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.
Sterilization in a liquid of a specific starch makes it slowly digestible in vitro and low glycemic in rats.
Severijnen, C., Abrahamse, E., Van der Beek, E. M., Buco, A., van de Heijning, B. J. M., van Laere, K. & Bouritius, H. (2007). The Journal of Nutrition, 137(10), 2202-2207.
Diabetics are recommended to eat a balanced diet containing normal amounts of carbohydrates, preferably those with a low glycemic index. For solid foods, this can be achieved by choosing whole-grain, fiber-rich products. For (sterilized) liquid products, such as meal replacers, the choices for carbohydrate sources are restricted due to technological limitations. Starches usually have a high glycemic index after sterilization in liquids, whereas low glycemic sugars and sugar replacers can only be used in limited amounts. Using an in vitro digestion assay, we identified a resistant starch (RS) source [modified high amylose starch (mHAS)] that might enable the production of a sterilized liquid product with a low glycemic index. Heating mHAS for 4–5 min in liquid increased the slowly digestible starch (SDS) fraction at the expense of the RS portion. The effect was temperature dependent and reached its maximum above 120°C. Heating at 130°C significantly reduced the RS fraction from 49 to 22%. The product remained stable for at least several months when stored at 4°C. To investigate whether a higher SDS fraction would result in a lower postprandial glycemic response, the sterilized mHAS solution was compared with rapidly digestible maltodextrin. Male Wistar rats received an i.g. bolus of 2.0 g available carbohydrate/kg body weight. Ingestion of heat-treated mHAS resulted in a significant attenuation of the postprandial plasma glucose and insulin responses compared with maltodextrin. mHAS appears to be a starch source which, after sterilization in a liquid product, acquires slow-release properties. The long-term stability of mHAS solutions indicates that this may provide a suitable carbohydrate source for low glycemic index liquid products for inclusion in a diabetes-specific diet.
Development of high amylose wheat through TILLING.
Slade, A. J., McGuire, C., Loeffler, D., Mullenberg, J., Skinner, W., Fazio, G., Holm, A., Brandt, K. M., Steine M. N., Goodstal, J. F. & Knauf, V. C. (2012). BMC Plant Biology, 12(1), 69.
Background: Wheat (Triticum spp.) is an important source of food worldwide and the focus of considerable efforts to identify new combinations of genetic diversity for crop improvement. In particular, wheat starch composition is a major target for changes that could benefit human health. Starches with increased levels of amylose are of interest because of the correlation between higher amylose content and elevated levels of resistant starch, which has been shown to have beneficial effects on health for combating obesity and diabetes. TILLING (Targeting Induced Local Lesions in Genomes) is a means to identify novel genetic variation without the need for direct selection of phenotypes. Results: Using TILLING to identify novel genetic variation in each of the A and B genomes in tetraploid durum wheat and the A, B and D genomes in hexaploid bread wheat, we have identified mutations in the form of single nucleotide polymorphisms (SNPs) in starch branching enzyme IIa genes (SBEIIa). Combining these new alleles of SBEIIa through breeding resulted in the development of high amylose durum and bread wheat varieties containing 47-55% amylose and having elevated resistant starch levels compared to wild-type wheat. High amylose lines also had reduced expression of SBEIIa RNA, changes in starch granule morphology and altered starch granule protein profiles as evaluated by mass spectrometry. Conclusions: We report the use of TILLING to develop new traits in crops with complex genomes without the use of transgenic modifications. Combined mutations in SBEIIa in durum and bread wheat varieties resulted in lines with significantly increased amylose and resistant starch contents.
In vitro fermentation of spent turmeric powder with a mixed culture of pig faecal bacteria.
Han, K. H., Azuma, S. & Fukushima, M. (2014). Food & Function, 10, 2446-2452.
The fermentation potential of spent turmeric was studied in in vitro swine faecal batch cultures. The spent turmeric residue (the enzyme-resistant fraction from spent turmeric, EST) was obtained through the use of the digestive enzymes amyloglucosidase and pancreatin and compared to cellulose and high-amylose starch (HAS) as carbon sources. EST showed significant increases in total anaerobes, bifidobacteria, lactobacilli and lactic acid bacteria populations compared to cellulose at 12, 24 and 48 h, and the total anaerobic level in the HAS group was significantly higher than in the cellulose group at 24 and 48 h. However, a significant decrease in the coliform population was only found in the HAS group compared to the cellulose group at 48 h. The total short-chain fatty acid (SCFA) concentrations in the EST and HAS groups were significantly higher than that in the cellulose group at 12 h and 48h. However, there was no significant difference in the total SCFA concentration between the EST and HAS groups at 12 h and 48h. Ammonia and pH levels in the EST and HAS groups were significantly lower than those in the cellulose group at 24 and 48 h, but there was no significant difference between the EST and HAS groups. These results indicate that the fermentation potential of the enzyme-resistant fraction from spent turmeric is comparable to that of commercially established resistant starch.
Gastrointestinal hormone modulation after a double-blind interventional study with unavailable carbohydrates.
Giuntini, E. B., Sardá, F. A., Lui, M. C. Y., Tadini, C. C., Lajolo, F. M. & Menezes, E. W. (2015). Food Research International, 77(1), 17-23.
The intake of unavailable carbohydrates—functional ingredients—has presented an inverse relationship with the risk for non-communicable diseases. Inulin and unripe banana flour (UBF) (source of resistant starch—55%) are among these ingredients. The aim of this work was to evaluate the impact of regular and discontinued intake of inulin or UBF on the plasma levels of gastrointestinal hormones and energy intake in healthy volunteers. A medium-term clinical assay was conducted with healthy volunteers, both males and females (n = 33), who were oriented to consume soup with added inulin (INU group), UBF (UBF group) or maltodextrin (Control group) three times a week for six weeks. Prototypes of two different types of frozen soups were provided by a food industry. The plasma concentration of satiety-related gastrointestinal hormones was evaluated before and at the end of the intervention. Blood collection was performed 180 min after the consumption of breakfast ad libitum. The energy intake was evaluated at the subsequent meal (180 min). UBF consumption (8 g) caused significant changes in the plasmatic levels of the gastrointestinal hormones when compared to the period before the intervention: there was a lower increase in ghrelin (T0, T60, T120 and T180 min) and a decrease in insulin (T0 and T180 min), hormones related to hunger, when at high levels, as well as an increase in peptide YY (PYY) at all timepoints. When comparing the Control and UBF groups at the end of the intervention, the latter presented a reduction in ghrelin (T0, 120 and 180 min) and insulin (T0 and 180 min) and an increase in PYY (T30 and 180 min). The consumption of inulin (8 g), compared to the period before and at the end of the intervention, resulted in a lower increase in ghrelin (T0, T120 and T180 min) and a decrease in insulin (T180 min). PYY also increased at all timepoints, which indicates higher satiety. When the Control and INU groups were compared at the end of the intervention, the INU group presented reductions in ghrelin (T0, 120 and 180 min) and insulin (T180 min) and an increase in PYY (T180 min). At the subsequent meal, there was a reduction in energy intake of approximately 15% (129 kJ) for the UBF and 12% (130 kJ) for the INU groups. Both inulin and UBF present positive effects on gastrointestinal hormones and energy intake and may be used for producing products that stimulate healthy eating habits.
Identification of carbohydrate parameters in commercial unripe banana flour.
Sardá, F. A. H., de Lima, F. N., Lopes, N. T., Santos, A. D. O., Tobaruela, E. D. C., Kato, E. T. & Menezes, E. W. (2016). Food Research International, 81, 203-209.
Unripe banana flour (UBF), which is rich in resistant starch (RS), has shown several positive physiological effects in clinical trials. Although such observations encourage the emergence of UBF in the food market, specific identity or quality standards for the product are still lacking. This work aimed to assess and propose characterization parameters for commercially available UBF. The results showed that three of the brands examined presented a RS content higher than 40%, whereas nine showed a lower content, with two having less than 10% RS and over 80% total starch, which was fully identified as cereal starch by light microscopy (LM). The presence of banana peel in the flour was correlated with the lipid (r = 0.870), ash (r = 0.812), protein (r = 0.704) and total starch (r = − 0.761) contents. According to principal components analysis (PCA) and LM identification, the main parameters for the characterization of commercial UBFs are the contents of RS, dietary fiber, lipid and ash. The large variability in RS content (4 to 62%) found in commercial UBFs is one reason why consumers would benefit from additional labeling information, such as the inclusion of the RS and soluble sugar (SS) contents, the unripe banana cultivar used, and indications about use of the peel. Moreover, adulterations could be verified by food inspection agencies via LM, which can be used as a tool to identify the type and state of the starch present.