Agriculture and Agri-Food Canada

About: Agriculture and Agri-Food Canada is a facility organization based out in Ottawa, Ontario, Canada. It is known for research contribution in the topics: Population & Soil water. The organization has 10921 authors who have published 21332 publications receiving 748193 citations. The organization is also known as: Department of Agriculture and Agri-Food.

Development and Physicochemical Characterization of New Resistant Citrate Starch from Different Corn Starches

Abstract: Resistant starch has drawn broad interest for both potential health benefits and functional properties. In this study, a technology was developed to increase resistant starch content of corn starch using esterification with citric acid at elevated temperature. Waxy corn, normal corn and high-amylose corn starches were used as model starches. Citric acid (40% of starch dry weight) was reacted with corn starch at different temperatures (120–150°C) for different reaction times (3–9 h). The effect of reaction conditions on resistant starch content in the citrate corn starch was investigated. When conducting the reaction at 140°C for 7 h, the highest resistant starch content was found in waxy corn citrate starch (87.5%) with the highest degree of substitution (DS, 0.16) of all starches. High-amylose corn starch had 86.4% resistant starch content and 0.14 DS, and normal corn starch had 78.8% resistant starch and 0.12 DS. The physicochemical properties of these citrate starches were characterized using various analytical techniques. In the presence of excess water upon heating, citrate starch made from waxy corn starch had no peak in the DSC thermogram, and small peaks were found for normal corn starch (0.4 J/g) and Hylon VII starch (3.0 J/g) in the thermograms. This indicates that citrate substitution changes granule properties. There are no retrogradation peaks in the thermograms when starch was reheated after 2 weeks storage at 5°C. All the citrate starches showed no peaks in RVA pasting curves, indicating citrate substitution changes the pasting properties of corn starch as well. Moreover, citrate starch from waxy corn is more thermally stable than the other citrate starches.

Metabolic control analysis is helpful for informed genetic manipulation of oilseed rape (Brassica napus) to increase seed oil content.

Abstract: Top–down control analysis (TDCA) is a useful tool for quantifying constraints on metabolic pathways that might be overcome by biotechnological approaches. Previous studies on lipid accumulation in oilseed rape have suggested that diacylglycerol acyltransferase (DGAT), which catalyses the final step in seed oil biosynthesis, might be an effective target for enhancing seed oil content. Here, increased seed oil content, increased DGAT activity, and reduced substrate:product ratio are demonstrated, as well as reduced flux control by complex lipid assembly, as determined by TDCA in Brassica napus (canola) lines which overexpress the gene encoding type-1 DGAT. Lines overexpressing DGAT1 also exhibited considerably enhanced seed oil content under drought conditions. These results support the use of TDCA in guiding the rational selection of molecular targets for oilseed modification. The most effective lines had a seed oil increase of 14%. Moreover, overexpression of DGAT1 under drought conditions reduced this environmental penalty on seed oil content.

Elucidation of the source and turnover of water soluble and microbial biomass carbon in agricultural soils

Abstract: Understanding the dynamics of soil C is key to managing soil organic matter to enhance soil quality and ecosystem functioning, and reduce trace gas emissions from soils. Our objective was to determine the source and turnover of C pools in some agricultural soils in eastern Canada. Soils from five field experiments under continuous maize cropping for 4–37 yr were sampled, and the organic C content and stable C isotope (13C) composition of whole soil and water soluble and microbial biomass fractions determined. The 13C results showed a clear distinction between the water soluble organic C and microbial biomass C, with the water soluble organic C more like the whole soil and the microbial biomass more like the maize residues. A simple linear model was used to explore the relationship among the soil organic constituents and evaluate the turnover of these carbon pools. Even though the water soluble organic C had a higher turnover rate than the microbial biomass C, the proportion of C4-derived C in the biomass was about 2.5 times greater than that in water soluble organic C. Apparently the large amount of native soil C, the small amount of water soluble organic C, and its equilibrium with the native soil C, cause humus to dominate the isotopic composition of water soluble organic C even though the water soluble C is very active. Our results suggest that the quantity, as well as the turnover rate, of soil organic matter constituents that are in equilibrium influence the isotopic composition of such constituents.