Extrusion of Rice,Bean and Corn Starches: Extrudate Structure and Molecular Changes in Amylose and Amylopectin

The objective of this study was to evaluate the effects of starch source and amylose content on the expansion ratio, density, and texture of expanded extrudates, as well as to investigate the structural and molecular changes that occur in starch granules as a function of extrusion. The starches employed were rice starches (8%, 20%, and 32% amylose), carioca bean starch (35% amylose), and Hylon V^® corn starch (55% amylose). The extrudates from rice starches containing 20% and 32% amylose exhibited the highest expansion ratio, while, extrudates from Hylon V^® corn starch containing 55% amylose exhibited the lowest expansion ratio. The hardness values of the extrudates with 55% amylose were twice those of the extrudates with 20%, 32%, and 35% amylose. An additional finding was that although the amylopectin promoted the expansion of the gelatinized starch matrix, it failed to strengthen and sustain the walls of the extrudate bubbles during expansion.     

Application of the factorial design of experiments to biodiesel production from lard

Synthesis of biodiesel from lard was carried out using potassium hydroxide as a catalyst. A 3² factorial design of experiments was used. The effects of agitation speed and catalyst concentration were studied. A regression model was obtained to predict the methyl ester concentration and adequately describe the experimental range studied.     

Purification of biodiesel from used cooking oils

In Europe, methyl esters cannot be classified as biodiesel until the EN 14214 Standard specifications are fulfilled. The aim of this paper is to examine the efficiency of removing several impurities in biodiesel from used cooking oils by means of three basic operations under conditions that have been kept as close to commercial operating practice as possible: (a) adsorption (magnesium silicate and bentonite); (b) liquid–liquid extraction (distilled water, tap water, glycerol); and (c) ion exchange (cation resin). The results show that all the purification methods can remove soap, methanol and glycerol effectively, while none had an effect on density, kinematic viscosity, FAME content or glyceride content. However, some of them have shown an influence on FFA and water content. The liquid–liquid extraction with glycerol at 15 wt.% and a 2-step contact proved to be the most suitable.     

Effect of extrusion on the antioxidant capacity and color attributes of expanded extrudates prepared from purple potato and yellow pea flour mixes

Abstract: Foods with antioxidant capacity provide protection against cardio‐vascular, certain forms of cancers, and Alzheimer's diseases caused by oxidative damages and contribute health benefits. The effect of extrusion cooking on the antioxidant capacity and color attributes of extruded products prepared from 3 selected formulations of purple potato and yellow pea flours using a co‐rotating twin screw extruder were studied. Expansion ratios of the extruded products varied from 3.93 to 4.75. The total antioxidant capacities (TAC) of the extruded products, using DPPH assay, were 3769 to 4116 μg trolox equivalent/g dry weight sample and not significantly different (P > 0.05) from their respective raw formulations. The total phenolic contents (TP) of the extruded products varied from 2088 to 3766 μg of gallic acid equivalent/g dry weight sample and retained 73% to 83% of the TP from the raw formulations after extrusion. The total anthocyanins contents (TA) in the extrudates were 0.116 to 0.228 mg of malvidin‐3‐glucosides/g dry weight sample. Compared with their raw formulations, significant losses (60% to 70%) of the TA in the extruded products occurred due to extrusion cooking. Browning indices and color attributes such as brightness, chroma, and hue angle agreed with degradation of anthocyanins in the extruded products. However, extrusion cooking retained antioxidant capacities of the raw formulations in the extruded products either in their natural forms or degraded products with radical scavenging activity. This study demonstrated the potential for the production of puffed extruded food products with the improved antioxidant content from colored potatoes and pulse formulations.     

Physical characteristics of extrudates from corn flour and dehulled carioca bean flour blend

Extruded products were prepared from a corn flour and dehulled carioca bean (Phaseolus vulgaris, L.) flour blend using a single-screw extruder. A central composite rotate design was used to evaluate the effects of extrusion process variables: screw speed (318.9–392.9 rpm), feed moisture (10.9–21.0 g/100 g) and bean flour level (4.8–55.2 g/100 g) on the specific mechanical energy (SME), sectional expansion index (SEI), longitudinal expansion index (LEI), volumetric expansion index (VEI) and density (D) of the extrudates. The instrumental texture was also analyzed. The independent variables had significant effects on the physical properties (SEI, VEI and density) of extrudates, with the exception of SME and LEI. SEI increased with increasing screw speed, but a higher moisture and bean flour content resulted in decreasing SEI and VEI. The increase of moisture and bean flour increased the density of extrudates. According to texture analysis, some treatments with 30 and 45 g/100 g bean flour did not show significant differences when compared to commercial brand snacks. However, when combined with higher moisture content (≥19 g/100 g) and lower screw speed (≤333 rpm), the results of the expanded product were not satisfactory.     

Continuous CHO cell cultures with improved recombinant protein productivity by using mannose as carbon source: Metabolic analysis and scale-up simulation

The replacement of glucose by mannose as a means to improve recombinant protein productivity was studied for the first time in continuous cultures of Chinese hamster ovary (CHO) cells producing human recombinant tissue plasminogen activator (t-PA). Steady-state operation at two hexose levels in the inlet (2.5 and 10 mM) allowed comparing the effect of sugar type and concentration on cell metabolism and t-PA production independently of changes in specific growth rates produced by different culture conditions. An increase in biomass concentration (15–20%) was observed when using mannose instead of glucose. Moreover, specific hexose consumption rates were 20–25% lower in mannose cultures whereas specific production rates of lactate, an undesirable by-product, were 25–35% lower than in glucose control cultures. The volumetric productivity of t-PA increased up to 30% in 10 mM mannose cultures, without affecting the sialylation levels of the protein. This increase is manly explained by the higher cell concentration, and represents a substantial improvement in the t-PA production process using glucose. Under this condition, the oxygen uptake rate and the specific oxygen consumption rate, both estimated by a stoichiometric analysis, were about 10% and 25% lower in mannose cultures, respectively. These differences lead to significant differences at larger scales, as it was estimated by simulating cell cultures at different bioreactor sizes (5–5000 L). By assuming a set of regular operating conditions in this kind of process, it was determined that mannose-based cultures could allow culturing CHO cells up to 3000 L compared to only 80 L in glucose cultures at the same conditions. These facts indicate that mannose cultures may have a significant advantage over glucose cultures not only in terms of volumetric productivity of the recombinant protein but also for their potential application in large-scale productive processes.     

Downregulation by organic nitrogen of AOX1 promoter used for controlled expression of foreign genes in the yeast Pichia pastoris

Pichia pastoris is a well-established cell factory for recombinant protein synthesis. Various optimization strategies of processes based on AOX1 promoter have been investigated, including methanol co-feeding with glycerol or sorbitol during the induction stage. Compared with carbon sources, comparatively little research has been devoted to the effects of nitrogen sources. Several reports have described the benefits of adding casamino acids (CA) to the recombinant protein production medium, however, without considering its effects at the gene expression level. Using enhanced green fluorescent protein as a reporter protein, monitored using flow cytometry, CA was shown to downregulate AOX1 promoter induction. Despite higher growth rates, cultures containing CA exhibited slower transition to the induced state, whereas metabolite analysis revealed that methanol consumption was reduced in the presence of CA compared with its absence. The repressive effect of CA was further confirmed by analysing the synthesis of extracellular recombinant Candida antarctica lipase under control of the AOX1 promoter. These findings highlight nitrogen source selection as an important consideration for AOX1-based protein production.     

Depersonalization: neurobiological perspectives

Depersonalization remains a fascinating and obscure clinical phenomenon. In addition to earlier Jacksonian neurobiological adumbrations, and conventional psychodynamic accounts, views started to be expressed in the 1930s that depersonalization might be a vestigial form of behavior, and since the 1960s that it might be a phenomenon related to the temporal lobe. Recent advances in the neurobiology of the limbic system, and the application of Geschwind's concept of disconnection in the corticolimbic system, have opened the possibility of developing testable models. This paper includes a review of these ideas and of the clinical features of depersonalization, particularly of its emotional changes, suggesting that they are important for the neurobiological understanding of depersonalization. It also draws attention to clinical similarities between the experiential narratives produced by patients suffering from depersonalization and those with corticolimbic disconnections. On the basis of this, a new model is proposed according to which the state of increased alertness observed in depersonalization results from an activation of prefrontal attentional systems (right dorsolateral prefrontal cortex) and reciprocal inhibition of the anterior cingulate, leading to experiences of "mind emptiness" and "indifference to pain" often seen in depersonalization. On the other hand, a left-sided prefrontal mechanism would inhibit the amygdala resulting in dampened autonomic output, hypoemotionality, and lack of emotional coloring that would in turn, be reported as feelings of "unreality or detachment."