S. Shea Miller

Microscopy and other imaging techniques in food structure analysis

Abstract Microscopy and imaging techniques are the most appropriate techniques for evaluating food structure because they are the only analytical methods that produce results in the form of images rather than numbers. However, images may now also be converted into numerical data to allow for statistical evaluation. Advances in microscopy and imaging techniques are made, for the most part, outside the field of food science, drawing from the fields of materials science, biology and medicine. Such techniques cannot, in most cases, be directly applied to study food structure. They must be adapted because the processing conditions that turn biological raw materials into food cause structural and textural changes which, in turn, change the innate properties and behaviour of the foods. This necessitates the development of appropriate methods and also the specialization of researchers. Future developments in this field can be divided into the use of new equipment developed for use in other fields, and the application of techniques modified to solve specific food science problems, such as the development of new foods with particular properties and texture or the detection of defects in foods.

Processing Affects the Physicochemical Properties of β-Glucan in Oat Bran Cereal

The tendency of mixed linkage oat beta-glucan to form viscous solutions is generally assumed to be related to its ability to lower serum cholesterol levels in humans. However, the association has not been clearly demonstrated. To conduct a clinical trial showing the relationship between LDL-cholesterol levels and viscosity, a series of extruded oat bran cereals were prepared in which the beta-glucan had a range of molecular weights and modified solubility. An extraction protocol using physiological enzymes at 37 degrees C was used to estimate the effect that the cereals would have on gut viscosity. By reducing the molecular weight from 1,930,000 to 251,000 g/mol, the apparent viscosity in the physiological extract dropped from 2900 to 131 mPa.s (at 30 s(-1)). Microscopic examination showed that as the extrusion conditions were made more severe, to cause depolymerization, the integrity of the cell walls was lost and beta-glucan dispersed throughout the cereal. Differences in the hardness and density of the extruded cereals were also evident as the molecular weight was reduced.

Fermentability of Oat and Wheat Fractions Enriched in β-Glucan Using Human Fecal Inoculation

ABSTRACT Fermentation by human fecal bacteria of fractions of wheat bran prepared by preprocessing technology were examined and compared with a β-glucan-rich oat bran and a purified β-glucan (OG). The wheat fractions were essentially a beeswing bran (WBA), mainly insoluble dietary fiber, and an aleurone-rich fraction (WBB) containing more soluble fiber and some β-glucan (2.7%). The oat bran (OB) had more endosperm and was very rich in β-glucan (21.8%). Predigestion of WBB and OB to mimic the upper gastrointestinal (GI) tract gave digested wheat bran fraction B (WBBD) and digested oat bran (OBD), respectively. These predigested fractions were fermented in a batch technique using fresh human feces under anaerobic conditions. Changes in pH, total gas and hydrogen production, short chain fatty acids (SCFA), and both soluble and insoluble β-glucan and other polysaccharide components, as determined from analysis of monosaccharide residues, were monitored. Fractions showed increasing fermentation in the order WB...

The seed coat-specific expression of a subtilisin-like gene, SCS1, from soybean

Abstract. A seed coat-specific gene, SCS1 (Seed Coat Subtilisin 1), from soybean, Glycine max [L.] Merill, has been identified and studied. The gene belongs to a small family of genes with sequence similarity to the subtilisins, which are serine proteases. Northern blot analysis showed that SCS1 RNA accumulates to maximal levels in seed coats at 12 days post anthesis, preceding the final stages of seed coat differentiation. The SCS1 RNA was not found in other tissues including embryos, seed pods, flowers, stems, roots or leaves. In-situ hybridization studies confirmed the temporal pattern of expression observed by Northern blot analysis and further revealed a restricted pattern of RNA accumulation in thick-walled parenchyma cells of the seed coats. These cells are important in the apoplastic translocation of nutrients en route to the embryo from the vascular tissues. The tissue-specific subtilisin-like gene may be required for regulating the differentiation of the thick-walled parenchyma cells.

PAM: Particle Automata in Modeling of Multiscale Biological Systems

Serious problems with bridging multiple scales in the scope of a single numerical model make computer simulations too demanding computationally and highly unreliable. We present a new concept of modeling framework that integrates the particle method with graph dynamical systems, called the particle automata model (PAM). We assume that the mechanical response of a macroscopic system on internal or external stimuli can be simulated by the spatiotemporal dynamics of a graph of interacting particles representing fine-grained components of biological tissue, such as cells, cell clusters, or microtissue fragments. Meanwhile, the dynamics of microscopic processes can be represented by evolution of internal particle states represented by vectors of finite-state automata. To demonstrate the broad scope of application of PAM, we present three models of very different biological phenomena: blood clotting, tumor proliferation, and fungal wheat infection. We conclude that the generic and flexible modeling framework provided by PAM may contribute to more intuitive and faster development of computational models of complex multiscale biological processes.

Introduction of soft X-ray spectromicroscopy as an advanced technique for plant biopolymers research.

Soft X-ray absorption spectroscopy coupled with nano-scale microscopy has been widely used in material science, environmental science, and physical sciences. In this work, the advantages of soft X-ray absorption spectromicroscopy for plant biopolymer research were demonstrated by determining the chemical sensitivity of the technique to identify common plant biopolymers and to map the distributions of biopolymers in plant samples. The chemical sensitivity of soft X-ray spectroscopy to study biopolymers was determined by recording the spectra of common plant biopolymers using soft X-ray and Fourier Transform mid Infrared (FT-IR) spectroscopy techniques. The soft X-ray spectra of lignin, cellulose, and polygalacturonic acid have distinct spectral features. However, there were no distinct differences between cellulose and hemicellulose spectra. Mid infrared spectra of all biopolymers were unique and there were differences between the spectra of water soluble and insoluble xylans. The advantage of nano-scale spatial resolution exploited using soft X-ray spectromicroscopy for plant biopolymer research was demonstrated by mapping plant cell wall biopolymers in a lentil stem section and compared with the FT-IR spectromicroscopy data from the same sample. The soft X-ray spectromicroscopy enables mapping of biopolymers at the sub-cellular (~30 nm) resolution whereas, the limited spatial resolution in the micron scale range in the FT-IR spectromicroscopy made it difficult to identify the localized distribution of biopolymers. The advantages and limitations of soft X-ray and FT-IR spectromicroscopy techniques for biopolymer research are also discussed.

Tapetal oleosins play an essential role in tapetosome formation and protein relocation to the pollen coat.

The Arabidopsis pollen grain is covered by a lipidic pollen coat representing select constituents released upon the programmed cell death of the anther secretory tapetum. These constituents originate primarily from two specialized tapetal organelles, elaioplasts and tapetosomes. Tapetosomes are distinctive Brassicaceae organelles derived from the endoplasmic reticulum that store triacylglycerols, flavonoids, alkanes, and proteins. The tapetosome triacylglycerols are found within lipid droplets surrounded by the highly variable tapetal oleosins that eventually generate the most abundant proteins of the pollen coat. Many questions remain regarding the sub-cellular targeting of tapetal oleosins as well as their role in tapetosome formation. Translational fusions of different tapetal oleosins or their derived domains to marker proteins were introduced into Arabidopsis thaliana to investigate their localization, processing and function. Arabidopsis tapetal oleosins were shown to be proteolytically cleaved following tapetum degeneration and different protein domains were targeted to the pollen coat despite vast differences in composition and size. Importantly, specific fusions were discovered to affect distinct aspects of tapetosome formation. This report not only highlighted the critical role of individual tapetal oleosin domains in Arabidopsis tapetosome formation, but revealed translational fusions to be a valuable tool in deciphering this evidently complex developmental process.

Characterising canola pollen germination across a temperature gradient

Abstract. If predictions are correct, heat stress during reproduction will become a yield limiting factor in many world crops and breeding heat stress tolerance a major goal. The objective of our paper was to highlight a novel system to investigate the influence of temperature (T) on pollen germination using a thermal gradient PCR programmed to establish differential Ts across 12 wells of a PCR plate. Seven cultivars of Brassica napus L. were grown through flowering in a cool growth cabinet (20/15°C day/night) or a heat stress cabinet (HST, 27/22°C day/night). Pollen from each cultivar × cabinet combination was aspirated from 6 opened flowers, and suspended in germination media. Drops of the pollen suspension were floated on media in each well, and the PCR T was set to 30°C with a gradient of ± 10°C, creating a range from ∼20 to 40°C from left to right. After an 8 h treatment, the pollen germination (pg, %) and pollen tube growth score (ptg, 1–5) were evaluated using a microscope. There were significant differences among cultivars for pg and ptg score and significant differences among well T for pg and ptg score. Pollen tubes grew best at T from 20 to 23°C. Well T exceeding 33°C reduced pg and ptg score, although 3 of the 8 cultivars had good pg even at 36°C. HST >29°C, in a growth cabinet, generally resulted in B. napus raceme sterility, although our experiment showed that pollen was still capable of germinating up to 33°C, indicating that pollen germination may not be the only reason for heat stress susceptibility.

Quantitative Microscopic Approaches to Carbohydrate Characterization and Distribution in Cereal Grains

Development and utilization of improved cereal varieties for domestic and international use depends upon the ability of both breeders and processors to: (a) identify potential sources of new or improved traits; (b) incorporate these traits into agronomically acceptable cultivars; and (c) exploit these characteristics in improving traditional products or developing new ones. To do so the breeder must identify and measure desirable traits in a large number of potential cultivars in a relatively rapid and simple manner, and the processor must have access to rapid and precise methods for defining grain “quality”, the combination of chemical and structural attributes which defines the utility of grains in processing conditions. In most major cereals, including wheat, rice, barley, oats, maize, and sorghum, our ability to identify and characterize these traits in phytochemical terms is quite variable depending on the history of the crop, but in all cases it is rudimentary and somewhat empirical. This is not surprising in view of the large number of molecular species which interact to contribute to the overall biochemistry of the grains. Consequently, the most important tool for identifying new cereal varieties is pilot or micro-scale processing, (e.g. pilot milling, malting, baking or extrusion) in which relatively large numbers of samples can be analyzed for their suitability for use in food systems. Although the majority of the storage reserves in cereal grains are polysaccharides (e.g. starch, pentosans, β-glucans) or carbohydrate-linked complexes (e.g. phenolic glycosides, lignin), with few exceptions (e.g., β-glucan determination1) individual chemical traits are either too costly or cumbersome to measure routinely in large numbers, or are ill-defined and inappropriate for daily use.

Treatment of potato farm wastewater with sand filtration.

ABSTRACT This study examined sand filtration as a component of a potato farm wastewater treatment system. Two different sand filter designs, saturated flow and unsaturated flow, were evaluated at three different loading rates: 34, 68, and 136 L m−2 d−1. Filter design had a significant effect, with unsaturated flow sand filters having significantly (p < .05) better total suspended solids (TSS) removal (89%) than saturated flow sand filters did (79%). Loading rate also had a significant (p < .05) effect, given that the lowest loading rate had higher mass removal for TSS than the higher loading rates did. Overall, all sand filters removed TSS, 5-d biochemical oxygen demand, and total phosphorus well (62–99%). Total nitrogen removal was twice as high in unsaturated flow filters (53%) than in saturated flow filters (27%), because of the recurring cycle of aerobic and anaerobic conditions during sand saturation and drying in unsaturated flow sand filters.