Measurement of total starch in cereal products by amyloglucosidase-alpha-amylase method: collaborative study.
McCleary, B. V., Gibson, T. S. & Mugford, D. C. (1997). Journal of AOAC International, 80, 571-579.
An American Association of Cereal Chemists/AOAC collaborative study was conducted to evaluate the accuracy and reliability of an enzyme assay kit procedure for measurement of total starch in a range of cereal grains and products. The flour sample is incubated at 95 degrees C with thermostable alpha-amylase to catalyze the hydrolysis of starch to maltodextrins, the pH of the slurry is adjusted, and the slurry is treated with a highly purified amyloglucosidase to quantitatively hydrolyze the dextrins to glucose. Glucose is measured with glucose oxidase-peroxidase reagent. Thirty-two collaborators were sent 16 homogeneous test samples as 8 blind duplicates. These samples included chicken feed pellets, white bread, green peas, high-amylose maize starch, white wheat flour, wheat starch, oat bran, and spaghetti. All samples were analyzed by the standard procedure as detailed above; 4 samples (high-amylose maize starch and wheat starch) were also analyzed by a method that requires the samples to be cooked first in dimethyl sulfoxide (DMSO). Relative standard deviations for repeatability (RSD(r)) ranged from 2.1 to 3.9%, and relative standard deviations for reproducibility (RSD(R)) ranged from 2.9 to 5.7%. The RSD(R) value for high amylose maize starch analyzed by the standard (non-DMSO) procedure was 5.7%; the value was reduced to 2.9% when the DMSO procedure was used, and the determined starch values increased from 86.9 to 97.2%.
Measurement of carbohydrates in grain, feed and food.
McCleary, B. V., Charnock, S. J., Rossiter, P. C., O’Shea, M. F., Power, A. M. & Lloyd, R. M. (2006). Journal of the Science of Food and Agriculture, 86(11), 1648-1661.
Procedures for the measurement of starch, starch damage (gelatinised starch), resistant starch and the amylose/amylopectin content of starch, β-glucan, fructan, glucomannan and galactosyl-sucrose oligosaccharides (raffinose, stachyose and verbascose) in plant material, animal feeds and foods are described. Most of these methods have been successfully subjected to interlaboratory evaluation. All methods are based on the use of enzymes either purified by conventional chromatography or produced using molecular biology techniques. Such methods allow specific, accurate and reliable quantification of a particular component. Problems in calculating the actual weight of galactosyl-sucrose oligosaccharides in test samples are discussed in detail.
Magnesium applications to growth medium and foliage affect the starch distribution, increase the grain size and improve the seed germination in wheat.
Ceylan, Y., Kutman, U. B., Mengutay, M. & Cakmak, I. (2016). Plant and Soil, 406(1), 145–156.
Background and Aims: Magnesium (Mg) has diverse functions in plants and plays a critical role in carbohydrate partitioning between source and sink tissues. There is, however, limited information available about the effects of Mg deficiency on grain starch accumulation, yield formation and seed quality in terms of seed germination and seedling establishment in wheat. Methods: In a solution culture experiment, bread wheat (Triticum aestivum) was grown to maturity with low or adequate Mg under greenhouse conditions, and a post-anthesis foliar Mg application was tested on low-Mg plants. The effects of these Mg treatments on i) yield parameters, ii) distribution of starch among sink and source organs, iii) tissue concentrations of Mg and other minerals and iv) seed germination and seedling development were investigated. Results: Low Mg supply did not affect the vegetative biomass production; but substantially reduced the grain yield. Post-anthesis foliar Mg spray significantly minimized yield losses caused by Mg deficiency. Decreases in grain yield by Mg deficiency were due to decreases in individual seed weight rather than seed number per spike. Low Mg depressed the grain and root starch levels, while increasing the leaf starch. Foliar Mg spray largely reversed these effects of Mg deficiency. Seeds obtained from low-Mg plants exhibited severe impairments in germination and seedling establishment. These seed quality traits were also greatly improved by foliar Mg application to maternal plants. Conclusions: Magnesium deficiency reduces grain yield in wheat mainly by limiting the carbohydrate supply to developing seeds and thus by decreasing the seed weight. Since vegetative growth is far less affected than yield formation, Mg deficiency may remain latent until seed-filling. Therefore, foliar Mg application appears to be a promising tool to alleviate Mg deficiency during seed-filling and minimize its impact on yield and seed quality.
Nixtamalization Process Affects Resistant Starch Formation and Glycemic Index of Tamales.
Mariscal‐Moreno, R. M., Cárdenas, F., de Dios, J., Santiago‐Ramos, D., Rayas‐Duarte, P., Veles‐Medina, J. J. & Martínez‐Flores, H. E. (2017). Journal of Food Science, 82(5), 1110-1115.
Tamales were prepared with 3 nixtamalization processes (traditional, ecological, and classic) and evaluated for chemical composition, starch properties, and glycemic index. Resistant starch (RS) in tamales increased 1.6 to 3.7 times compared to raw maize. This increment was due to the starch retrogradation (RS3) and amylose–lipid complexes (RS5) formation. Tamales elaborated with classic and ecological nixtamalization processes exhibited the highest total, soluble and insoluble dietary fiber content, and the highest RS content and lower in vivo glycemic index compared to tamales elaborated with traditional nixtamalization process. Thermal properties of tamales showed 3 endotherms: amylopectin retrogradation (42.7 to 66.6°C), melting of amylose lipid complex type I (78.8 to 105.4), and melting of amylose–lipid complex type II (110.7 to 129.7). Raw maize exhibited X-ray diffraction pattern type A, after nixtamalization and cooking of tamales it changed to V-type polymorph structure, due to amylose–lipid complexes formation. Tamales from ecological nixtamalization processes could represent potential health benefits associated with the reduction on blood glucose response after consumption.
The Proportion of Fermented Milk in Dehydrated Fermented Milk-Parboiled Wheat Composites Significantly Affects Their Composition, Pasting Behaviour, and Flow Properties on Reconstitution.
Shevade, A. V., O'Callaghan, Y. C., O'Brien, N. M., O'Connor, T. P. & Guinee, T. P. (2018). Foods, 7(7).
Dairy and cereal are frequently combined to create composite foods with enhanced nutritional benefits. Dehydrated fermented milk-wheat composites (FMWC) were prepared by blending fermented milk (FM) and parboiled wheat (W), incubating at 35°C for 24 h, drying at 46°C for 48 h, and milling to 1 mm. Increasing the weight ratio of FM to W from 1.5 to 4.0 resulted in reductions in total solids (from 96 to 92%) and starch (from 52 to 39%), and increases in protein (15.2-18.9%), fat (3.7-5.9%), lactose (6.4-11.4%), and lactic acid (2.7-4.2%). FMWC need to be reconstituted prior to consumption. The water-holding capacity, pasting viscosity, and setback viscosity of the reconstituted FMWC (16.7% total solids) decreased with the ratio of FM to W. The reconstituted FMWC exhibited pseudoplastic flow behaviour on shearing from 18 to 120 s-1. Increasing the FM:W ratio coincided with a lower yield stress, consistency index, and viscosity at 120 s-1. The results demonstrate the critical impact of the FM:W ratio on the composition, pasting behavior, and consistency of the reconstituted FMWC. The difference in consistency associated with varying the FM:W ratio is likely to impact on satiety and nutrient value of the FMWCs.