Milica Pojić

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.

Characterization of Byproducts Originating from Hemp Oil Processing

Valorization of hemp seed meal, a byproduct of hemp oil processing, was performed by measuring the distribution of nutritional and antinutritional compounds in different hemp seed meal fractions. According to chemical composition, two cotyledon-containing fractions (>180 and <180 μm) were significantly richer in protein (p < 0.05) (41.2% ± 0.04% and 44.4% ± 0.02%, respectively), lipid (15.1% ± 0.02% and 18.6% ± 0.04%, respectively), and sugar content (4.96% ± 0.11% and 3.46% ± 0.08%, respectively) in comparison to the hull-containing fractions (>350 and >250 μm), which were significantly richer in crude fiber content (29.5% ± 0.04% and 21.3% ± 0.03%, respectively). The free radical scavenging capacity (IC50) of fraction extracts increased (p < 0.05) with increasing mean particle size (from 17.18 ± 0.59 to 5.29 ± 0.30 mg/mL). Cannabisin B and N-trans-caffeoyltyramine were the most abundant phenolic compounds in the hull fractions (from 267 ± 15.9 to 287 ± 23.1 mg/kg), while cotyledon fractions had higher content of catechin (from 313 ± 12.4 to 744 ± 22.2 mg/kg) and p-hydroxybenzoic acid (from 124 ± 6.47 to 129 ± 8.56 mg/kg (P < 0.05). Well-balanced ω-6 to ω-3 fatty acid ratio (3:1) was determined in all fractions. Antinutrients (trypsin inhibitors, phytic acid, glucosinolates, and condensed tannins) were mostly located in the cotyledon fractions. These findings indicate that the separation of hemp seed meal into different fractions could be used to concentrate valuable target compounds and consequently facilitate their recovery.

The Role of Empirical Rheology in Flour Quality Control

Rheology, as a branch of physics, studies the deformation and flow of matter in response to an applied stress or strain. According to the materials’ behaviour, they can be classified as Newtonian or non-Newtonian (Steffe, 1996; Schramm, 2004). The most of the foodstuffs exhibit properties of non-Newtonian viscoelastic systems (Abang Zaidel et al., 2010). Among them, the dough can be considered as the most unique system from the point of material science. It is viscoelastic system which exhibits shear-thinning and thixotropic behaviour (Weipert, 1990). This behaviour is the consequence of dough complex structure in which starch granules (75-80%) are surrounded by three-dimensional protein (20-25%) network (Bloksma, 1990, as cited in Weipert, 2006). Wheat proteins are consisted of gluten proteins (80-85% of total wheat protein) which comprise of prolamins (in wheat gliadins) and glutelins (in wheat glutenins) and non gluten proteins (15-20% of the total wheat proteins) such as albumins and globulins (Veraverbeke & Delcour, 2002). Gluten complex is a viscoelastic protein responsible for dough structure formation. Among the cereal technologists, rheology is widely recognized as a valuable tool in quality assessment of flour. Hence, in the cereal scientific community, rheological measurements are generally employed throughout the whole processing chain in order to monitor the mechanical properties, molecular structure and composition of the material, to imitate materials’ behaviour during processing and to anticipate the quality of the final product (Dobraszczyk & Morgenstern, 2003). Rheology is particularly important technique in revealing the influence of flour constituents and additives on dough behaviour during breadmaking. There are many test methods available to measure rheological properties, which are commonly divided into empirical (descriptive, imitative) and fundamental (basic) (Scott Blair, 1958 as cited in Weipert, 1990). Although being criticized due to their shortcomings concerning inflexibility in defining the level of deforming force, usage of strong deformation forces, interpretation of results in relative non-SI units, large sample requirements and its impossibility to define rheological parameters such as stress, strain, modulus or viscosity (Weipert, 1990; Dobraszczyk & Morgenstern, 2003), empirical rheological measurements are still indispensable in the cereal quality laboratories. According to the empirical rheological parameters it is possible to determine the optimal flour quality for a particular purpose. The empirical techniques used for dough quality

Classification and target compounds

Abstract Unsurprisingly, food production leads to the generation of many co-/by-products and waste material along the chain from collection through to various stages of processing and final manufacture. Such cogenerated products can pose environmental and economic problems thus reducing the profitability of the food industry. However, within the problem lies the solution, as these coproducts are rich in a variety of biomolecules of high relevance to the food and nonfood (e.g. pharmaceutical, cosmetic) industries and can command high value for the agro-food industry. In this chapter an overview is presented of some of the high added-value biomolecules identified in the different by-products generated by the most important industries (cereals, roots, tubers, pulses and oil crops, fruits, vegetables, meat, fish, and milk); the corresponding target compounds in each case as well as their potential applications in key sectors such as food, pharmaceutical, or biomedical are also outlined. The reader is guided to a number of relevant published articles for more in-depth descriptions, which are beyond the scope of this chapter.

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).

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.

Gelatinization properties of wheat flour as determined by empirical and fundamental rheometric method

Certain empirical rheological methods are in extensive use in wheat and/or flour research to assess starch gelatinization and pasting behavior primarily due to easy performance and good correlation with final product quality. However, their applications are often associated with specific drawbacks that could be limiting factors for certain applications, such as poor definition of the measured parameters, time-consuming nature, difficulties in interpretation of results, large sample sizes, etc. The listed shortcomings can be overcome by application of fundamental rheological methods that are based on well-defined rheological parameters such as stress, strain, viscosity and modulus. The objective of this study was to optimize the fundamental rheological method for determination of the gelatinization properties of wheat flour that correspondents to the standard widely accepted empirical rheological method—Amylograph method and to compare them in order to determine whether they can be interchangeable depending on different analytical needs. The obtained results have shown that the application of fundamental rheometric procedure for determination of pasting properties of wheat flour provides reliable determination of the gelatinization properties of wheat flour. Moreover, substantial advantages of fundamental rheometric method over the empirical one were identified including smaller sample size, ability to set the desirable heating and shear rate, shorter test duration and better precision.

Determination of free sulphydryl groups in wheat gluten under the influence of different time and temperature of incubation: Method validation

The aim of the present study was to determine the characteristics of an analytical method for determination of free sulphydryl (SH) groups of wheat gluten performed with previous gluten incubation for variable times (45, 90 and 135min) at variable temperatures (30 and 37°C), in order to determine its fitness-for-purpose. It was observed that the increase in temperature and gluten incubation time caused the increase in the amount of free SH groups, with more dynamic changes at 37°C. The method characteristics identified as relevant were: linearity, limit of detection, limit of quantification, precision (repeatability and reproducibility) and measurement uncertainty, which were checked within the validation protocol, while the method performance was monitored by X- and R-control charts. Identified method characteristics demonstrated its acceptable fitness-for-purpose, when assay included previous gluten incubation at 30°C. Although the method repeatability at 37°C was acceptable, the corresponding reproducibility did not meet the performance criterion on the basis of HORRAT value (HORRAT<2).

Content of free amino groups during postharvest wheat and flour maturation in relation to gluten quality

The objective of this study was to monitor the changes in the content of free amino groups during postharvest wheat and flour maturation. The content of free amino groups of wheat flour was analysed immediately after wheat harvest, after 50 days of wheat storage and after 14 days of flour storage varying by wet gluten samples incubation temperatures and incubation times (0, 90 or 135 min at 30°C and after that 180 min at 37°C). The results were observed in relation to wheat-bug damaged kernels content, gluten index values, proteolytic activity and electrophoretic properties of gliadins and glutenins. The content of free amino groups increased during postharvest wheat and flour maturation periods. Proteolytic activity values were the highest 50 days after the wheat storage. The electrophoretic determination indicated a macromolecular redistribution of the gluten proteins from the moment of the wheat harvest until the moment of flour stabilisation.

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.