Jasna Mastilović

Near Infrared Spectroscopy—Advanced Analytical Tool in Wheat Breeding, Trade, and Processing

Due to its suitability to be processed in wide range of final products, wheat has an upmost significance among all cereals. The global wheat marketing are becoming increasingly demanding with regard to all aspects of wheat quality. To fulfil these demands, each link in wheat production chain—breeding, trade, and processing should be supported by objective and reliable quality assessment tool such as the near infrared spectroscopy (NIRS) technique. The aim of this paper is to summarize the recent advances in the applications of NIRS technique for wheat quality control applicable in wheat breeding, trade, and processing. Although heavily intertwined, each link is characterized by specific NIRS applications, with ultimate aim—the production of consumer-appealing and safe final products.

The Application of Near Infrared Spectroscopy in Wheat Quality Control

The application of near infrared spectroscopic technique for the quantitative analysis of food products and commodities is nowadays widely accepted. However, 160 years passed from the discover of near infrared part of the spectrum to its first analytical application which is related to the work of Karl Norris who firstly demonstrated the potential of the NIRS in quantitative analysis particularly for prediction of moisture and protein content in wheat. The intense development of this technique during the last 50 years has been challenged by the development of powerful computers, softwares and chemometric tools, since the NIRS data processing is quite demanding task. The near infrared spectroscopy is an instrumental technique based on measuring the intensity of reflectance or intensity of transmission of radiation from the near infrared region of the electromagnetic spectrum (800-2500 nm) by the test sample. The intensity of the reflection and transmission depends on the rate of absorption of radiation by the sample, which leads to excitation of hydrogen bonds (CH, NH, OH). As the tested samples are very complex in composition, it happens that on the same wavelength, several organic bonds involving hydrogen vibrate producing overlapped spectral bands. Therefore, the resulting NIR spectrum looks like a slightly wavy line with no clearly defined features, with very broad and overlapped molecular overtone and combination bands, which complicate to assign them to specific chemical constituent and make impossible to determine the direct relationship between the concentration of ingredients of interest and the absorbed radiation energy (Fig. 1).

Alternaria toxins in wheat from the Autonomous Province of Vojvodina, Serbia: a preliminary survey

Although Fusarium species remain a main source of mycotoxin contamination of wheat, in recent years, due to the evident climatic changes, other mycotoxigenic fungi have been recognised as important wheat contaminants. Alternaria species, especially A. alternata, have been found as contaminants of wheat as well as wheat-based products. Under favourable conditions A. alternata very often produce alternariol (AOH), alternariol monomethyl ether (AME), tenuazonic acid (TeA) and others Alternaria toxins. The aim of the present study was to examine the presence of three Alternaria toxins (AOH, AME and TeA) in wheat samples harvested during three years (2011–13). To this end, 92 samples were collected during wheat harvesting from different growing regions of the Autonomous Province of Vojvodina, which represents the most important wheat-growing area in Serbia. The presence of Alternaria toxins was analysed by HPLC with electrospray ionisation triple quadrupole mass spectrometry (LC-ESI-MS/MS). Among all the analysed wheat samples, 63 (68.5%) were contaminated with TeA, 11 (12.0%) with AOH and 6 (6.5%) with AME. Furthermore, the maximum and mean toxin concentrations were 2676 and 92.4 µg kg−1, 48.9 and 18.6 µg kg−1, and 70.2 and 39.0 µg kg−1 for TeA, AOH and AME, respectively. Co-occurrence of three Alternaria toxins in wheat samples was detected in six samples; a combination of two toxins was found in two samples; and 64 samples contained one toxin. The results showed that among 92 analysed wheat samples, only 20 (21.7%) samples were without Alternaria toxins. The presence of Alternaria toxins was also investigated in terms of weather conditions recorded during the period of investigation, as well as with the sampling region. This study represents the first preliminary report of the natural occurrence of Alternaria toxins in wheat (Triticum aestivum) from Serbia.

Effect of Different Ripening Conditions on Pigments of Pepper for Paprika Production at Green Stage of Maturity

The content and composition of pigments and CIELab color properties in fruits ripened in the field were compared with those obtained in ground paprika produced from green pepper fruits after postharvest ripening for 15 days in a greenhouse under different conditions. Obtained data for pigment content, composition, and esterification rate have shown that the processes of pigment biosynthesis in fruits ripened under greenhouse conditions are different from those occurring in fruits naturally matured in the field: the red/yellow pigment ratio (3:1) in greenhouse-ripened fruits is much higher than in naturally ripened pepper in breaker (1:1) and also in faint red (2:1) ripening stages from the field. Additionally, during the postharvest ripening of green pepper in the greenhouse esterification processes are less expressed than during the ripening of the fruits in the field. Postharvest ripening under natural daylight resulted in higher content of red pigments, followed by higher ASTA value.

Robustness of the near infrared spectroscopy method determined using univariate and multivariate approach.

The robustness assessment is a part of a method validation protocol, during which several characteristics of an analytical method are also evaluated (e.g. accuracy, repeatability, reproducibility, linearity, intermediate precision, measurement uncertainty) in order to assess its fitness for purpose. The purpose of robustness assessment of the near infrared spectroscopy method (NIRS) is to indicate which factor significantly influence the obtained results, as well as to point to the potential problems that might occur in the routine application of the method. The assessment of robustness of the NIRS method included variation of certain operational and environmental factors at three level (-1,0,1) by applying univariate (one-variable-at-a-time, OVAT) and multivariate (multivariate-at-a-time, MVAT) approach to the experimental design. Operational and environmental factors that were varied included the number of subsamples to be measured in the NIRS measurement (1), environmental temperature (2), sample temperature (3), environmental air humidity (4), instrument voltage (5) and lamp aging (6). Regardless the applied experimental design, external factors with significant influence on obtained NIRS results were indicated, as well as pointed the potential problems that might occur in the routine application of the method. In order to avoid them, every effort should be made to stabilize instrument and sample temperature and to standardize the homogeneity and number of subsamples to be measured in NIRS measurement. Moreover, the obtained results highlighted the necessity that the NIRS instruments should work through a voltage regulator.

Possibility of Alternaria toxins reduction by extrusion processing of whole wheat flour.

This study represents the first report about possibility of reduction of Alternaria toxins in wheat using the extrusion process. Effects of extrusion processing parameters - moisture content (w=16, 20, 24g/100g), feeding rate (q=15, 20, 25kg/h), and screw speed (v=300, 390, 480rpm), on reduction rate of tenuazonic acid (TeA), alternariol (AOH) and alternariol monomethyl ether (AME), in whole wheat flour were investigated. Temperature ranged between 111.1 and 160.8°C, while the absolute pressure was from 0.17 to 0.23MPa. The simultaneous influence of w and v was the most important for TeA reduction (p<0.05), while v and q were the most influential for AOH reduction (p<0.01). Level of AME reduction was mostly influenced by w and v (p<0.10). Optimal parameters for reduction of all three Alternaria toxins were as follows: w=24g/100g, q=25kg/h, v=390rpm, with a reduction of 65.6% for TeA, 87.9% for AOH and 94.5% for AME.

Development of low calorie jams with increased content of natural dietary fibre made from tomato pomace

In this study, four jam formulations were developed, starting with the basic formulation (Jam 1) containing sucrose and without added pectin. Sucrose was partially (50%) replaced by stevioside in formulations of Jam 2 and 3, while in Jam 4 sucrose was completely replaced by fructose and stevioside, making this formulation suitable for diabetic patients. Jam formulations 1 and 2, prepared without added pectin, were thermally stable in the temperature range of 25-90°C, which indicate their potential use as fruit fillings. Jam formulations 3 and 4 were assessed by the sensory panel as more spreadable since tomato pomace particles are incorporated in pectin network which acts as a lubricant. Jam formulations were characterized by a lower total carbohydrate content (17.23-43.81%) and lower energy value (87.1-193.7kcal/100g) when compared to commercial products. Tomato pomace jams contained 15-20 times more dietary fibre than commercial apricot jam.

Change of surface colour parameters during storage of paprika (Capsicum annuum L.)

The change of paprika surface colour during three years of storage was monitored by measuring CIEL*a*b* colour parameters once a year. Ten commercial and three branded paprika samples, originating from Hungary, Austria and Serbia, were stored in original packaging at ambient temperature in dark during the storage period. The colour of paprika powder was measured by Chroma Meter CR-400 (Konica Minolta, Japan), using attachment for granular materials CR-A50. Directly measured colour parameters were CIE L* (lightness), a* (+a* = redness, -a* = greenness), b* (+b* = yellowness, -b* = blueness) and dominant wavelength (DWL), while derived colour parameters were chroma (C*), hue angle (h°), and total colour change (ΔE). Paprika samples had similar granulation, and therefore it was concluded that it did not influence the colour reflection. The change of reflected colour of paprika powder during storage can be characterized by increase of CIE L* and b* colour values and decrease of a* colour value. Therefore, chroma values remained almost unchanged, while hue angle showed shift in spectrum from red-orange to orange-yellow, similarly to dominant wavelength. The paprika samples changed their colour most rapidly during the first year of storage, except the branded paprika from Serbia. Commercial paprika samples from Serbian market changed their colour more rapidly comparing to other investigated samples.

Alveograph and Bread Making Quality of Wheat Dough as Affected by Added Glucose Oxidase

Although there is considerable interest in glucose oxidase, little is known about its activity on rheological characteristics of wheat dough and with bread making quality. Influence that the glucose oxidase exerts on rheological properties of the wheat dough is investigated on the basic of rheological determinations obtained with alveograph. Influence of glucose oxidase on bread making properties is determined on the basic of result obtained from the laboratory scale baking tests. In order to clearly establish relations between added dose of glucose oxidase (0.002; 0.004; 0.006 %) and rheological properties of wheat dough, as well as with bread making quality, analysis of dough with and without glucose oxidase (control sample) is performed and results are discussed with comparison with L-ascorbic acid as the most commonly used oxidative improver. Results show that glucose oxidase cause greatest increase of dough tenacity and causal reduction of extensibility. This leads to a negative effect on specific volume. Glucose oxidase cause increase of crumb hardness in smaller extent than L-ascorbic acid.

A Comparative Study of Two Analytical Methods for Fat Content Determination in Brewer's Grits

The fat content of brewers grits is an important determinant of product grade and suitability for beer production, even though the content is relatively low, ranging from 0.5 to 1.5%. Fat content >1% is often considered undesirable due to its possible impact on beer quality. Traditional chemical analyses for determination of fat content cannot be applied practically to process control because they are too time-consuming. The implementation of a rapid and simple near-infrared spectroscopy (NIRS) method depends heavily on its reliability and accuracy in relation to the approved method. This study was conducted to investigate the extent of the differences between values obtained using reference and NIRS methods for determination of fat content in brewers grits. Conventional statistical evaluation, as well as extensive statistical analyses that included descriptive statistics, multivariate analysis of variance, discriminant analysis, analysis of variance, and profile analysis, were applied. Significant differences between methods were not observed. Better precision and similar accuracy compared with the reference method showed that the NIRS method could be used for process analysis with a high level of reliability.