Some dietary polysaccharides like starches can be partially broken down by enzymes like amylase in the human digestive tract. This results in intermediate metabolites like lactic, acrylic, or fumaric acid, which are further broken down by bacteria in the colon to produce short-chain fatty acids (SCFA) such as acetic, propionic, and butyric acids. These SCFAs are absorbed by the colon.
The following in vitro data on microbial fermentation of the two major components of starches, amylose and amylopectin, were available:
188 strains of 10 species of Bacteroides were tested to see if they can ferment plant polysaccharides and mucins. Many of these strains can ferment plant polysaccharides such as amylose, dextran, pectins, and gums. However, the ability to use these substances varies among different Bacteroides species, with amylose and amylopectin being mainly fermented by 8 species.
154 strains of 22 different species of gut bacteria were tested to see if they could break down 21 different types of complex carbohydrates. The bacteria included Bifidobacterium, Peptostreptococcus, Lactobacillus, Ruminococcus, Coprococcus, Eubacterium, and Fusobacterium, which are commonly found in the human colon. Among the carbohydrates tested, many strains of Bifidobacterium, Eubacterium, Peptostreptococcus, and Ruminococcus were able to break down amylose and amylopectin.
Researchers tested the ability of 290 strains of 29 species of bifidobacteria to ferment complex carbohydrates. They found that 22 out of the 29 species tested were able to ferment amylose and amylopectin, which were among the most commonly fermented substrates. The bifidobacteria were of human and animal origin, with most coming from fecal samples.
Ochuba and Von Riesen (1980) studied the fermentation of 10 polysaccharides, including amylopectin, by species of the Enterobacteriaceae family. They found that most of the species, such as Klebsiella, Enterobacter, Aeromonas, E. coli, Vibrio, and Yersinia strains, were able to ferment amylopectin. The authors concluded that this study showed that enteric bacteria can ferment amylopectin.
Oxidised starch (E 1404)
This study compared the digestibility of slightly and highly oxidized corn starch with unmodified corn starch and a reference starch using pancreatic and salivary enzymes. The researchers measured digestibility by the amount of maltose produced after a fixed time period. The results showed that the oxidized starch was 10-15% less digestible by pancreatic enzymes compared to unmodified starch, but there was no significant difference in salivary digestion.
This study looked at the digestibility of different types of starch in rats. One experiment tested the digestibility of a wheat starch that was oxidized with hypochlorite, and found no differences in weight gain or digestibility compared to unmodified wheat starch. Another experiment tested different levels of hypochlorite-oxidized cornstarch in rats, and found that the highly oxidized starch caused poor weight gain and diarrhea, and some rats had enlarged caecums. Another experiment tested different levels of oxidized cornstarch in rats, and found that as the level of oxidation increased, digestibility slightly decreased, but there were no effects on caloric values or organ weights. The study concluded that diarrhea and caecal enlargement can occur in rats fed starches of poor digestibility.
Monostarch phosphate (E 1410)
In vitro studies
A study compared the breakdown of monostarch phosphate by wheat α-amylase with unmodified wheat starch using in vitro enzymatic hydrolysis. There was no difference found in the rate of production of reducing substances.
In vivo studies
This is about an in vivo study comparing the nutritional value of modified and unmodified cornstarches in rats. The study involved six rats of each sex and group and lasted for 21 days. The rats were fed 5 g of a balanced diet supplemented with 1 or 2 g of cornstarch or modified starches. One of the modified starches tested was corn starch phosphate. Results showed that corn starch phosphate produced similar weight gain as the unmodified cornstarch. Another part of the study involved the metabolic behavior of the phosphate radical in starch phosphate, which was studied in vivo by comparing the distribution of 32P after oral administration of labeled starch phosphate to rats with that from either labeled orthophosphate or pyrophosphate. Results showed no significant difference for the three types of phosphate examined. The study concluded that the phosphate moiety of starch phosphate behaves metabolically like any other ionic phosphate.
Distarch phosphate (E 1412)
In vitro studies
In vitro studies look at how substances react in a lab environment. Researchers tested how different types of modified starches break down when exposed to enzymes in test tubes. They found that some modified starches were slightly harder to digest, but that the differences were not significant. They also discovered that higher levels of a cross-linking agent made the modified starches more difficult to digest. Overall, the researchers concluded that phosphate cross-linking did not appear to reduce the rate of hydrolysis with α-amylase.
In vivo studies
This studies that tested the effects of modified starch on rats. In one study, rats were fed a diet with modified or unmodified starch and their body weight and organ weights were measured. No significant differences were found between the groups. In another study, rats were fed diets with different levels of modified starch, and weight gain was identical for all groups. In a third study, rats were fed a diet with modified starch for six weeks, and there were no differences noted between rats fed modified and unmodified starches.
Phosphated distarch phosphate (E 1413)
In vitro studies
The digestibility of a type of modified cornstarch (phosphated distarch phosphate) by pancreatic amylase was slightly lower than that of regular starches (measured as maltose). Another study compared the digestibility of two types of cornstarch (modified and unmodified) using enzymes, and found that the modified starch had similar digestibility to the unmodified starch.
In vivo studies
This study fed 10 male rats a diet supplemented with different types of starch for 10 days. The rats’ weight gain and behavior were monitored. Results showed that there were no significant differences in weight gain or behavioral reactions between rats fed unmodified starch, distarch phosphate (E 1412), or phosphated distarch phosphate (E 1413) at all three levels of supplementation.
Acetylated distarch phosphate (E 1414)
This studies on the digestibility of different types of potato starch. In one study, acetylated distarch phosphate was found to be less digestible (81%) than unmodified potato starch used as a control. In another study, acetylated distarch phosphate was hydrolyzed with pancreatic a-amylase and found to be 75.2% digestible after 60 minutes, compared to 81.3% for the unmodified wheat starch used as a control. Modified potato starches, including acetylated distarch phosphate, were also hydrolyzed with pancreatic a-amylase, and the rate of hydrolysis for acetylated distarch phosphate was 71-97% compared to unmodified starch. Both raw and drum-dried products showed similar results.
Acetylated starch (E 1420)
In vitro studies
In vitro studies found that the digestibility of acetylated starches by fungal amyloglucosidase was 68-81% of that of native starch. In another study, acetylated potato starch (modified to 1.98% acetyl content) had a lower in vitro digestibility (90%) compared to unmodified potato starch. Another study found that acetylated starch had a digestibility of 70.5% after 60 minutes, compared to 81.3% for unmodified wheat starch used as a control.
In vivo studies
This discusses the effects of acetylated starch (E1420) on rats in both in vitro and in vivo studies. In vitro studies found that acetylated starch was less digestible than unmodified starch. In vivo studies found that acetylated starch had a caloric value similar to unmodified starch, but slightly reduced the rate of weight gain in rats. However, acetylated starch did not cause observable tissue damage or irritation. Acetylated starch was also found to be a resistant starch, which raises large bowel SCFA concentrations.
Human studies
A study by Clarke et al. (2007) investigated the digestion of acylated starches in ileostomy volunteers. Volunteers consumed custards containing cooked acetylated, propionylated, or butyrylated high-amylose maize starches, and the amount of starch and esterified short-chain fatty acids (SCFA) excreted in the stoma effluent was measured. Results showed that acetylated starches were resistant to small intestine digestion and had the potential to deliver specific SCFA to the large bowel. The authors concluded that acylated starches could be an effective way to deliver significant quantities of specific SCFA to the colon in humans.
Acetylated distarch adipate (E 1422)
In vitro studies
This is a study about how a substance called acetylated distarch adipate (E 1422) is digested in the lab. The researchers found that when compared to unmodified starch, the acetylated distarch adipate was not completely broken down by a substance called pancreatin. However, when using another substance called amyloglucosidase, the digestibility of acetylated distarch adipate was 98.3%.
In vivo studies
This is describing a study on how the body processes a modified starch called acetylated distarch adipate. In rats, the modified starch was not as easily absorbed as the unmodified starch. However, the modified starch was still metabolized and excreted, with some appearing in the urine, feces, and exhaled air. In a separate study, the caloric value of the modified starch was found to be the same as unmodified starch.
Hydroxypropyl starch (E 1440)
In vitro studies
Hydroxypropyl starch (E 1440) has been studied in vitro to determine its digestibility. One study found no significant difference between low and high substituted starches compared to unmodified starch. Another study found that digestibility decreased exponentially with increasing degree of substitution. At a DS of 0.04 to 0.45, digestibility was 80% to 3.8% of unmodified starch used as control. Hydroxypropyl starch with a DS of 0.06 was found to be 62.3% digestible after 60 minutes, compared to 81.3% for unmodified wheat starch used as control.
In vivo studies
This describes a study on the excretion and digestion of hydroxypropyl starch in rats. In the study, a small amount of the starch was given to a male rat and its excretion was monitored. Over 95% of the radioactivity was excreted in the faeces and 4% in the urine. The starch was also digested in vitro by pancreatin and enzymes from porcine intestinal mucosa. Several compounds were detected after digestion, and the major metabolite isolated was tentatively identified as a mixture of hydroxypropyl maltoses. Further studies confirmed that the digestibility of the starch decreased with increasing DS, and the major metabolite isolated from the faeces of rats was shown to be 4-O-(2-O-[(RS)-2-hydroxypropyl]-a-D-glucopyranosyl)-D-glucopyranose.
Hydroxypropyl distarch phosphate (E 1442)
In vitro studies
This describes in vitro studies on the digestibility of hydroxypropyl distarch phosphate. In the first study, the starch was hydrolyzed with pancreatic enzymes and its digestibility was estimated by measuring changes in reducing power and spectrophotometric absorbance. After 60 minutes, hydroxypropyl distarch phosphate was found to be 60.8% digestible compared to 81.3% for unmodified wheat starch. In the second study, hydrolysis with pancreatic enzymes showed that the rate of hydrolysis for hydroxypropyl distarch phosphate was 58-60% compared to unmodified starch. The digestibility of hydroxypropyl distarch phosphate also depended on the starch’s gelatinisation conditions.
In vivo studies
Researchers fed groups of five rats for seven days with a diet containing either no modified starch, or 1 or 3 grams of modified or control starch. They observed no differences in weight gain.
Starch sodium octenyl succinate (E 1450)
In vitro studies
This is about an in vitro study on the digestibility of Starch sodium octenyl succinate (E 1450). The study compared the digestibility of modified and unmodified starch using different enzymes. The modified starch was found to have a digestibility rate of 83% to 98% compared to the unmodified starch, with the slight differences likely due to some anhydroglucose units inhibiting the hydrolysis of the bonds. The digestibility was reported to be similar to other modified food starches.
In vivo studies
In a study with rats, starch sodium octenyl succinate (E1450) was fed to a group along with a basal diet, and their weight gains were similar to the group fed with sucrose. Another study with rats and dogs showed that they could metabolize OSA, but not to carbon dioxide and water. Instead, OSA was metabolized to tricarboxylic acid or was excreted unchanged. In a separate study, rats were given proprietary formulas containing OSA, and the total urinary excretion of OSA and its metabolites was approximately 35% to 12% and 19% to 2% of the oral dose in the respective groups.
Human studies
In simple terms, this discusses the results of two studies on the absorption and excretion of starch sodium octenyl succinate (E 1450) in infants and children. The studies found that between 10% and 25% of the ingested E 1450 was absorbed and excreted in urine, and that there were at least nine metabolites produced from the oxidation of E 1450. The studies also identified the molecular weight and mass fragmentation of these metabolites, and proposed that E 1450 is metabolised by a combination of x-, x-1 and b-oxidation steps, similar to valproic acid.
Acetylated oxidised starch (E 1451)
There was a lack of available data to draw from.
Starch aluminium octenyl succinate (E 1452)
There was a lack of available data to draw from.
Summary
Studies show that the digestibility of modified starches by digestive enzymes is slightly reduced or unchanged compared to unmodified starches. Different modifications of starch have varying effects on their digestibility. Starch sodium octenyl succinate was found to be excreted in urine, but the ADME database was considered sufficient to conclude that modified starches are significantly hydrolyzed by intestinal enzymes and fermented by gut bacteria in animals and humans. Fermentation of modified starches results in the production of short-chain fatty acids (SCFA), which are absorbed from the colon. The formation of SCFA from modified starches does not raise any safety concerns based on the available knowledge on their role as fermentation products of dietary fibers by the gut bacteria.