Barley Starch Research Articles

Characterization of ethanol fermentation waste and its application to lactic acid production by Lactobacillus paracasei

In this study, an ethanol fermentation waste (EFW) was characterized for use as an alternative to yeast extract for bulk fermentation processes. EFW generated from a commercial plant in which ethanol is produced from cassava/rice/wheat/barley starch mixtures using Saccharomyces cerevisiae was used for lactic acid production by Lactobacillus paracasei. The effects of temperature, pH, and duration on the autolysis of an ethanol fermentation broth (EFB) were also investigated. The distilled EFW (DEFW) contained significant amounts of soluble proteins (2.91g/l), nitrogen (0.47g/l), and amino acids (24.1mg/l). The autolysis of the EFB under optimum conditions released twice as much amino acids than in the DEFW. Batch fermentation in the DEFW increased the final lactic acid concentration, overall lactic acid productivity, and lactic acid yield on glucose by 17, 41, and 14%, respectively, in comparison with those from comparable fermentation in a lactobacillus growth medium (LGM) that contained 2g/l yeast extract. Furthermore, the overall lactic acid productivity in the autolyzed then distilled EFW (ADEFW) was 80 and 27% higher than in the LGM and DEFW, respectively.

Differential effects of genetically distinct mechanisms of elevating amylose on barley starch characteristics

The relationships between starch structure and functionality are important in underpinning the industrial and nutritional utilisation of starches. In this work, the relationships between the biosynthesis, structure, molecular organisation and functionality have been examined using a series of defined genotypes in barley with low (<20%), standard (20–30%), elevated (30–50%) and high (>50%) amylose starches. A range of techniques have been employed to determine starch physical features, higher order structure and functionality. The two genetic mechanisms for generating high amylose contents (down-regulation of branching enzymes and starch synthases, respectively) yielded starches with very different amylopectin structures but similar gelatinisation and viscosity properties driven by reduced granular order and increased amylose content. Principal components analysis (PCA) was used to elucidate the relationships between genotypes and starch molecular structure and functionality. Parameters associated with granule order (PC1) accounted for a large percentage of the variance (57%) and were closely related to amylose content. Parameters associated with amylopectin fine structure accounted for 18% of the variance but were less closely aligned to functionality parameters.

Dissolution and depolymerization of barley starch in selected ionic liquids

Polysaccharides like starch are poorly soluble in common solvents. However, certain ionic liquids (ILs) have been found to dissolve them, although some depolymerization happens during the dissolution. Dissolution and depolymerization of barley starch in ten ionic liquids have been studied with p-TsOH as a catalyst under controlled microwave heating. Dissolution time and the extent of the depolymerization of starch, determined by using HPLC-ELSD, were specific to each IL. Dialkylimidazolium halide ILs dissolved starch fast and depolymerized it substantially producing 79–100% water-soluble starch oligomers with the average molecular weight of 1000–2000Da. 1-Ethyl-3-methylimidazolium phosphate ([EMIM][Me2PO4]) and 2-hydroxyethylammonium formate ([NH3CH2CH2OH][HCOO]) dissolved starch slowly and depolymerized it least among the tested ILs. For the slow depolymerization of starch these ILs can be considered as suitable solvents for starch modifications where its depolymerization should be avoided.

Starch properties of malted barley in relation to real degree of fermentation

AbstractReal degree of fermentation (RDF) is an important measure of brewhouse performance in the production of beer. In this work, the relationship of RDF with malted barley starch properties was investigated. Starches were isolated from 25 malted barley samples and analyzed for molecular size distribution (by HPSEC), AP structural features (by high‐performance size exclusion chromatography with multi‐angle laser light scattering and RI detectors), and thermal properties (by DSC). Cluster analysis, analysis of variance, principal component analysis, bivariate correlation, and multiple linear regression analysis were used in establishing correlations. RDF, AM, and AP content were 74.0–80.1%, 25.2–34.4%, and 65.6–74.9%, respectively. Starch gelatinization enthalpy was 6.4–8.1 J/g, and onset gelatinization temperature was 58.5–64.3°C. AP and AM content had a positive and negative impact on RDF, respectively. The effect of thermal properties (starch gelatinization and AM‐lipid complex melting) on RDF was not clear. Starch properties explained up to 86% of RDF variance to indicate that other malted barley constituents and/or properties also contribute to cultivar variations in RDF.

Structural modification of waxy, regular, and high‐amylose maize and hulless barley starches on partial acid hydrolysis and their impact on physicochemical properties and chemical modification

AbstractWaxy (WX), regular (RA), and high‐amylose (HA) maize and hulless barley (HB) starches were subjected to partial acid hydrolysis with 1.0 and 2.2 N HCl for 30–240 min. In both starches, the extent of hydrolysis with 1.0 N HCl followed the order: HA&gt;WX&gt;RA, whereas with 2.2 N HCl, the order was: HA&gt;WX&gt;RA (maize) and WX&gt;HA&gt;RA (HB), respectively. The relative crystallinity increased (HA&gt;WX&gt;RA) and the X‐ray pattern remained unchanged, whereas the swelling factor decreased (WX&gt;RA&gt;HA in maize and WX&gt;HA&gt;RA in HB) at both acid concentrations. Starches hydrolyzed with 1.0 N HCl exhibited increased gelatinization temperatures (WX&gt;RA&gt;HA in maize, WX&gt;HA ∼ RA in HB), a narrower gelatinization temperature range (WX&gt;RA&gt;HA in maize, WX&gt;RA ∼ HA in HB) and a decreased gelatinization enthalpy (WX&gt;HA&gt;RA in maize and HB). Acid hydrolysis increased the accessibility of the phosphorylating reagent into the amorphous regions. The extent of phosphorylation was more pronounced (maize&gt;HB) in starches hydrolyzed with 1.0 N HCl for 60–90 min. The bound phosphorus content (BPC) followed the order: HA&gt;WX&gt;RA in maize and HB starches hydrolyzed with 1.0 N HCl for 240 min. In both starches, the extent of cationization was not influenced either by acid concentration or hydrolysis time. In general, acid hydrolysis significantly affected the reactivity of starch towards phosphorylation, where the optimum hydrolysis condition differed with starch source. The results would benefit the starch industry, since the amount of the phosphorylating reagent required for increasing thermal stability and/or freeze‐thaw stability could be decreased substantially, if starches are subjected to partial acid hydrolysis prior to derivatization.

Isolation and Characterization of Bacillus Subtilis KC3 for Amylolytic Activity

Microbial α-amylase is a highly demanded industrial enzyme with extensive commercial applications in various sectors. Studies were carried out with a bacterial strain producing extracellular α-amylase, isolated from rhizospheric soil of Euphorbia hirta. The isolate was gram positive, motile rod, bearing terminal endospore. It exhibited >98% similarity with the reference strains in the GenBank. The phylogenetic tree constructed on the basis of 16S rRNA gene sequences revealed that it clustered with the closest members of Bacillus subtilis and identified as Bacillus subtilis KC3. Furthermore, the effects of incubation period, temperature, pH, different carbon and nitrogen sources, metal salts and different substrate concentrations of the medium were optimized. The maximum enzyme production was found after 48 h (22.92 U/ml) of incubation at temperature 40 °C and pH 7. The optimal temperature and pH for enzyme activity were 50 °C and 6.5 respectively. Barley starch (27.27 U/ml) was observed to be the best inducer followed by corn starch (24.30 U/ml) and maltose (19.10 U/ml). The addition of glucose to the culture medium greatly reduced the synthesis of α-amylase (5.45 U/ml) which demonstrates that a classical glucose effect is operative in this organism. The effects of different metal ions (Ca 2+, Fe 2+ , Mg 2+ , Zn 2+ and Cu 2+ ) on amylolytic activity were investigated and it was found that 0.1% of Ca 2+ increased enzyme production (28.83U/ml), whereas other metal ions exhibited inhibitory effects. The enzyme production was maximum at 2% substrate (starch) concentration, which declined beyond it. These characteristics of Bacillus subtilis KC3, suggest that this is a promising isolate which merits further investigations for potential applications in various biotechnological processes.

Effects of Synchronization of Energy and Nitrogen Release in the Rumen on the Starch Disappearance in the Gastrointestinal Tract and Growth Performance of Hanwoo Steers

The objectives of experiments were to compare directly the effects of synchrony of slowly fermented (corn and corn gluten meal; C-CGM) and of rapidly fermented ingredients (barley and soybean meal; B-SBM) in the rumen on starch disappearances in gastrointestinal tracts (Experiment 1) and growth performance (Experiment 2) of Hanwoo steers in the feedlot barn. In experiment 1, four Hanwoo steers (<TEX>$288{\pm}21$</TEX> kg) fitted with ruminal and "T" shaped duodenal cannula were placed in one pen with Calan gate and assigned randomly to a duplicate <TEX>$2{\times}2$</TEX> Latin square design. In experiment 2, eight intact Hanwoo steers (<TEX>$311{\pm}8$</TEX> kg) were assigned randomly to one of two pens with Calan gate to evaluate the effect of the same diets as like in experiment 1 on growth performance. There were no differences in ruminal pH, ammonia and total VFA concentrations between treatments. Percentage of apparent ruminal starch disappearance was 33.3% unit lower (p<0.05) for steers fed C-CGM than for steers fed B-SBM diets and this difference resulted in 268% higher (p<0.05) in duodenal starch flows for steers fed C-CGM diet than for steers fed B-SMB diet. There was significant increase (p<0.05) in quantity (927 vs. 400 g/d) of corn starch digested post-ruminally compared to barley starch. However, percentage of starch apparently digested post-ruminally was 8% higher (p=0.1) in steers fed fast synchrony diet with B-SBM than in steers fed slow synchrony diets with C-CGM. The differences of percentage and amount of starch apparently digested post-ruminally between C-CGM and B-SBM diets did not affect rice straw DM intake, average daily gain (ADG) and feed efficiency. In conclusion, there is some uncertainty in regards to the relationship between site of starch digestion and DM intake, ADG, and feed efficiency in this study.

Extração de β-glucanas de cevada e caracterização parcial do amido residual

O objetivo do trabalho foi avaliar os parâmetros da extração de β-glucanas de cevada e caracterizar parcialmente o amido residual da extração. Foi desenvolvida metodologia para extração de β-glucanas de cevada sem degradação do amido, avaliando as variáveis pH e temperatura de extração. O percentual de β-glucanas extraída variou de 44,21 a 53,38%, sendo influenciado pela temperatura, e o de amido extraído variou de 65,98% a 77,54%, sendo influenciado pelo pH. O amido residual da extração de β-glucanas de cevada apresentou poder de inchamento e solubilidade de 8,54±0,29% e 6,04±0,073%, respectivamente. O amilograma de ARV desse amido apresentou viscosidade máxima de 164,67±1,30 RVU e quebra de viscosidade de 45,79±2,06 RVU. O espectro de infravermelho do amido residual é típico de amido de cevada nativo e semelhante ao de amidos isolados de milho, trigo e mandioca. De acordo com as micrografias eletrônicas de varredura da fração amido, foi possível visualizar uma mistura de grânulos grandes e lenticulares, com um diâmetro médio de 19,15µm e de granulos pequenos com forma esférica, de 4,78µm. As características demonstradas pelo amido residual da extração de β-glucanas de cevada sugerem sua viabilidade para utilização na indústria de alimentos.

Isolation and characterisation of starch from different barley and oat varieties

Starches were isolated from three oat (Dzoker, Zvolen and Sampionka) and three barley (Barun, Zlatko and Vanessa) cultivars. The gelatinisation and retrogradation characteristics, pasting properties, swelling power, and solubility of the isolated starches were analysed. The gelatinisation onset temperatures varied from 59.4&amp;deg;C to 61.4&amp;deg;C for the oat starches (OS), and from 58.4&amp;deg;C to 62.2&amp;deg;C for the barley starches (BS). BS displayed a higher retrogradation enthalpy (&amp;Delta;Hr) than OS after 7 and 14 days storage at 4&amp;deg;C. OS-Sampionka had the lowest one while BS-Vanessa had the highest &amp;Delta;Hr after 7 and 14 days of storage. Significant differences in pasting properties were observed between the OS and BS. OS showed higher values of maximum viscosity than BS and followed the order: OS-Dzoker &amp;gt; OS-Sampionka &amp;gt; OS-Zvolen &amp;gt; BS-Vanessa &amp;gt; BS-Zlatko &amp;gt; BS-Barun. The breakdown viscosities of BS were considerably lower than those of OS. OS had higher swelling power and solubility values than BS. The higher swelling and solubility values of the oat starches in conjunction with lower retrogradation suggest different applications of these starches. The results showed that, while the barley starches are suitable for such applications where high stability is needed during heating and shearing (low breakdown values), the oat starches have a great potential for the applications where high stability during storage is needed (low &amp;Delta;Hr values). In addition, the barley starches are suitable for those applications where high water binding is undesirable, while the oat starches are applicable where low amounts of starch need to bind high proportions of water

The barley amo1 locus is tightly linked to the starch synthase IIIa gene and negatively regulates expression of granule-bound starch synthetic genes.

In this study of barley starch synthesis, the interaction between mutations at the sex6 locus and the amo1 locus has been characterized. Four barley genotypes, the wild type, sex6, amo1, and the amo1sex6 double mutant, were generated by backcrossing the sex6 mutation present in Himalaya292 into the amo1 ‘high amylose Glacier’. The wild type, amo1, and sex6 genotypes gave starch phenotypes consistent with previous studies. However, the amo1sex6 double mutant yielded an unexpected phenotype, a significant increase in starch content relative to the sex6 phenotype. Amylose content (as a percentage of starch) was not increased above the level observed for the sex6 mutation alone; however, on a per seed basis, grain from lines containing the amo1 mutation (amo1 mutants and amo1sex6 double mutants) synthesize significantly more amylose than the wild-type lines and sex6 mutants. The level of granule-bound starch synthase I (GBSSI) protein in starch granules is increased in lines containing the amo1 mutation (amo1 and amo1sex6). In the amo1 genotype, starch synthase I (SSI), SSIIa, starch branching enzyme IIa (SBEIIa), and SBEIIb also markedly increased in the starch granules. Genetic mapping studies indicate that the ssIIIa gene is tightly linked to the amo1 locus, and the SSIIIa protein from the amo1 mutant has a leucine to arginine residue substitution in a conserved domain. Zymogram analysis indicates that the amo1 phenotype is not a consequence of total loss of enzymatic activity although it remains possible that the amo1 phenotype is underpinned by a more subtle change. It is therefore proposed that amo1 may be a negative regulator of other genes of starch synthesis.

Monitoring of barley starch amylolysis by gravitational field flow fractionation and MALDI‐TOF MS

In barley, starch occurs in the form of granules with bimodal size distribution. Enzymatic hydrolysis of the starch granule is one of the most important reactions occurring during malting and mashing. Previous studies revealed the discrepancies in the assumption that barley varieties with better malting qualities should have a higher A/B (large/small starch granules) ratio. This led us to focus our attention on detailed analysis of two barley varieties, Jersey and Tolar, both with high malting quality but significantly differing in A/B (1.28 and 0.66, respectively), were chosen for more detailed analysis in the actual work. In this study, the capacity of gravitational field flow fractionation (GFFF) to monitor amylolysis of the starch granules was investigated. Isolated starch granules from these two barley cultivars were treated with amylases. The changes in starch granule size and bimodal distribution were studied by GFFF. Simultaneously, free sugars released during enzymatic digestion were observed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The changes in the fractogram and in the mass spectra reflect a correlation with the progress of enzymatic hydrolysis. The results show the interest in utilization of GFFF as a simple and cheap method for monitoring changes in the distribution of the starch granule size during amylolysis.

Effects of barley β-glucan-enriched flour fractions on the glycaemic index of bread

The aim of this research was to evaluate β-glucan-enriched flours, obtained from barleys with either normal or waxy starch, for their effects on the glycaemic index (GI) and the quality of bread. Rheological results confirmed that when barley flour was included in the dough the overall quality of bread slightly worsened. However, positive consequences on glycaemia were obtained with the normal starch barley: the GI of all-wheat bread (82.8 ± 7.2) was significantly reduced (57.2 ± 7.9) when 40% of wheat flour was substituted with β-glucan-enriched barley flour (6.0% ± 0.1 β-glucan in the final flour blend). In contrast, this positive effect was significantly reduced (GI: 70.1 ± 9.1) when 40% of wheat flour was substituted with the β-glucan-enriched flour of a waxy barley (CDC Alamo; 6.6 ± 0.2 β-glucan in the final flour blend), suggesting that the ability of β-glucans to lower the GI was affected by the barley starch-type.

The cluster structure of barley amylopectins of different genetic backgrounds

The unit chains of amylopectin are organized into clusters. In this study, the cluster structure was analysed in detail in four different genotypes of barley, of which two possessed the amo1 genetic background. Amylose content of the barley starches differed from 0 to 32.6%. Isolated amylopectin was hydrolysed with α-amylase from Bacillus subtilis into domains, defined as groups of clusters, which were size-fractionated by methanol. The domain fractions were further treated with α-amylase to release single clusters. Amylopectin, domains and clusters were subsequently treated with phosphorylase and β-amylase to produce φ,β-limit dextrins and the detailed internal structures of these different structure levels were investigated. Analysis was performed with gel-permeation and anion-exchange chromatography. Equal amount of A-chains were detected in all barleys, but the distribution of B-chains differed. At least two types of domain structures were identified in all four barley varieties. Large domains were built up by large clusters and small domains by small clusters. In all four barley samples the number of long chains was small suggesting that shorter chains with a degree of polymerization of 25–35 also are involved in the interconnection of clusters. The cluster structure of the amylopectin correlated with the genetic background. The two barley samples with amo1 genetic background possessed a more dense structure. Internal chain lengths in these two barleys were shorter resulting in larger domains built up by larger clusters.

Mapping of quantitative trait loci controlling barley flour pasting properties

Pasting properties are important characteristics of barley starch from a processing standpoint. A shorter time to peak viscosity and lower pasting temperature are favorable to both malting and food processing. This study was conducted to identify quantitative trait loci (QTLs) determining pasting properties of barley flour using a doubled haploid population of 177 lines from the cross between six-rowed Yerong and two-rowed Franklin. Yerong is a feed barley with a longer time to peak viscosity and a higher pasting temperature than the other parent Franklin which is a malting barley. Field trials were conducted in three different sites/years. Seven different parameters representing the pasting properties were measured using a Rapid Visco-analyser (RVA). DH lines showed significant differences in all seven parameters in most of the sites/years. For example, the pasting temperature of different DH lines ranged from 73.8 to 89.5 in 2006/2007 MTP field trial. Twenty one QTLs were associated with flour pasting properties. These QTLs were distributed on 11 chromosome regions. Genetic variance explained by these QTLs varies from 4.4 to 15.2%. The most important QTLs controlling the time to peak viscosity and pasting temperature were located on 1H, 2H, 3H and 7H. Results showed that some of the pasting properties can be effectively selected by the combination of several molecular markers.

Application of aerosol‐spray deposition for determination of fine structure of barley starch using atomic force microscopy

AbstractStarch samples extracted from barley cultivars with varying AM concentrations were imaged by AFM using intermittent contact mode. Two different deposition methods were used: a simple solution drop and an aerosol spray deposition. Using the drop deposition method, starch appeared mainly as small particles and aggregated globules, with average heights of 1.8 ± 0.2, 2.7 ± 0.7, and 5.5 ± 1.0 nm, for starch solutions containing increased (38%), normal (25.8%), and undetectable (0%) AM, respectively. The aerosol spray deposition method allowed analysis of individual biopolymer chains of AM and biopolymer fibrils of AP. The image of normal starch showed individual AM chains with an average height of 0.8 ± 0.2 nm, and an average contour length of 178 ± 127 nm. For increased AM starch, the height of individual AM chains was similar to normal starch, but the average contour length was shorter (140 ± 70 nm). All barley starches showed fibril bundles of AP with average heights of 1.9 to 2.9 nm and lengths in the micron size range.

Recovery and Purity of Isolated Barley Starch and Protein as Affected by Fractionation Water Temperature

ABSTRACTWet fractionation of barley flours was conducted to identify appropriate fractionation water temperature considering the recovery and purity of starch and protein. In abraded hulless regular barley, yield of starch fraction, starch recovery, and purity of the protein fraction increased from 43.3 to 45.7%, from 61.7 to 64.8%, and from 37.6 to 65.2% when water temperature in fractionation was increased from 23 to 60°C. In abraded hulless waxy barley, recovery of starch with 40°C water was much greater (67.7%) than that at other temperatures (&lt;61.7%). Starch recovery and protein purity of regular barley cultivars were higher than those of waxy barley cultivars with fractionation water of 60°C. In whole hulless barley flours fractionated with 60°C water, waxy barley flours showed similar to or higher protein purity (44.8–48.9%) than regular barley flours (42.8– 44.6%), while regular barley flours exhibited higher starch recovery (&gt;60.6%) than waxy barley flours (&lt;57.3%). The purity of isolated starch was &gt;97.7%, regardless of water temperature and barley type. Considering yield and recovery of the isolated starch, and purity of the isolated protein, 60°C water for hulless regular barley and 40°C for hulless waxy barley seem to be appropriate for fractionation of barley flour for isolation of starch and protein.

Impact of Micronization on Rapidly Digestible, Slowly Digestible, and Resistant Starch Concentrations in Normal, High-Amylose, and Waxy Barley

This study determined the effect of micronization (high intensity infrared heating) on the concentrations of rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) in normal barley (NB), high-amylose barley (HAB), and waxy barley (WB). The gelatinized starch contents and the thermal properties of the micronized samples also were determined. Samples of each barley type were tempered to each of three moisture contents (approximately 17, 31, or 41%), and then each tempered sample was micronized to each of three surface temperatures (100, 120, or 140 degrees C). Micronized barley samples were substantially lower in RS and in SDS and, therefore, higher in RDS than corresponding unprocessed samples. In general, higher concentrations of RDS and of gelatinized starch were associated with higher initial moisture contents and higher surface temperatures. The lowest concentrations of RS were observed in micronized WB samples. Similar concentrations of RS were observed in corresponding NB and HAB samples. Micronization resulted in slight increases in the onset (To), peak (Tp), and completion (Tc) gelatinization temperatures and in substantial reductions in the gelatinization enthalpy (DeltaH), the latter reflecting the levels of gelatinized starch in micronized samples, particularly in samples micronized at higher moisture contents and to higher surface temperatures. Endothermic transitions were evident only in samples tempered to 17% moisture or 31% moisture (surface temperature of 100 degrees C only).

Effect of reagent type on the acetylation of barley and maize starches

AbstractThe objective of this work was to study the effect of reagent type on properties of acetylated barley starch (BS) and maize starch (MS) after modification with acetic anhydride (AA) and vinyl acetate (VA) at similar molar concentration for mole of glucose of both reagents. Degree of substitution (DS), morphological characteristics and granule size distribution, gelatinization and retrogradation, pasting properties, and X‐ray diffraction pattern were evaluated. Acetylation disturbs the short and long range order, and the effect was higher with AA than VA, and for BS than MS. This is due to the higher DS determined in AA–BS. In the pasting profile, acetylated starch showed the maximum peak viscosity at lower temperature, this effect was strongest for BS and anhydride acetic‐acetylation. Differential scanning calorimetry showed decrease in gelatinization parameters in acetylated starches (temperatures and enthalpy), and retrogradation was suppressed by acetylation. This effect was stronger in starches acetylated with AA despite their higher DS. This pattern can be explained from the occurrence of surface effects in acetylation with AA.

Effects of starch and protein sources on starch disappearance in the gastrointestinal tract of Hanwoo (Korean native) steers

Hanwoo (Korean native) steers (274.8 +/- 4.6 kg) with ruminal and duodenal cannulae were used in a 4 x 4 Latin square design experiment to examine the effects of dietary treatments on starch disappearance in the gastrointestinal tract. Dietary treatments consisted of concentrate that were based on ground corn with soybean meal (C-SBM), ground corn with corn gluten meal (C-CGM), ground barley with soybean meal (B-SBM) and ground barley with corn gluten meal (B-CGM). Although the intakes of starch and protein for steers fed experimental diets were different, it did not change ruminal pH and total volatile fatty acid concentrations. Average duodenal CP flow and quantity of CP apparently digested post-ruminally was higher (P = 0.001) for CGM-based diets than SBM-based diets. There were increases in quantity (P < 0.001) and percentage (P < 0.001) of corn starch digested post-ruminally compared to barley starch. Synchronized diets showed higher percentages (P = 0.03) of starch apparently digested post-ruminally than asynchronization. Hanwoo steers fed a corn-based diet with a large quantity of starch reaching the duodenum and fed C-CGM supplying great amounts of protein to the small intestine may have contributed to increased post-ruminal starch digestion.

Effect of low and high acetylation degree in the morphological, physicochemical and structural characteristics of barley starch

Barley starch was acetylated at two levels (low degree: LD (0.9), and high degree: HD (2.7)) substitution and the morphological, physicochemical and structural of the resultant acetylated barley starch were determined. The acetylated barley starches presented the signal at 1226 cm −1 that corresponds to the C–O stretching of acetyl groups. The morphological study showed fusion of starch granules in the acetylated starch with HD. This effect was evident in the pasting test, because the viscoamylograph profile of HD starch showed the absence in peak viscosity, viscosity breakdown and viscosity setback. The peak gelatinization was similar for native and LD and decrease in the HD acetylated starch. The gelatinization enthalpy value showed difference among the samples, indicating that the loss of the ordered double helices more than the crystallinity loss was higher in the HD acetylated barley starch. In the retrogradation test, acetylation affected both retrogradation and enthalpy value, because acetylated barley starch with HD substitution at three storage days had 3.2 j/g and with LD 4.8 j/g. The molecular weight and z-average radius of gyration values decreased due to the acetylation process, indicating depolymerization of starch components as it was evidenced by the increase in short chains level in the acetylated samples.