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PubMed1997

Effects of source of starch on net portal flux of glucose, lactate, volatile fatty acids and amino acids in the pig.

The ileal digestibilities of maize starch and native pea starch do not differ. However maize starch is digested faster than pea starch and the ileal amino acid digestibility of a diet containing pea starch is lower. In the present study, the net portal fluxes of glucose, lactate, volatile fatty acids (VFA) and amino acids were measured for diets including 650 g maize starch or pea starch/kg. The diets were fed at a level 870 kJ digestible energy/kg0.75 twice daily (06.00 and 18.00 hours) to four female pigs in a crossover design. Portal vein blood flow did not differ between maize and pea starches (1620 and 1484 ml/min respectively; SED 100; P = 0.23). For maize starch portal glucose flux was significantly higher during the first 6 h after feeding, was not different 8 h after feeding and was significantly lower thereafter. Net portal glucose flux was higher for maize starch than for pea starch (1759 and 1265 mmol/12 h respectively; SED 182; P = 0.054). Net portal lactate flux was not significantly different between maize and pea starches (36.5 and 67.2 mmol/12 h respectively; SED 24.1; P = 0.27) and net portal VFA flux was lower for maize starch than for pea starch (169 and 218 mmol/12 h respectively; SED 18; P = 0.054). Net portal fluxes of valine, isoleucine, phenylalanine, tryptophan, arginine, serine, cystine, tyrosine, lysine, histidine and the sum of essential amino acids tended to be or were higher (P < 0.1 or P < 0.05) and net portal flux of aspartic acid tended to be lower for pea starch (P < 0.1). It can be concluded that, although ileal digestibility of both starches is equal, the rate of appearance of glucose in the portal vein was higher for maize starch, influencing the net portal flux of amino acids.

Amino Acids↗

PubMed1999

In vitro utilization of amylopectin and high-amylose maize (Amylomaize) starch granules by human colonic bacteria.

It has been well established that a certain amount of ingested starch can escape digestion in the human small intestine and consequently enters the large intestine, where it may serve as a carbon source for bacterial fermentation. Thirty-eight types of human colonic bacteria were screened for their capacity to utilize soluble starch, gelatinized amylopectin maize starch, and high-amylose maize starch granules by measuring the clear zones on starch agar plates. The six cultures which produced clear zones on amylopectin maize starch- containing plates were selected for further studies for utilization of amylopectin maize starch and high-amylose maize starch granules A (amylose; Sigma) and B (Culture Pro 958N). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was used to detect bacterial starch-degrading enzymes. It was demonstrated that Bifidobacterium spp., Bacteroides spp., Fusobacterium spp., and strains of Eubacterium, Clostridium, Streptococcus, and Propionibacterium could hydrolyze the gelatinized amylopectin maize starch, while only Bifidobacterium spp. and Clostridium butyricum could efficiently utilize high-amylose maize starch granules. In fact, C. butyricum and Bifidobacterium spp. had higher specific growth rates in the autoclaved medium containing high-amylose maize starch granules and hydrolyzed 80 and 40% of the amylose, respectively. Starch-degrading enzymes were cell bound on Bifidobacterium and Bacteroides cells and were extracellular for C. butyricum. Active staining for starch-degrading enzymes on SDS-PAGE gels showed that the Bifidobacterium cells produced several starch-degrading enzymes with high relative molecular (M(r)) weights (>160,000), medium-sized relative molecular weights (>66,000), and low relative molecular weights (<66,000). It was concluded that Bifidobacterium spp. and C. butyricum degraded and utilized granules of amylomaize starch.

Amylopectin↗

PubMed1991

Chemoreception for an insoluble nonvolatile substance: starch taste?

Substances that are insoluble in both water and lipids, such as starch, are commonly assumed to be tasteless. Starch was suspended in water with a viscous gum. Rats given a choice of fluid containing starch and the same fluid without starch consistently preferred fluids containing starch. Rats were able to detect as little as 0.5% starch from several species of plants (corn, rice, wheat, and potato). In contrast, rats ignored comparable concentrations of cellulose suspended in water. Rats were also capable of choosing the fluid containing higher levels of starch when given a choice of 1 vs. 2% starch or 0.5 vs. 1% starch. This ability to detect starch did not appear to be mediated by salivary alpha-amylase because 1) raw starch is highly resistant to hydrolysis by salivary amylase, 2) starch preference was not correlated with the susceptibility of the starch to hydrolysis by salivary amylase, and 3) starch preference was not blocked by partial or extensive desalivation. Attempts to extract impurities with either organic solvents or water did not provide any evidence that such impurities contribute to starch preference. These experiments point to a seemingly novel form of chemoreception that could be useful to animals that need to identify starch-rich foods.

Amylases↗

PubMed1996

Effect of resistant and digestible starch on intestinal absorption of calcium, iron, and zinc in infant pigs.

The first nonmilk foods that are given to infants contain high levels of starch, a fraction of which is resistant to enzyme hydrolysis. Incomplete digestion of starch may interfere with the absorption of certain minerals. A fraction of dietary starch which is resistant to in vitro enzymatic hydrolysis has been termed resistant starch. The aim of this study was to compare the intestinal apparent absorption of calcium, phosphorus, iron, and zinc in the presence of either resistant or digestible starch. Twelve 7-10-d-old piglets were fitted with a T-tube inserted into the intestine approximately 3 m distal to the duodenum. Animals received in random order 200 mL of a test meal of cooked, cooled, high amylose corn starch (16.4% resistant starch), or cooked rice starch (digestible starch) administered by an orogastric tube. Both meals contained the same amount of calcium, phosphorus, iron, and zinc. The test meal also contained tracer amounts of 59Fe and 65Zn, as well as polyethylene glycol 3350, as a nonabsorbable marker. Intestinal apparent absorption of starch was greater the meal with digestible starch (71.0 +/- 17.0%) than after the meal with resistant starch (49.2 +/- 10.3) (p < 0.001). After feeding the meals with resistant and digestible starch, mineral apparent absorption was, respectively: calcium, 40.2 +/- 11.8% versus 28.1 +/- 16.4% (p < 0.05); phosphorus, 73.2 +/- 14.0% versus 67.8 +/- 18% (NS); iron, 24.1 +/- 12.2% versus 12.6 +/- 10.6% (p < 0.01), and zinc, 35.0 +/- 13.0% versus 30.6 +/- 8.22% (NS). In conclusion, a meal containing 16.4% resistant starch resulted in a greater apparent absorption of calcium and iron compared with a completely digestible starch meal. If this finding holds true for the whole bowel, administration of resistant starches could have a positive effect on intestinal calcium and iron absorption.

Animals↗

PubMed2003

Effects of corn grain conservation method on feeding behavior and productivity of lactating dairy cows at two dietary starch concentrations.

Effects of conservation method of corn grain and dietary starch concentration on dry matter intake (DMI) and productivity of lactating dairy cows were evaluated. Eight ruminally and duodenally cannulated Holstein cows (55 +/- 15.9 d in milk; mean +/- SD) were used in a duplicated 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments. Experimental diets contained either ground high-moisture corn (HM) or dry ground corn (DG) at two dietary starch concentrations (32 vs 21%). Mean particle size and dry matter (DM) concentration of corn grain were 1863 pm and 63.2%, and 885 microm and 89.7%, for HM and DG, respectively. DMI was lower for HM compared to DG treatment in high-starch diets (20.8 vs 22.5 kg/d), but similar for the HM and DG treatments in low-starch diets (19.7 vs 19.6 kg/d). This reduction in DMI is attributed to smaller meal size for HM compared to DG in high-starch diets (1.9 vs 2.3 kg of DM for high-starch diets; 2.1 vs 2.0 kg of DM for low-starch diets). Faster starch fermentation for HM in high-starch diets might result in satiety with smaller meal size. Milk yield was greater when cows were fed high-starch diets compared to low-starch diets (38.6 vs 33.9 kg/d) regardless of corn grain treatment. High-starch diets increased solids-corrected milk yield by 3.3 kg (35.2 vs 31.9 kg/d) compared to low-starch diets for cows fed DG, but did not increase for cows fed HM. This was because of a lower milk fat concentration for cows fed HM in high-starch diets. Reducing ruminal starch fermentation by substituting DG for HM can increase the productivity of lactating cows fed high-starch diets.

Animal Feed↗

PubMed1990

Adhesion of an Amylolytic Arthrobacter sp. to Starch-Containing Plastic Films.

Cells of the amylolytic bacterium KB-1 (thought to be an Arthrobacter sp.) adhered ( approximately 70%) to the surface of plastic films composed of starch-poly (methylacrylate) graft copolymer (starch-PMA), but did not adhere (<10%) to films composed of polymethylacrylate (PMA), polyethylene (PE), carboxymethyl cellulose, or a mixture of PE plus poly (ethylene-coacrylic acid) (EAA), starch plus PE, or starch plus PE and EAA. About 30% of the cells adhered to gelatinized insoluble starch. Dithiothreitol (5 mM), EDTA (5 mM), and soluble starch (1%, wt/vol) had little effect on the adhesion of KB-1 cells to starch-PMA films. However, glutaraldehyde-fixed cells, azide-treated cells, and heat-killed cells did not bind to starch-PMA plastic, suggesting that the observed adhesion required cell viability. Culture supernatant from 5-day-old KB-1 cultures contained a proteolytic enzyme that inhibited cell adhesion to starch-PMA plastics. Trypsin-treated KB-1 cells also lost their ability to bind to starch-PMA plastic. When washed free of trypsin and suspended in fresh medium, trypsin-treated bacteria were able to recover adhesion activity in the absence, but not in the presence, of the protein synthesis inhibitor chloramphenicol. These results suggested that adhesion of KB-1 to starch-PMA plastic may be mediated by a cell surface protein. Although KB-1 bacteria bound to starch-PMA plastic, they did not appear to degrade starch in these films. Evidence of starch degradation was observed for starch-PE-EAA plastics, where <10% of the bacteria was bound, suggesting that cell adhesion may not be a prerequisite for degradation of some starch-containing plastics.

Journal Article↗

PubMed2005

Isolation and partial characterization of mango (Magnifera indica L.) starch: morphological, physicochemical and functional studies.

Mango (Mangifera indica) is a fruit that grows in tropical regions. The aim of this work was to isolate the starch from two varieties of mango highly consumed in Mexico ("criollo" and "manila"), and to evaluate its chemical composition, along with some morphological, physicochemical and functional properties. Mango starch had an amylose content of about 13%, the fat content of "criollo" variety starch (0.1-0.12%), was similar to that of commercial corn starch used as control (0.2%); both mango starches had higher ash amount (0.2-0.4%) than corn starch. Mango starches presented a smaller granule size (10 microm) than corn starch (15 microm), along with an A-type X-ray diffraction pattern with slight tendency to a C-type. All values of water retention capacity (WRC) increased with the temperature. When the temperature increased, solubility and swelling values increased and in general, mango starches had higher values than corn starch. Both mango starches had gelatinization temperatures lower than the control, but "criollo" variety starch presented higher enthalpy values than "manila" variety and corn starches. Overall, it was concluded that due to its morphological, physicochemical and functional properties, mango starches could be a feasible starch source with adequate properties, suitable for using in the food industry.

Adsorption↗

PubMed1993

Relative preference for starch and sugar in rats.

When given a choice between fluids containing equal amounts of corn starch or glucose, Fischer rats preferred the fluid containing starch when the fluids contained 0.5%, 1%, 5%, or 20% carbohydrate, but not when the fluids contained 10% carbohydrate. Fischer rats preferred 0.5% sucrose over 0.5% starch on the first day of testing, but then switched to preferring starch. Rats of the CD strain also preferred 0.5% starch over 0.5% sucrose or 0.5% glucose, but showed no reliable preference when offered a choice of 5% starch vs. 5% sucrose or 5% glucose. Most experiments used corn starch, but rats prefer 1% rice, wheat, and tapioca starch over 1% glucose. Rats given only one substance to drink, drank more fluid if the fluid contained 1% starch than if it contained 1% glucose. Preexposing rats to either glucose or starch for 3 days did not influence subsequent preference for starch over glucose. Since the starch and glucose mixtures used in the present work had the same number of calories, preference for starch over glucose must be attributed to the hedonic effects of starch flavor rather than to the postingestive effects of starch.

Animals↗

PubMed2000

Hydrolytic action of alpha-amylase on high-amylose starch of low molecular mass.

High-amylose starches of low average degree of polymerization (d-p 61-71), formed as fine granules by interaction of Bacillus macerans cyclodextrin glucanotransferase with alpha-cyclodextrin (CD) at 2-70 degrees C, are highly insoluble in water and not gelatinizable under normal cooking conditions (100 degrees C). Samples of CD-derived starches, both cooked and uncooked, were subjected to hydrolysis in vitro by human salivary alpha-amylase at 37 degrees C under conditions chosen to resemble those in the human intestinal lumen. Released low-molecular-mass saccharides were determined quantitatively by HPLC and the results compared with those from similar studies with natural starches. Among uncooked starches, CD-derived starch showed very low reactivity towards alpha-amylase, along with potato starch and a high-amylose hybrid corn starch(64% amylose). Cooking greatly enhanced reactivity of natural starches, but only moderately increased reactivity of CD-derived starches. Susceptibility to hydrolysis of cooked starches increased in the following general order: CD-derived starch (approximately 100% amylose)<100%corn amylose (isolated by the butan-1-ol method)<hybrid high-amylose corn starch (64-66% amylose)<waxy maize starch (99-100%amylopectin) approximately ordinary corn starch ( approximately 25% amylose)<potato starch (approximately 25% amylose).

Amylose↗

PubMed1992

Contribution of the digestive tract microflora to amylomaize starch degradation in the rat.

To study in vivo the contribution of the bacterial flora to amylomaize starch degradation in the rat, germ-free and conventional rats were fed on a diet containing either a normal maize starch or an amylomaize starch. In germ-free rats maize starch was almost totally digested in the small intestine, whereas 40% of the ingested amylomaize starch reached the caecum and 30% was excreted, despite the very high endogenous amylase activity. Study by transmission electron microscopy of germ-free caecal contents showed an endocorrosion of the starch granule. In conventional rats, as in germ-free rats, digestibility of maize starch reached 98% in the small intestine, whereas that of amylomaize starch was only 60%. In the caecum of these rats amylomaize starch was fermented, and this led to a decrease in caecal pH and to formation of short-chain fatty acids (SCFA), especially propionate. Comparison between conventional rats fed on maize starch or amylomaize starch showed that caecal SCFA concentrations during a circadian cycle varied in the same way whereas total SCFA and lactic acid concentrations were much higher in rats fed on amylomaize starch. Amylase (EC 3.2.1.1) activity was similar in the caecal contents of conventional rats whatever the ingested starch. It was lower in conventional than in germ-free rats, but no starch granule remained in the caecum of conventional rats. These results showed that bacterial amylase was more efficient at degrading resistant amylomaize starch than endogenous amylase.

Amylases↗

PubMed1985

Absorption of starch by healthy ileostomates: effect of transit time and of carbohydrate load.

Recently, breath hydrogen studies and intubation techniques have indicated that in excess of 10% of starch in normal foods may be malabsorbed in the small intestine and enter the colon. We evaluated starch absorption in healthy subjects with ileostomy. First, unabsorbed starch was quantified in ileostomy effluent from six ileostomates who ingested constant diets of wheat and potato starch for four days. Daily unabsorbed starch ranged from 1.3% to 5.0% of total ingested starch. Second, starch from a radiolabeled solid meal containing 50 g potato starch was measured under control conditions and after altering transit time with either loperamide, or magnesium citrate. Loperamide significantly decreased the amount of unabsorbed starch in all six ileostomates (p less than 0.05), while magnesium citrate significantly increased starch malabsorption in all six subjects (p less than 0.05). Third, starch absorption was measured after single solid meals containing 25, 50, 75, and 100 g potato starch. There was a linear relationship between starch input and output. Mean output expressed as a percent of input remained constant. We conclude that the degree of starch malabsorption by the small intestine of ileostomates may be less than that estimated by indirect methods in intact humans. The amount of unabsorbed starch is directly related to the quantity ingested and to the small intestinal transit time.

Adult↗

PubMed2000

Characterization of four outer membrane proteins involved in binding starch to the cell surface of Bacteroides thetaiotaomicron.

Bacteroides thetaiotaomicron, a gram-negative obligate anaerobe, utilizes polysaccharides by binding them to its cell surface and allowing cell-associated enzymes to hydrolyze them into digestible fragments. We use the starch utilization system as a model to analyze the initial steps involved in polysaccharide binding and breakdown. In a recent paper, we reported that one of the outer membrane proteins involved, SusG, had starch-degrading activity but was not sufficient for growth on starch. Moreover, SusG alone did not have detectable starch binding activity. Previous studies have shown that starch binding is essential for starch utilization. In this paper, we report that four other outer membrane proteins, SusC through SusF, are responsible for starch binding. Results of (14)C-starch binding assays show that SusC and SusD both contribute a significant amount of starch binding. SusE also appears to contribute substantially to starch binding. Using affinity chromatography, we show in vitro that these Sus proteins interact to bind starch. Moreover, protease accessibility of either SusC or SusD greatly increased when one was expressed without the other. This finding supports the hypothesis that SusC and SusD interact in the outer membrane. Evidence from additional protease accessibility studies suggests that SusC, SusE, and SusF are exposed on the cell surface. Our results demonstrate that SusC and SusD act as the major starch binding proteins on the cell surface, with SusE enhancing binding. SusF's role in starch utilization has yet to be determined, although the fact that starch protected it from proteolytic attack suggests that it does bind starch.

Amylose↗

PubMed2000

Food starches and dental caries.

Sucrose and starches are the predominant dietary carbohydrates in modern societies. While the causal relationship between sucrose and dental caries development is indisputable, the relationship between food starch and dental caries continues to be debated and is the topic of this review. The current view of dental caries etiology suggests that in-depth evaluation of the starch-caries relationship requires the consideration of several critical cariogenic determinants: (1) the intensity (i.e., the amount and frequency) of exposure of tooth surfaces to both sugars and starches, (2) the bioavailability of the starches, (3) the nature of the microbial flora of dental plaque, (4) the pH-lowering capacity of dental plaque, and (5) the flow rate of saliva. Studies of caries in animals, human plaque pH response, and enamel/dentin demineralization leave no doubt that processed food starches in modern human diets possess a significant cariogenic potential. However, the available studies with humans do not provide unequivocal data on their actual cariogenicity. In this regard, we found it helpful to distinguish between two types of situations. The first, exemplified by our forebears, people in developing countries, and special subject groups in more modern countries, is characterized by starch consumption in combination with a low sugar intake, an eating frequency which is essentially limited to two or three meals per day, and a low-to-negligible caries activity. The second, exemplified by people in the more modern societies, e.g., urban populations, is characterized by starch consumption in combination with significantly increased sugar consumption, an eating frequency of three or more times per day, and a significantly elevated caries activity. It is in the first situation that food starches do not appear to be particularly caries-inducive. However, their contribution to caries development in the second situation is uncertain and requires further clarification. Although food starches do not appear to be particularly caries inducive in the first situation, the possibility cannot be excluded that they contribute significantly to caries activity in modern human populations. The commonly used term "dietary starch content" is misleading, since it represents a large array of single manufactured and processed foods of widely varying composition and potential cariogenicity. Hence, increased focus on the cariogenicity of single starchy foods is warranted. Other aspects of starchy foods consumption, deserving greater attention, include the bioavailability of starches in processed foods, their retentive properties, also in relation to sugars present (starches as co-cariogens), their consumption frequency, the effect of hyposalivation on their cariogenicity, and their impact on root caries. The starch-caries issue is a very complex problem, and much remains uncertain. More focused studies are needed. At present, it appears premature to consider or promote food starches in modern diets as safe for teeth.

Animals↗

PubMed2005

Influence of starch intake on growth and skeletal development of weanling horses.

Forty-four weanling horses were used in two experiments to evaluate the effect of starch intake on growth and skeletal development. In Exp. 1, the weanlings were fed either a grain-based, high-starch (31.1%, DM basis) concentrate or a by-product-based, low-starch (0.0%) concentrate with coastal bermudagrass (Cynodon dactylon) hay. Corn oil was used to equalize the energy concentration of the concentrates. The concentrate:hay ratio was 64:36 (as-fed basis), and intake was the same for both diets. Body weight gains were greater by the weanlings consuming the high-starch concentrate (0.81 vs. 0.67 kg/d; P = 0.01). Total body length gain also was greater for the weanlings consuming the high-starch concentrate (15.5 vs. 13.2 cm; P = 0.045). Other body measurements and bone mineral deposition were not influenced by diet or gender. At the end of the experiment, postprandial blood glucose concentrations suggested that the horses on the low-starch diet were less efficient in metabolizing blood glucose than were those that had been consuming the high-starch diets. In Exp. 2, the weanlings were fed either a high-starch (34.7%) or medium-starch (17.0%) concentrate plus coastal bermudagrass hay. Corn oil again was used to equalize the energy content of the medium-starch concentrate to that of the high-starch concentrate. The concentrate:hay ratio was 64:36 (as-fed basis), and the intake was the same for both diets. The diets did not influence rate of gain (0.75 kg/d; P = 0.98), body measurements (P = 0.11 to 0.93), or bone mineral deposition (P = 0.66). Animals on the medium-starch diet tended to have blood glucose concentrations that peaked earlier and were lower at later times than those consuming the high-starch concentrate. Bone osteochondrotic lesions were not related to the diet and were found to decrease during the course of the experiment for both the high-starch and the medium-starch diets (P = 0.006 and 0.016, respectively).

Animal Feed↗

PubMed2002

Structural studies of starches with different water contents.

The proportion of double helices in starches from a series of pea [rb, rug4-b, rug3-a, and lam-c mutants, and the wild type (WT) parental line], potato and maize (normal and low amylose), and wheat (normal) lines, ranged from about 30-50% on a dry weight basis. In relatively dry starch powders, only about half of the double helices were in crystalline order, this proportion being higher for A-type than for B-type starches. Using starch from WT pea as an example, it was found that increasing water content results in an increase in total crystallinity. When the water content was raised to a level similar to that in excess water, the proportion of crystallinity was close to the proportion of double helices (DH). Measuring crystallinity in starches with a high water content is difficult using traditional methods such as x-ray diffraction. A method was developed, therefore, for determining starch structural characteristics in excess water by measuring the enthalpy of gelatinization transition in quasi-equilibrium differential scanning calorimetry (DSC) experiments. It is suggested that DH% = DeltaH(sp)/DeltaH(DH) x 100%, where DeltaH(sp) and DeltaH(DH) represent the specific enthalpies of gelatinisation transition, DeltaH(sp) being measured as J/g dry starch weight and DeltaH(DH) as J/g DH, in starch. Studies on potato and maize starches in excess water and in 0.6M KCl showed, respectively, that DeltaH(DH) was 36.3 and 35.6 J/g for B-type polymorphs and 33.0 and 35.0 J/g for A-type polymorphs. For C-type starches, such as those from pea, intermediate values of DeltaH(DH), related to the proportions A-/B-polymorphs, should be used. The type of crystallinity in starch can be determined by the shift in peak temperature for thermograms in excess water and in excess 0.6M KCl. For B-polymorphs this shift was found to be approximately 2-3 degrees C and for A-polymorphs approximately 7-12 degrees C. The ratio between ordered areas with both A- and B-polymorphs can be determined from the enthalpies of disruption of each area. These enthalpies can be obtained by deconvolution of bimodal thermograms produced by C-type starches in excess 0.6M KCl. This methodical approach can be applied to all starches that give a sharp gelatinisation thermogram in excess water. Using a range of methods, including DSC, it was found that starch granules from the mutant peas are constructed in a similar way to those from the WT, with B-polymorphs in the centre and A-polymorphs at the periphery of all granules. The proportion of A/B-polymorphs, however, differed between the mutants. It was found that in addition to increasing the total crystallinity, increasing the water content within the granules also resulted in an increase in the proportion of B-polymorphs.

Biopolymers↗

PubMed2003

Acid hydrolysis of native and annealed starches and branch-structure of their Naegeli dextrins.

Eight commercial starches, including common corn, waxy corn, wheat, tapioca, potato, Hylon V, Hylon VII, and mung bean starch, were annealed by a multiple-step process, and their gelatinization characteristics were determined. Annealed starches had higher gelatinization temperatures, reduced gelatinization ranges, and increased gelatinization enthalpies than their native starches. The annealed starches with the highest gelatinization enthalpies were subjected to acid hydrolysis with 15.3% H2SO4, and Naegeli dextrins were prepared after 10 days' hydrolysis. Annealing increased the acid susceptibility of native starches in the first (rapid) and the second (slow) phases with potato starch showing the greatest and high amylose starches showing the least changes. Starches with a larger shift in onset gelatinization temperature also displayed a greater percent hydrolysis. The increase in susceptibility to acid hydrolysis was proposed to result from defective and porous structures that resulted after annealing. Although annealing perfected the crystalline structure, it also produced void space, which led to porous structures and possible starch granule defects. The molecular size distribution and chain length distribution of Naegeli dextrins of annealed and native starches were analyzed. The reorganization of the starch molecule during annealing occurred mainly within the crystalline lamellae. Imperfect double helices in the crystalline lamellae improved after annealing, and the branch linkages at the imperfect double helices became protected by the improved crystalline structure. Therefore, more long chains were observed in the Naegeli dextrins of annealed starches than in native starches.

Amylopectin↗

PubMed2004

Flocculation and coalescence of droplets in oil-in-water emulsions formed with highly hydrolysed whey proteins as influenced by starch.

The effects of added unmodified amylopectin starch, modified amylopectin starch and amylose starch on the formation and properties of emulsions (4 wt.% corn oil) made with an extensively hydrolysed commercial whey protein (WPH) product under a range of conditions were examined. The rate of coalescence was calculated based on the changes in the droplet size of the emulsions during storage at 20 degrees C. The rates of creaming and coalescence in emulsions containing amylopectin starches were enhanced with increasing concentration of the starches during storage for up to 7 days. At a given starch concentration, the rate of coalescence was higher in the emulsions containing modified amylopectin starch than in those containing unmodified amylopectin starch, whereas it was lowest in the emulsions containing amylose starch. All emulsions containing unmodified and modified amylopectin starches showed flocculation of oil droplets by a depletion mechanism. However, flocculation was not observed in the emulsions containing amylose starch. The extent of flocculation was considered to correlate with the rate of coalescence of oil droplets. The different rates of coalescence could be explained on the basis of the strength of the depletion potential, which was dependent on the molecular weight and the radius of gyration of the starches. At high levels of starch addition (>1.5%), the rate of coalescence decreased gradually, apparently because of the high viscosity of the aqueous phase caused by the starch.

Chemical Phenomena↗

PubMed2005

Oxidized and acid thinned starch derivatives of hybrid maize: functional characteristics, wide-angle X-ray diffractometry and thermal properties.

Starch isolated from hybrid maize (8535-23) was subjected to oxidation and acid thinning. Proximate analyses revealed that moisture, ash, protein, fat, fibre, and pH reduced after oxidation and acid thinning. Percentage amylose content reduced from 20.42% in native starch to 18.76 and 17.65% in oxidised and acid thinned starch derivatives, respectively. Wide-angle X-ray diffraction patterns indicated strong peaks at 15.9 degrees, 17.2 degrees, 18.8 degrees, and 25.0 degrees 2theta. No significant difference was observed between the X-ray pattern of the native and modified starches. Both swelling power and solubility increased with increase in temperature. Oxidation and acid thinning reduced swelling power and increased solubility starch. At all pHs, both oxidation and acid thinning reduced the swelling capacity of the native starch. Oxidation increased water and oil absorption capacity of the native starch, while both hydrophilic and hydrophobic properties reduced following acid thinning. Least gelation concentration reduced in acid thinned starch but increased in oxidised derivative. Pasting temperature (Tp), peak viscosity (Pv), hot paste viscosity (Hv), and viscosity after 30 min holding at 95 degrees C (H(v30)) reduced following both modifications. However, values for cold paste viscosity (Cv) and setback (SB) reduced in oxidised derivative and increased in acid thinned starch. Light transmittance of the starch pastes reduced with increase in storage days, however, reduction was more pronounced in native and acid thinned starches. Onset temperature (To), peak temperature (Tp) and conclusion temperature (Tc) of gelatinisation reduced in modified starches compared with native hybrid maize starch. Also, gelatinisation enthalpy reduced after oxidation and acid thinning. Enthalpy of regelatinisation increased as days of storage of starch paste increased.

Acids↗