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- Author or Editor: S. Tömösközi x
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Abstract
After wheat, rye is the second most important raw material for bread and bakery products, and it is one of the most excellent sources of dietary fibres and bioactive compounds. Besides, rye is utilised in more and more other food products as well, such as breakfast cereals, porridges, pasta, snack products, etc. Interestingly, its production is decreasing worldwide, probably because of the expansion of other cereals (e.g. triticale), but also the effect of climate change can also play a role therein. However, there is no doubt that scientific research aimed at studying the possible health benefits and the potential of rye in the development of novel food products has intensified over the past decade.
The aim of our paper is to make a comprehensive review of the latest results on the compositional and technological properties of rye that fundamentally influence its utilisation for food purposes. Furthermore, this review aims to identify the current development directions and trends of rye products.
In Australia in the early 1890s, the wheat breeder William Farrer and chemist Frederick Guthrie shared a vision of selecting cross-bred wheats for enhanced grain quality. Guthrie was the newly appointed chemist of the Department of Agriculture of the Colony of New South Wales. Their goal to select lines with good milling quality was difficult because Farrer’s plots produced only ounces of grain for testing. In a day when there was no written background to the task, Guthrie set about devising small-scale milling equipment that could produce flour from the many small samples of grain coming from Farrer’s breeding program. Guthrie used two pairs of small rolls manufactured by the Ganz Company of Budapest. The testing procedure was extremely tedious, requiring 13 successive passes of milling and sieving. Guthrie’s test mill and the results have been described in several publications. In addition, his mill has been reconstructed as a one-quarter-scale model as a result of the efforts of Mr Colin Hopkins, a retired chemical engineer. In contrast to this 120-year-old technology, there is now more advanced technology for test milling very small grain samples (only 5 to 10 grams of grain) with the development of a novel laboratory micro-mill, the FQC-2000, manufactured by Inter-Labor, Hungary. These old and new developments have involved collaborations between Hungary and Australia.
An automatic flow injection (FIA) and two possible reference gas chromatographic (liquid and headspace sampling GC) methods including appropriate sample preparation were developed and validated for determination of acetone in milk. The methods were tested by preserved raw milk samples. The FIA results were compared with data obtained by GC determinations. It was found that FIA procedure is suitable for rapid automated measurement of acetone in the range of 0-5 mmol l-1 in milk, therefore it is a promising analytical method for ketosis monitoring in dairy farms.
The authors' hypothesis is that the members of the tricarboxylic acid cycle (TCA cycle) such as citrate decrease in association with increased ketone body formation. To prove this hypothesis the connection between ketone bodies and citrate formation of milk was studied. A fluorimetric method was used to determine citrate and a headspace sampling gas chromatographic (GC) method was developed for determination of ketone bodies. Under real conditions of milk sampling, transport and storage, preserved milk samples of 119 clinically healthy dairy cows obtained in the 48 hours after milking were investigated. A low level of acetoacetate (ACAC) was found in all samples. This fact can be explained by the spontaneous decarboxylation of acetoacetate during sample storage (previously decarboxylised acetoacetate = pdACAC) and, consequently, the majority of the amount of acetoacetate in the samples (AC+pdACAC) appeared in the measured acetone concentrations. Based on the measured acetone concentration of milk samples two groups were formed retrospectively: HA (high-acetone) group (n = 41) with an AC+pdACAC concentration of ≯ 0.4 mmol/l and a LA (low-acetone) group (n = 78) with an AC+pdACAC level of ≤ 0.4 mmol/l. In the milk of cows of Group HA a positive correlation (r = +0.623) and linear connection between acetone (AC+pdACAC) and β-hydroxybutyrate (BOHB) levels was found [BOHB = 2.491 + 0.586 × (pdAC + ACAC)]. Furthermore, in this group a negative correlation between citrate and BOHB and AC+pdACAC was also established (r = -0.579). Focusing on the results of this group the authors found a significant drop of AC+pdACAC and citrate during the metabolically critical first 1-4 weeks of lactation. For this reason they suggest that simple, easy, automated methods (i.e. flow injection analysis, Fourier transformation infrared analysis) should be introduced for the simultaneous determination of acetone and citrate concentration in milk to make the evaluation of the energy status of high-producing dairy cows easier and more certain.
Abstract
Proper gluten quantitation is essential for providing safe gluten-free food for patients living with celiac disease (CD). However, gluten quantitation faces several challenges: the lack of a reference method and certified reference materials, the variability of methods and the effects of genetic and environmental factors on gluten. Among all these challenges our research group focuses on gluten reference material development. Gluten content is determined by enzyme linked immunosorbent assay (ELISA) methods to obtain comparable data for the selection of cultivars used in our reference material development efforts. As ELISA methods are developed for determining low gluten concentrations, application for these special research purposes requires a 10,000-fold dilution. The formerly performed process was a post-extraction liquid dilution that proved to be sufficient for wheat samples. However, gluten contents of rye and barley samples were found to be overestimated by ELISA methods. One of the suggested reasons is the structural and solubility changes of gluten proteins during the dilution process. Therefore, our present study focuses on the comparison of the original dilution method and a revised version using solid-phase dilution in a gluten-free matrix.
Role of rice and added wheat protein in the mixing properties of different rice flours
(A preliminary study)
Structure and composition of wheat storage proteins and functional properties of wheat gluten are well studied; therefore several methods and instruments are available to determine these properties. The investigation of functional properties of rice proteins, depending on the different goal of utilisation, has not been well established, yet. In this study, the rheological properties of four varieties of rice flour were studied using a 50 g Farinograph demonstrating the mixing properties of rice flours and the alterations of these properties caused by the supplementation of wheat proteins. The considerable differences identified on the mixing curves of different rice flours indicate that the investigation of mixing properties can be one of the useful approaches for the characterisation of functional properties of rice dough. The large effects of the addition of wheat gluten on the mixing properties of rice flours demonstrate the possibility of using rice flour and dough as a wheat protein free model system for the in vitro investigation of the functional roles of wheat storage proteins.
Traditionally, triticale is mainly used as animal feed, the use for human utilization is still uncertain. However, in the past few decades, importance of triticale is increasing globally. Therefore, the determination of nutritionally important parameters of triticale and study of their genetic and environmental (G×E) variability have essential importance. In this study, ten hexaploid triticales along with reference wheat and rye varieties were grown at two locations in Hungary in a three-year-long experiment. Crude protein (8.6–16.3%), crude fat (0.86–1.98%), starch (57.6–65.0%), and dietary fibre values (7.5–13.7%) showed notable differences, significant genotype control were detected in all tested parameters except ash content (1.42–2.10%). The analysis of variance confirmed that crop year affected all traits, and also location had significant effect on the formation of protein and – to a lesser extent – the fibre levels. Furthermore, interactions between the effects were observed. Generally, nutritional characteristics of triticales were positioned between wheat and rye in this experiment; however, there were notable differences between the genotypes, and also the magnitudes of environmental effects were significant. Nutritional values of triticale provide a prospect for food production and human consumption.
Disorders induced by cereal proteins (e.g. wheat allergy, celiac disease) are widespread in human population. Since their only effective treatment is the avoidance of the problematic proteins, patients have to be familiar with the composition of food products. For checking special foods produced for them, proper analytical methods are necessary. At the moment, in gluten analysis there are no reference methods and reference materials which model real food matrices. During the production and experimental utilisation of our previously developed reference material candidate, numerous questions emerged. As our model product is a real food matrix, interactions can be present between gluten proteins and other macro and micro components. Fat content of the baked cookies is almost 20%, which might affect the results of ELISA measurements. The detectable gluten content is significantly increasing after the defatting procedure, as a pre-treatment of samples. Moreover, baking is a common food processing step that might modify the structure of gluten proteins leading to denaturation and aggregation. In the soluble protein fraction the amount of low molecular weight proteins increases, while that of high molecular weight proteins decreases during the baking procedure.
Quantitation of gluten in gluten-free products is a great challenge as it is hindered by several factors including the lack of certified reference materials. To resolve this problem, our research group, in cooperation with other international experts, started a series of experiments with the goal of the production of a suitable gluten reference material. As a part of this research, several different wheat cultivars and their isolated gluten proteins were characterized by different methods, including enzyme-linked immunosorbent assay (ELISA). However, we need to know the performance of the ELISA methods used for this special area of research. During the present work we investigated the accuracy and precision of two different ELISA methods for our own laboratory conditions and special sample matrices (wheat flours and gliadin isolate). We have found that the tested performance characteristics of the methods seem to be appropriate on a case-by-case basis, but the long-term measurement uncertainty is higher, which makes it difficult to evaluate the results obtained with the ELISA method for these types of samples.
Comparative study of composition and technological quality of amaranth
I. Gross chemical composition, amino acid and mineral content
Eight groups of amaranth grain samples, belonging to the species Amaranthus cruentus and A. hypochondriacus , grown in Austria and Hungary were studied. Gross chemical composition, amino acid content and mineral composition of the whole grain were determined. The effect of heat treatment on amino acid content was also investigated. The range of concentration of main constituents of samples studied corresponded to the average data reported by other researchers. However, the relatively big difference between lowest (14.23%) and highest (17.40%) protein content suggests that genetic potential for increasing the protein content may be realized in breeding. Amino acid composition profile is generally closer to Leguminosae than to cereal grains except for sulphur containing amino acids being present in higher amount in amaranth than in legumes. The concentrations of minerals in seeds varied in a relatively wide range, and the micro-components, like Fe, Cu, Zn, were present in higher amount in amaranth seeds compared to the average values found in wheat. It was confirmed that heat treatment of amaranth grain (e.g. popping) might reduce the available lysine content. Contradictory data published in the literature may be explained by differences in initial sugar and moisture content of grain, which influence the rate of potential Maillard-reaction.
