have been prepared with soybean meal spiked with RR (Roundup Ready) soybean meal in 0.5%, 1%, 1.5% and 2%. The samples were prepared under industrial circumstances. The assay was based on the detection of the specific part of the 35S promoter and the NOS terminator sequences. The modified PCR method was shown to be suitable for screening of GMOs in raw and also in moderately and highly processed meat samples when extreme heat treatment and pressure were used for the preparation of meat products. Half a percent RR soy contamination could be detected even if the food products underwent high temperature treatment.
The main goal of our work was to develop a rapid, simple, and economical DNA extraction method for food (especially for meat products) analysis. This extraction and purification procedure was based on the three-phase partitioning (TPP) method. The developed new DNA-TPP method and Wizard DNA Clean-Up System (Promega, USA) have been compared concerning extraction efficiency, purity and DNA suitability for amplification. The quality and quantity of the purified DNA solutions were controlled by spectrophotometer and the amplification efficiency by simple qualitative PCR. All of prepared DNA solutions were pure enough for the PCR and contained appropriate quantity of DNA. Thus, 118 bp length amplicons could have been obtained by the specific lectin-gene PCR in all cases. This method proved to be an alternative one to isolate DNA from meat samples simply and economically.
A novel step in bean (Phaseolus vulgaris) α-amylase inhibitor (AAI) purification, based on the application of an inorganic adsorbent, zinc hydroxide, was developed. The new method was substantially faster than existing protocols. Up to 98% of bean seed proteins were bound to the white precipitate in the range of 1–4% (w/v) zinc hydroxide, while the amount of bound bean AAI was far less in the range of 1–2%. The AAI-enriched fraction, unbound by zinc hydroxide, was further purified by DEAE-(diethylaminoethyl)chromatography and gel filtration. It was found that zinc hydroxide binds the majority of soluble proteins of bean, while it leaves α-amylase inhibitor in solution. The binding of proteins to zinc-hydroxide occurs in a short time and the change caused in the buffer composition is insignificant, thus it may open new approaches in purification of other proteins, too.
Reliable determination of microbial or transgenic Cry toxins is an essential issue in food and feed analyses, and enzyme-linked immunosorbent assays (ELISAs) are the method of choice for quantifying these toxins currently in food and environmental analysis. Internal Quality Control (IQC) is an indispensable method to assess accuracy, precision, and reproducibility of analytical measurements. To assess the utility of the ELISA method, IQC was performed on EnviroLogix Cry1Ab/Cry1Ac QualiPlate ELISA with manufacturer supplied analytical standards. Applicability of negative and positive controls (C− and C+) was examined by Shewhart Control Charts for bias and Control Chart of the Range of Duplicates for precision. Linear regression (up to 5 ng ml−1 Cry1Ab concentration) of the commercial ELISA kit was compared to sigmoid calibration (up to 60 ng ml−1 Cry1Ab concentration). For immunoassay optimization process, possible matrix effects in different liquid and solid vertebrate tissues were examined by determination of the limit of detection values in these matrices.
Yellow pea flour contains very low quantity of prolamins, thus it could be a good alternative dietary source for individuals suffering from celiac disease or wheat allergy. Beside emulsifiers, enzymes can be used for developing noodle structure with high quality. Transglutaminase (TG) enzyme was tested in model systems for improving noodle structure by using beneficial cross-linking property of the enzyme. Sensory-and cooking properties and biochemical attributes of proteins were evaluated to characterize structure-function relationships in accordance with the concentration of the applied enzyme. The amount of water and salt soluble protein fractions was reduced meaningfully and the molecular weight distributions assessed by SDS PAGE were changed by addition of 50–200 mg kg −1 TG enzyme. At the same time, sensory properties were improved and high water uptake and low cooking loss were also observed. Forasmuch an increase has been expected in the amount of the cross-linked molecules, the cross-reactivity of prolamins with anti-gliadin antibody was also tested to reduce the risk related to gluten sensitivity. Finally, the possible contamination with wheat was controlled by DNA-based PCR.
The expression levels of two marker proteins (phosphinotrichin acetyltransferase, PAT and wheat germ agglutinin, WGA) in the transgenic wheat lines and their resistance to digestion in small intestine of rats were studied in comparison with their non-transgenic counterpart obtained from green house and field experiments of two subsequent years. The marker proteins were quantified by ELISA. It was found that the expression of PAT and WGA markedly increased when the wheat was grown in the field compared to that in the greenhouse. There were no significant differences between the WGA contents of the parent and transgenic wheat lines, but a broad range of expression of PAT and WGA was observed in the transgenic lines. PAT did not survive in the small intestine of the rats, while WGA was resistant to digestion in different ratios and was bound to the intestinal epithelium.
