Microbial growth and modification of corn distillers dried grains with solubles during fermentation

Corn distillers dried grains with solubles (DDGS) were fermented with bacteria or yeast. The microbial growth on three DDGS media-unmodified DDGS, enzyme-pretreated DDGS, and supplemented DDGS - was compared with standard media. Comparative growth profile indicated peaks in microbial growths at different times. The highest specific growth rates (SGR) of 0.6, 0.54 and 0.51 h⁻¹ were observed for Saccharomyces Boulardii on unmodified DDGS, yeast extract, and enzyme-modified DDGS, respectively. Pediococcus Acidilactici and Lactobacillus Plantarum had the SGR of 0.17 and 0.07 h⁻¹, respectively, on control DDGS. However, L. Plantarum on unmodified DDGS demonstrated the highest cell count (2.91 × 10¹¹ CFU/mL), followed by S. boulardii at 1.5 × 10⁹ CFU/mL on YEPD, and P. acidilactici at 1.16 × 10¹⁰ CFU/mL on MRS (de Man, Rogosa and Sharpe) media. Protein digestibility of DDGS improved slightly due to fermentation, and resulted in reduced phytic acid content for some treatments. Production of lactic acid was highest on unmodified DDGS.     

Composition and oxidative stability of crude oil extracts of corn germ and distillers grains

The fatty acid composition, Acid Value, and the content and composition of tocopherols, tocotrienols, carotenoids, phytosterols, and steryl ferulates were determined in corn germ oil and four post-fermentation corn oils from the ethanol dry grind process. The oxidative stability index at 110 °C was determined for the five oils, and four oils were compared for their stability during storage at 40 °C as determined by peroxide value and hexanal content. The fatty acid composition of all five oils was typical for corn oil. The Acid Value (and percentage of free fatty acids) was highest (28.3 mg KOH/g oil) in corn oil extracted centrifugally from a conventional dry grind ethanol processing facility and for oil extracted, using hexane, from distillers dried grains with solubles (DDGS) from a raw starch ethanol processing facility (20.8 mg KOH/g oil). Acid Value was lowest in two oils extracted centrifugally from thin stillage in a raw starch ethanol facility (5.7 and 6.9 mg KOH/g oil). Tocopherols were highest in corn germ oil (∼1400 μg/g), but tocotrienols, phytosterols, steryl ferulates, and carotenoids were higher in all of the post-fermentation corn oils. Hexane extracted oil from DDGS was the most oxidatively stable as evaluated by OSI and storage test at 40 °C, followed by centrifugally extracted thin stillage oil from the raw starch ethanol process, and centrifugally extracted thin stillage oil from the conventional dry grind ethanol process. Corn germ oil was the least oxidatively stable. When stored at room temperature, the peroxide value of centrifugally extracted thin stillage oil from the raw starch ethanol process did not significantly increase until after six weeks of storage, and was less than 2.0 mequiv. peroxide/kg oil after three months of storage. These results indicate that post-fermentation corn oils have higher content of valuable functional lipids than corn germ oil. Some of these functional lipids have antioxidant activity which increases the oxidative stability of the post-fermentation oils.     

Design properties for molded,corn-based DDGS-filled phenolic resin

With the rapid growth in the ethanol fuel industry in recent years, considerable research is being devoted to maximizing the use of processing coproducts, such as distillers dried grains with solubles (DDGS), typically for livestock diets. Because these residues contain high fiber levels, they may be amendable to incorporation into polymers as well, which is an option that could garner greater economic returns. Thus, the goal of this study was to demonstrate the viability of using corn-based DDGS as a biofiller with phenolic resin, in order to produce a novel biomaterial. DDGS was blended with phenolic resin at four levels (0%, 25%, 50%, and 75%, by weight), and then compression molded at 13.8, 34.5, or 48.3 MPa (1.0, 2.5, or 3.5 tons/in.²) and 157, 174, or 191 °C (315, 345, or 375 F). Molded specimens were then tested for a variety of mechanical and physical properties. Pressure and temperature each had little effect on the resulting properties. DDGS, on the other hand, greatly influenced all of the properties. Tensile yield strengths ranged from 14.5 MPa (2102 psi) to 4.3 MPa (621 psi), while the Young's modulus ranged from 2296 MPa (333,000 psi) to 841 MPa (122,000 psi) as the DDGS content increased. For all time periods studied, water absorption increased as DDGS level increased. Moreover, as DDGS content increased to a maximum of 75%, biodegradability increased from 0% to 38% while the surface hardness decreased 25%. These results were similar to those from other studies that have investigated biofillers. Follow-up studies should aim to optimize the strength of the DDGS-blended resins through the use of coupling agents or other additives.     

Impact of Agro-industrial Byproducts on Bioconversion,Chemical Composition,in vitro Digestibility,and Microbiota of the Black Soldier Fly (Diptera: Stratiomyidae) Larvae

The interest in using byproducts from agro-food industries as a rearing substrate for insects is increasing rapidly. We investigated the influence of byproducts of vegetal origin (okara—a byproduct of soy milk production, maize distillers with solubles, brewer’s grains), used as rearing diet for black soldier fly larvae (BSFL), on the following parameters: biomass production, substrate reduction (SR), nutritional profile and in vitro digestibility, and larval gut microbiota. Hen diet was used as a control substrate. The highest larval biomass was collected on maize distillers, whereas the highest SR was observed on okara. The rearing substrate affected ash, ether extract, and chitin larval content. The BSFL reared on okara were characterized by a lower lauric acid content (17.6% of total fatty acids). Diets also influenced in vitro crude protein digestibility (%) for monogastrics, with the highest values for BSFL reared on maize distillers (87.8), intermediate for brewer’s grains and okara BSFL, and the lowest for hen BSFL (82.7). The nutritive value for ruminants showed a lower Net Energy for lactation for BSFL reared on hen diet than okara and dried maize distillers BSFL. The different byproducts showed an influence on the larval gut microbiota, with a major bacterial complexity observed on larvae fed with the hen diet. The neutral detergent fiber concentration of dietary substrate was negatively correlated with Firmicutes and Actinobacteria relative abundance. Insects valorized byproducts converting them into high-value larval biomass to be used for feed production. The results evidenced the effects of the tested byproducts on the measured parameters, underling the chemical composition importance on the final insect meal quality.     

Two fraction extraction of α-zein from DDGS and its characterization

Zein was recovered from corn distiller's dried grains with solubles (DDGS) by a modified method using 70% (w/w) aqueous 2-propanol (70-IPA) or 70% (v/v) aqueous ethanol (70-EtOH) solvents, and a commercial method using 88% (w/w) aqueous 2-propanol (88-IPA). Yield, purity, and film properties of the isolated zein were determined. The modified procedure extracted two fractions of zeins: a mostly α-zein fraction, and a mostly γ-zein fraction. The modified method increased α-zein yield from 4% to 14%. Enzyme cellulase pretreatment did not improve zein yield, but grinding did. The α-zein fraction showed electrophoretic bands at 40, 22, 19, and 10 kDa, corresponding to α-zein dimer, α₁-zein, α₂-zein, and δ-zein, respectively. The α-zein of DDGS retained its film forming capability. The α-zein film of unmodified DDGS was cloudy and rough, unlike the clear and smooth films of α-zeins isolated from corn gluten meal and enzyme-treated DDGS.     

Glass transitions and the fracture behaviour of gluten and starches within the glassy state

Granular particles (crumbs) of gluten, wheat starch, and waxy maize starch were obtained by extrusion in a twin-screw cooker extruder and conditioned to a range of moisture contents (4–18%). The textures of the granules were assessed by a small sensory panel and the sounds produced during crushing (acoustic emission) measured. Solid, essentially amorphous, bars of gluten, wheat starch and waxy maize starch were produced by heat setting under pressure. The glass transition temperatures were measured by differential scanning calorimetry and dynamic mechanical thermal analysis, crystallinity by X-ray diffraction and the fracture behaviour examined using a three-point bend test. Heat-set gluten failed via elastic (brittle) fracture below its glass transition temperature, whereas, as the moisture content was increased, the glassy gelatinised starches underwent a brittle-ductile transition while still in the glassy state. This change in fracture mechanism explains why extruded gluten granules exhibited crispness at higher moisture contents than extruded starch granules, despite gluten having a lower glass transition temperature. The results suggest that the prediction of brittle textures (crisp, crunchy) from a knowledge of the glass transition temperature alone is not possible because bipolymers can exhibit different fracture mechanisms when in the glassy state.     

Factors that affect high voltage atmospheric cold plasma treatment efficacy on wet distillers’ grains: Shelf-life and nutrient composition

The increase in ethanol production continues to drive the availability of distillers' grains, which are used as an animal feed for cattle, swine and poultry. In its wet state this co-product of the ethanol production process must be fed or treated before spoiling and reaching its shelf-life, only 3–5 days after production. Novel treatment technologies, such as high voltage atmospheric cold plasma (HVACP), continue to show promise as a method to increase the shelf-life of many products such as contaminated animal feed. This study investigated the parameters grain depth, amount of sample and exposure time, for effective treatment of distillers’ grains to increase shelf-life using HVACP. This work evaluates the different combinations of treatments to determine, which parameters are critical for reduction in microbial growth and increase shelf-life. The efficacy of the reactive gas species (RGS) produced by HVACP, at 70 kV for up to 360 s, moving through the grain mass of distillers wet grains (DWG) was evaluated by measuring microbial load (log reduction), moisture content and pH after 0, 14 and 28 days of storage at 25 °C at grain depths of 1, 2.5 and 4.5 cm. Results showed a higher log reduction at the 1 cm depth than at 2.5 and 4.5 cm for measurements after the initial treatment. Stored samples continued to show reductions, however the greater depths had higher log reductions than the surface. Nutrient composition and amino acid profiles were also analyzed, showing no significant difference between treated and untreated samples over the storage period.     

Thermomechanical Glass Transition of Extruded Cereal Melts

Cereal melts were produced via extrusion cooking using a twin-screw extruder at in-barrel moisture contents ranging from 25 to 42% (wb). Dynamic mechanical thermal analysis was performed to determine the plasticizing effect of water on the glass transition (T_g) for melts obtained from degermed corn meal, oat flour, pregelatinized corn starch and pregelatinized waxy maize. For degermed corn meal, T_gwas found to decrease with increasing water contents up to about 30% (wb). Above 30% moisture content, T_gwas found to be essentially constant and approximately equal to 270K. Thus, W_g′ was estimated to be 30% moisture content. For samples of moisture content less than W_g′, loss tangent vs. temperature plots in the glass transition region were observed to be broader and of smaller amplitude than those above W_g. Glass transitions ranged from 270 to 321K for sample moisture contents ranging from 36·3 to 22·2% (wb), respectively. For an oat flour, T_gvalues ranging from 270 to 303K were observed for moisture contents of 39·2 to 26·1% (wb), respectively. Melts formed from pregelatinized corn starch and pregelatinized waxy maize had glass transitions similar to corn meal at a similar moisture content of 27%. The significance of these results, in terms of extrusion cooking of cereals, is discussed in this work.     

Characterisation of Glass Transition of Durum Wheat Semolina using Modulated Differential Scanning Calorimetry

The glass transition of wheat durum semolina was characterised at different moisture contents using modulated differential scanning calorimetry. The total, reversing and non-reversing heat flows were quantified during heating, cooling and re-heating. An endothermic peak was observed on the non-reversing heat flow during first heating and was not greatly affected by changes in moisture content (below 20 g water/100 g dry matter). This peak was associated with endothermic relaxation of the protein fraction in wheat semolina. An endothermic baseline shift was observed on the reversing heat flow during first heating, cooling and re-heating. The temperature at baseline shift decreased (from 110 °C to 27 °C) when moisture content increased (from 6% to 27% db). The measured heat capacity change (0·10–0·25 J/g/°C) was not significantly affected by moisture content. This endothermic baseline shift was presumed to be the glass transition of amorphous polymers in wheat durum semolina. The plasticising effect of water on the glass transition temperature (Tg) was described using Gordon Taylor and Kwei models and compared with Tg of the main wheat components.     

Effect of chemical structure on the properties of UV-cured polyurethane acrylates films

The effect of compositions of isophorone diisocyanate (IPDI)/4,4′-diphenylmethane diisocyanate (MDI) and polypropylene oxide diol (PPG,M _w : 3000)/1,4-butane diol (BD) on the properties of UV-cured polyurethane acrylate films based on 2-hydroxyethyl acrylate (HEA) was examined. UV-curable polyurethane acrylates were formulated from the prepolymer, trimethylol propane triacrylate (TMPTA) as a reactive diluent, and 1-hydroxycyclohexyl ketone (Irgacure 184) as a photoinitiator. Dynamic mechanical thermal properties and elastic properties of UV-cured polyurethane acrylates was found to depend on the chemical composition of IPDI/MDI and PPG/BD. As the BD content increased, the tensile storage modulus of all series samples increased significantly. The storage modulus increased in the order of samples A (IPDI based samples)>samples B (IPDI/MDI (7/3 molar ratio) based samples)>samples C (IPDI/MDI (5/5 molar ratio) based samples at the same composition. Two distinct loss modulus peaks for all samples are observed owing to the soft segment glass transition temperature (T _gs ) and hard segment glass transition temperature (T _gh ). The difference betweenT _gs andT _gh (ΔT _g ) increases in the order of A>B>C at the same composition. In cycle test, the initial onset strain (%) was found to decrease with increasing BD content in PPG/BD and with increasing MDI content in IPDI/MDI.     

Increased pollen viability resulting from transport to the upper boundary layer

Previous studies have examined the rate of viability loss in pollen grains based on surface conditions but some pollen grains are lifted throughout the atmospheric boundary layer to heights where temperature and moisture differ markedly from near the surface. This transport may affect pollen viability in maize pollen which has been linked to its moisture content. The objective of this study was to examine how predictions of pollen viability may differ when considering the effects of boundary layer transport rather than only considering the conditions at the pollen source. We used Large-Eddy Simulation to simulate pollen dispersion and predict pollen viability upon deposition. We compared the predicted viability that was diagnosed using the atmospheric conditions at the pollen source when a pollen grain was released to viability diagnosed using the atmospheric conditions following the pollen grain's trajectory as it moved through the atmospheric boundary layer. Using surface values provided a reasonable prediction of viability for pollen grains that traveled less than a kilometer from the source field, but underpredicted pollen viability by as much as 20% for pollen that traveled several kilometers. The difference is attributed to the tendency for longer range transport to require lofting of pollen grains into the upper part of the atmospheric boundary layer, where cooler temperature and higher relative humidity are conducive to increased viability. Our results suggest that pollen grains traveling many kilometers are more likely to pollinate a receptive silk than would be expected based on the atmospheric conditions at the pollen source.     

Incorporation of aliphatic units into aromatic water-soluble polyesters to improve the performances for warp sizing

Aliphatic units (ethylene succinate) were incorporated into aromatic water-soluble polyesters (WSP) in order to improve their environmental protection and sizing performances. The environmental performance was measured in terms of biological oxygen demand for 5 days (BOD₅) and chemical oxygen demand (COD). Apparent and intrinsic viscosities, the adhesion to polyester fibers, glass transition temperature, and mechanical behavior of sizing films of WSP were evaluated for improving their sizing performance. The composition of copolymeric WSP was also investigated by ¹H-NMR. A series of copolymeric WSP with a variation in molar ratio of aliphatic monomer (dimethyl succinate) to aromatic monomer (dimethyl terephthalate) from 10:90 to 40:60 was synthesized through a two-step reaction, transesterification and polycondensation. It was found that, by incorporating aliphatic units into the macromolecular chain of aromatic WSP, the environmental performance, apparent and intrinsic viscosities, and the toughness of sizing film were enhanced obviously. The adhesion to polyester fibers showed no sensitivity to the molar ratio of dimethyl succinate to dimethyl terephthalate when the ratio ranged from 10:90 to 30:70. In view of overall performance of the aliphatic-containing WSP sizes, the molar ratio should be 30:70. Based on the ratio, the WSP prepared showed better environmental and sizing performances.     

Relationship between the glass transition temperature and the melt flow behavior for gluten, casein and soya

The effects of moisture content (25–45% wwb) and temperature (75–120 °C) on the viscosity of gluten, soya and rennet casein systems was studied using a capillary rheometer. An attempt was made to relate the viscosities to the glass transition temperature measured by differential scanning calorimetry, dynamic mechanical thermal analysis and the phase transition analyzer. The temperature where the material flowed was also determined by the latter technique. All three-protein systems showed shear and extension thinning. Over the shear rate range investigated (1–10³ s⁻¹), gluten had a substantially lower viscosity than the other two proteins, although the difference was less pronounced at the highest temperature studied. This low viscosity is reflected by lower values of the glass transition temperature, the melt flow temperature and the dynamic moduli E′ and E″ in the rubbery state. The results are discussed in terms of the structure and heat induced changes for the three proteins and their relevance to food processing considered.     

Synthesis,structure, and thermal property of poly(trimethylene terephthalate-<Emphasis Type="Italic">co</Emphasis>-trimethylene 2,6-naphthalate) copolymers

Poly(trimethylene terephthalate-co-trimethylene 2,6-naphthalate)s (P(TT-co-TN)s) with various copolymer composition were synthesized, and their chain structure, thermal property and crystalline structure were investigated by using¹H-NMR spectroscopy, differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD), respectively. It was found from sequence analysis that all the P(TT-co-TN) copolymers synthesized have a statistical random distribution of TT and TN units. It was also observed from DSC thermograms that the glass transition temperature increases linearly with increasing the TN comonomer content, whereas the melting temperature of copolymer decreases with increasing the corresponding comonomer content in respective PTT- and PTN-based copolymer, showing pseudo-eutectic melting behavior. All the samples melt-crystallized isothermally except for P(TT-co-66 mol % TN) exhibit multiple melting endotherms and clear X-ray diffraction patterns. The multiple melting behavior originates from the dual lamellar population and/or the melting-recrystallization-remelting. The X-ray diffraction patterns are largely divided into two classes depending on the copolymer composition, i.e., PTT and PTNβ-form diffraction patterns, without exhibiting cocrystallization.     

Water stress during grain development affects starch synthesis,composition and physicochemical properties in triticale

Triticale, a man-made cereal crop developed from a cross between wheat and rye, has excellent agronomic traits to produce starch for bioindustrial applications. The effects of different levels of water stress on expression of starch synthesis genes and starch composition and physicochemical properties were investigated in this study. Three triticale varieties from 5 days post-anthesis were treated with three levels of water stress: low water stress (LWS) at 55–60% of soil moisture, moderate water stress (MWS) at 30–35% soil moisture and severe water stress (SWS) at 10–15% soil moisture. Water stress led to a significant reduction in seed weight at SWS (35–45%). A decrease in starch content was noticeable from MWS onwards and the values were decreased by 42–55% at SWS across all varieties. Such decrease was associated with the reduced expression of starch synthesis genes at 19 days of water stress (DWS). MWS favoured an increase of amylose proportion in triticale starch and it was accompanied by a significant up-regulation of GBSSI expression throughout the grain development. Triticale starch synthesized under water stress showed a reduced population of small granules and an increase of A-type to B-type ratio. SWS caused pitting on starch granules but did not alter the biconcave disc shape of mature granules. An inverse relationship between water stress and a range of starch gelatinization temperature was observed and the MWS environment specifically decreased the peak temperature (Tp) and increased the enthalpy. Our results signify that starch morphology, composition and physicochemical properties in triticale grains could be altered if triticale is grown under drought conditions.     

Physicochemical control of durum wheat grain filling and glutenin polymer assembly under different temperature regimes

Durum wheat is grown in the Mediterranean area where drought and high temperature frequently prevail and impact grain texture, composition and yield. The purpose of this work was to examine the effect of high temperature on grain development and final composition according to the timing of exposure. High temperature (up to 27.5 °C) was applied either during the linear grain filling or drying phases or during whole grain development. The dynamics of grain dry mass, water, glutenin polymers, and protein bodies during grain development were determined. Irrespective of high temperature timing, the arrest of grain filling was observed at 45.9% grain moisture content. At that point, starch granules included in endosperm cells reached their physical packing limit, limiting further deposits. HT applied before physiological maturity shortened the duration of grain filling and resulted in a significant increase in grain protein concentration and in the proportion of vitreous grain. Late formation of sodium dodecyl sulfate (SDS)-insoluble glutenin polymers below 32% grain moisture content was also favored. The ability of wheat storage protein to form a viscoelastic matrix embedding starch granules at the beginning of grain desiccation is proposed to be mandatory for gaining vitreous grains and a high proportion of SDS-insoluble glutenin polymers.     

Chemical properties and water absorption kinetics of transgenic corn grain (2B587 Hx) and its conventional isoline (2B587)

In the hydration process, besides influencing processing conditions, the cultivar may also influence water absorption by the grains and, consequently, yield and quality of the milled products. Therefore, the moisture absorption kinetics of the transgenic corn grain 2B587 Hx and its conventional isoline 2B587 were studied, as well as the chemical characterization of the samples in natural conditions. The water absorption kinetics of the grains was modeled using Peleg's equation at hydration temperatures of 40, 50, 60, and 67 °C. The 2B587 Hx transgenic corn, compared with the 2B587 conventional corn, had higher carbohydrate and ash contents and lower crude fiber content. The water absorption by the grains, which was satisfactorily represented by Peleg's model, occurred more quickly as the temperature increased. Peleg's constant, k₁, which is inversely related to the initial hydration rate, varied from 405.2 to 141.5 min g/g for conventional corn and from 429.5 to 149.5 min g/g for transgenic corn at temperatures from 40 to 67 °C. The choice of the cultivar may depend on the specifications required by the industry for the main final products.     

Analysis of Headspace Compounds of Distillers Grains using SPME in Conjunction with GC/MS and TGA

Chemical composition of headspace compounds of distillers grains was investigated using solid phase microextraction (SPME) along with GC/MS and TGA. Dryer feed (DF) and distillers dried grains (DDG) from a local distillery were utilised for this study. A SUPELCO 75 μm Carboxen/PDMS SPME fibre was found suitable for extraction of analytes from grains. Samples were placed in small vials (40 mL from SUPELCO) filled to one-third of their capacity. SPME was exposed to the headspace for 1 to 2 h. The fibre was then thermally desorbed in GC injection port for separation and identification. The gas chromatogram showed as many as 64 compounds eluting out of the column, the number being greater in DF as compared to DDG. Thermogravimetric analysis (TGA) was performed on the grains to study the oxidative stability of the compounds. SPME fiber was inserted directly into TGA purge gas outlet to study the compounds being evolved. Three weight loss transitions were observed in the TGA curve of DF and DDG. The components from the three transitions were captured by SPME and analysed by GC/MS for identification. TGA helped in determining the degradation stages of grains thereby indicating the temperature limits in drying grains. Difference between the heated and unheated DF and DDG have been discussed in detail.     

The defoliation dynamics of a stockpiled native grassland pasture follow similar patterns between supplemented and unsupplemented beef calves

It is unclear to what extent and on which variables does supplementing beef cattle on native grasslands affect sward structure, specifically on the dynamics of its grazing horizons. Three hypotheses were tested: (i) during a grazing down process under similar forage allowance, supplemented animals take longer to finish each grazing stratum, than their unsupplemented counterparts, (ii) in both cases, the upper stratum will be heavily depleted before the subsequent strata are grazed, (iii) some species and/or forage fractions are consumed faster than others, regardless of the animals being supplemented (corn dried distillers grains with solubles, DDGS, at 0.7% of their body weight, BW, on a dry matter, DM, basis) or not. Three blocks of stockpiled native grasslands were used and split into two treatments plots (n = 6), on which either supplemented (S) or control (C) heifers of 10.6 ± 0.6 months of age and an initial BW of 143 ± 9 kg, were used. A 2.5 × 0.5 m observation grid was installed on the sward, generating 384 observation points on each plot. On these observation plots, sward height (SH) and visually assessed green forage mass percentage (%G) were registered every other day for 12 consecutive days. No differences were found between the horizontal grazing dynamics between supplemented and control animals in terms of how they switched from the upper grazing horizon to the successive ones. In both cases, when the upper grazing horizon was heavily depleted, the subsequent horizon was being depleted by its half. Differences of preference for C3 species over C4 was observed for both treatments, but this effect was more meaningful for control animals. Grazing time never fully compensated for the decline in intake rate during depletion throughout the grazing horizons. Pasture intake declined when the animals transition from grazing the top grazing horizons to the lower horizons, irrespective of the level of supplementation. Managing the sward structure in terms of sward height will be beneficial to maximizing individual animal performance, for both C and S animals. Native grasslands paddocks with a greater C3 gasses predominance will always be preferred to C4 dominated paddocks, regardless of an eventual supplementation practice.