Influence of acetylation on physicochemical, functional and thermal properties of potato and cassava starches

Starches were isolated from cassava (Manihot esculenta) and potato (Solanum tuberosum) tubers. They were further modified by acetylation. The physicochemical, functional and thermal properties of native and modified starches, prepared using acetic anhydride at different times (10 and 20 min) were compared. Potato starch (Sipiera/20) showed higher acetyl percentage and degree of substitution values than cassava (2425/20) starch when acetylated for 20 min. Proximate analysis revealed that the acetylated starches retained more moisture than the native ones. Above 75 °C, acetylation improved the water binding capacity of the native cassava starch; the same trend was observed for potato starch from 60 to 90 °C after acetylation. The X-ray powder diffraction patterns derived from acetylated potato starches were similar to its native form, which was expected as B-type pattern; the same trend was observed for modified cassava starch. However the modified starches showed increased crystalline index.     

Physico-chemical properties of potato starches

Starches were isolated and characterised from 10 potato cultivars grown under the same conditions (with a commercial starch for reference). The chemical composition revealed some differences amongst the starches with protein ranging from 0.30% to 0.34%, amylose 25.2% to 29.1% and phosphorus 52.6–66.2 mg 100 g⁻¹. High performance size-exclusion chromatography (HPSEC) fractionation of isoamylase debranched amylopectin showed that the amylopectin molecules were less branched and consisted of more B1, but less A-chains, than cereal starches. Gelatinisation onset (T_o), peak (T_p) and conclusion (T_c) temperatures of the native potato starches ranged from 58.7 to 62.5 °C, 62.5 to 66.1 °C and 68.7 to 72.3 °C, respectively, whilst the gelatinisation enthalpies ranged from 15.1 to 18.4 J g⁻¹. The gelatinisation temperatures of the starches increased in common with the amounts of short and intermediate sized amylopectin chains. The ¹³C magic angle spinning nuclear magnetic resonance (¹³C CP-MAS NMR) and wide angle X-ray diffraction (XRD) data (30.6% ± 0.22% crystallinity on average) showed little variance amongst the samples. Particle sizing results, however, revealed more variance (20.6–30.9 μm mean diameter). Overall, these data reveal the subtleties of cultivar specific variation against a background of constant environmental conditions.     

Influence of moisture content on the degradation of waxy and normal corn starches acid-treated in methanol

Waxy and normal corn starches with different moisture contents, 5.1-16.9% and 4.8-15.9%, respectively, were prepared and treated in methanol containing 0.36% HCl at 45 °C for 1 h. Recovery of all the treated starches was found to be above 90%. Peak viscosity, gelatinization temperature and enthalpy change of gelatinization of waxy and normal corn starches decreased after treatment and this decrement was found to be more in treated starches having lower initial moisture content. The weight-average degree of polymerization and chain length (CL) of waxy and normal corn starches decreased upon acid-methanol treatment. The decrement ratio of molecular weight of modified starches was found to be negatively correlated with the initial moisture content of the starches. The decrement ratio of normal corn starch was higher than waxy corn starch with similar moisture content of starch. The content and CL of long chain fraction of amylopectin for waxy corn starch slightly decreased after treatment, while no obvious trend was found among starches with different moisture contents. CL of amylose for acid-methanol-treated normal corn starch decreased and this change was found to be higher in starches with lower initial moisture contents. Results demonstrated that the initial moisture content of starch granules strongly influenced the functional properties and degradation of starch treated by acid in methanol.     

Physicochemical properties of starches obtained from Polish potato cultivars

Selected physicochemical, thermal, and rheological properties of starches isolated from new Polish potato varieties were determined. The starches contained 25.7–30.0 g/100 g d.m. of amylose and 59.5–90.2 mg/100 g d.m. of phosphorus. Gelatinization temperatures were 62.6–64.0, 68.9–69.9, and 73.6–77.0°C for T_O, T_P, and T_E, respectively, whilst enthalpy of gelatinization amounted to 11.1–15.3 J/g. The retrogradation degree of starch was from 52.90 to 78.53%. Pasting curves showed significant differences between the starches. Peak viscosity and final viscosity ranges were 2035–4458 and 1931–2985 mPa · s, respectively. Starch pastes exhibited non‐Newtonian, shear thinning, and thixotropic behavior. After cooling they demonstrated diversified viscoelastic properties, however, all of them were classified as weak gels. Significant linear correlations among selected rheological parameters and amylose and phosphorus content were found. Results of principal component analysis demonstrated an ability to differentiate the starches isolated from different potato varieties.     

Properties of enzyme modified corn, rice and tapioca starches

Corn, rice and tapioca starches were partially hydrolyzed by treating the starch dispersions with heat stable α-amylase. Dextrose equivalent (DE) of 8–12 was achieved by hydrolyzing the starch samples (10–20% w/v) for 30 min at 90 ± 2 °C. Scanning electron micrographs showed that starch granules had broken down to smaller particles. High performance liquid chromatography with refractive index detection indicated that oligosaccharides with broad molecular weight distributions are present in the reaction products. Hydrolyzed starch dispersions were analyzed for their rheological properties. The storage modulus values (G′) for 20% solid containing slurries were 7373 and 1470 Pa for untreated and enzyme treated samples, respectively, indicating a marked decrease in solid properties due to enzyme action. The complex viscosities (η^*) for native corn starch and hydrolyzed corn starch were 8243 and 1637 Pas, respectively, which indicate that the enzyme treatment decreases the overall resistance of the sample to flow such that the product can spread easily. Further 13C CP/MAS NMR and FTIR studies revealed the loss of ordered structures in the enzyme modified starches. Free flowing fat substitute in the form of fine powder was prepared by spray drying the hydrolyzed starch slurry.     

Correlation between the compositional and pasting properties of various potato starches

Multiple linear regression equations were used to develop the correlation between the compositional and rapid visco-analysis (RVA) pasting properties of various potato starches. The amylose of potato starches had a negative correlation with the peak viscosity (PV) and breakdown (BD) and a positive correlation with the setback viscosity (SV) and peak viscosity temperature (PVT). By contrast, phosphorus had a positive correlation with PV, BD, and SV and a negative correlation with PVT. In addition, the median granule size had a positive correlation with PV and BD. By contrast, a negative correlation of the median granule size was observed with SV and PVT. The correlation coefficients of amylose–phosphorus, amylose–granule size, and phosphorus–granule size interactions indicated that amylose had more influence than had phosphorus or had the median granule size on PV and BD. Furthermore, amylose had a greater influence than had the granule size on SV and PVT. Similarly, amylose had more influence than had phosphorus or had the median granule size on PVT. However, the correlation developed in this study was useful for predicting the influence of a specific component and the compositional interaction on the RVA pasting properties.     

Some properties of corn starches II: Physicochemical,gelatinization, retrogradation,pasting and gel textural properties

The physicochemical, thermal, pasting and gel textural properties of corn starches from different corn varieties (African Tall, Ageti, Early Composite, Girja, Navjot, Parbhat, Partap, Pb Sathi and Vijay) were studied. Amylose content and swelling power of corn starches ranged from 16.9% to 21.3% and 13.7 to 20.7 g/g, respectively. The enthalpy of gelatinization (ΔH_gel) and percentage of retrogradation (%R) for various corn starches ranged from 11.2 to 12.7 J/g and 37.6% to 56.5%, respectively. The range for peak viscosity among different varieties was between 804 and 1252 cP. The hardness of starch gels ranged from 21.5 to 32.3 g. African Tall and Early Composite showed higher swelling power, peak, trough, breakdown, final and setback viscosity, and lower ΔH_gel and range of gelatinization. Pearson correlations among various properties of starches were observed. Gelatinization onset temperature (T_o) was negatively correlated to peak-, breakdown-, final- and setback viscosity (r = −0.809, −0.774, −0.721 and −0.686, respectively, p < 0.01) and positively correlated to pasting temperature (r = 0.657, p < 0.01). ΔH_gel was observed to be positively correlated with T_o, peak gelatinization temperature and (T_p) and gelatinization conclusion temperature T_c (r = 0.900, 0.902 and 0.828, respectively, p < 0.01) whereas, it was negatively correlated to peak- and breakdown- (r = −0.743 and −0.733, respectively, p < 0.01), final- and setback viscosity (r = −0.623 and −0.611, respectively, p < 0.05). Amylose was positively correlated to hardness (r = 0.511, p < 0.05) and gumminess (r = 0.792, p < 0.01) of starch gels.     

Impacts of acid-methanol treatment and annealing on the enzymatic resistance of corn starches

Normal corn, Hylon V and Hylon VII starches were acid-methanol-treated at 25 °C for 1–30 days in methanol containing 0.36% HCl, and then annealing at 50 °C for 72 h in excess water. The rapid digestible starch (RDS), slow digestible starch (SDS) and resistant starch (RS) contents of starch before and after treatments were determined. The molecular structure, thermal properties, double helix content and relative crystallinity of starch were observed for elucidating the impacts of acid-methanol treatment and annealing, as well as the molecular structure, on the enzymatic resistance of starch. Results showed that the weight-average degree of polymerization of acid-methanol-treated corn starches ranged from 884 × 10³ to 404, 778 × 10³ to 299 and 337 × 10³ to 250 anhydrous glucose units for normal corn, Hylon V and Hylon VII starches, respectively. Annealing increased the RS content of starch, and the increment of RS increased with decreasing molecular size of starch. Furthermore, the change in RS content after treatments depended on the content and weight-average chain length of amylose fraction of starch. The RS content of starch after treatments increased from 19.2 to 56.2%, 69.9 to 86.1%, and 73.1 to 89.1% for normal corn, Hylon V and Hylon VII starches, respectively. The gelatinization peak temperature and double helix content of starch increased after acid-methanol treatment or annealing. Results demonstrate that the degradation of starch, causing by acid-methanol treatment, enhances the mobility and realignment of starch chains in molecules during treatments and further increases the enzymatic resistance of starch granules.     

A comparison of native and oxidized normal and waxy corn starches: Physicochemical, thermal, morphological and pasting properties

The effect of sodium hypochlorite on the physicochemical and functional properties of normal and waxy corn starches was investigated in this study. It was found that both carboxyl and carbonyl contents of oxidized starches from normal corn were higher than those of waxy corn. The introduction of carboxyl and carbonyl groups resulted in lower amylose content and swelling power. Both amylose and amylopectin were oxidized and degraded during oxidation but amylose was more susceptible to oxidation. Studies conducted on paste clarity revealed that the percentage transmittance increased after oxidation. The morphology of the starches was not altered after oxidation. Thermal properties measured by differential scanning calorimeter, showed that oxidation reduced transition temperatures (onset temperature, T_o; peak temperature, T_p; and conclusion temperature, T_c), gelatinization and retrogradation enthalpies of both normal and waxy corn starches. The retrogradation tendency was reduced after oxidation both in normal and waxy corn starches. Oxidation produced waxy starch with significantly higher peak (P_V), trough (T_V), breakdown (B_V), final (F_V), and setback viscosity (S_V) as demonstrated by using a rapid visco analyzer. Oxidation reduced the pasting temperature of both normal and waxy corn starches. Also, the principal component analysis (PCA) study was conducted to find the overall variations among the oxidized starches studied. Together, the first two components represent 88.7 g/100 g of the total variability.     

Studies on noodle quality of potato and rice starches and their blends in relation to their physicochemical, pasting and gel textural properties

The physicochemical, pasting, and gel textural properties of potato and rice starches and their blends were studied in relation to their noodle making performance. Amylose content, swelling power and solubility values of potato starch were significantly (P ≤ 0.05) higher than for rice starch. Pasting properties showed higher peak, final and setback viscosity for potato starch as compared to rice starch. Texture profile analysis revealed that potato starch gel had higher hardness, cohesiveness and chewiness as compared to rice starch gel. Potato starch noodles showed higher cooked weight and cooking loss and were scored higher by sensory panellists especially with respect to transparency and slipperiness. On the other hand, rice starch noodles were more firm with lower cooking loss. Addition of potato starch to rice starch significantly (P ≤ 0.05) affected the noodle characteristics. Among the starch blends studied, blending of potato and rice starch in the ratio of 1:1 resulted in good quality noodles in terms of their lower cooking time, higher cooked weight, transparency and slipperiness. The results revealed the possibility of blending of potato starch with rice starch in equal proportions to produce noodles of acceptable quality.     

Physicochemical properties of potato and cassava starches and their mutants in relation to their structural properties

Physicochemical properties [swelling power (SP), pasting behaviour and retrogradation] of five wild type (wt), five amylose free (amf), four high-amylose (ha) potato starches (ps) and one wt and amf cassava starch (cs) were investigated. While swelling of wtps occurred in two phases, amfps showed a very fast swelling and no gel of swollen granules was observed at higher temperatures (>90 °C). Haps underwent only restricted swelling. SP of cassava starches were lower than those of potato starches. Wtps leached mainly amylose (AM) during heating at low temperatures. Molecules of higher molecular weight (MW) leached out at higher temperatures. Longer amylopectin (AP) chains [degree of polymerisation (DP) > 18] inhibited swelling while short chains (DP < 14) favoured swelling. Starch pasting behaviour of 5.0 and 8.0% starch suspensions was studied using Rapid Visco Analyser (RVA). For 5.0% suspensions, increased levels of high-MW AP and decreased levels of AM molecules led to higher peak viscosity. Longer AP chains (DP > 18) depressed peak viscosity, while short chains (DP < 14) increased peak viscosity for both concentrations. At 8.0%, peak viscosity increased with starch granule size. After 1 day of storage of gelatinised starch suspensions, wtps and especially amfps showed only limited AP retrogradation. In contrast, the high enthalpies of retrograded AP (ΔH_retro) and peak and conclusion temperatures of retrogradation (T_p,retro and T_c,retro) of haps suggested partial cocrystallisation between AM and AP. Chains with DP 18–25 seemed to be more liable to AP retrogradation. Wtcs and amfcs did not retrograde at room temperature.     

Experimental design to optimization of beta cyclodextrin production from ungelatinized sago starch

The aim of this study is to produce beta cyclodextrin (β-CD) from ungelatinized, but annealed (65 °C) sago starch using cyclodextrin glucosyltransferase (CGTase). The optimization processes were conducted at three stages using Response Surface Methodology. Preliminary data have shown that the three (3) highest points for each of the studied parameters were pH, concentration of sago starch and enzyme, and also agitation. In the second stage, two level full factorial design (2ⁿ FFD) was applied to determine the significant parameters affecting the production of β-cyclodextrin. Statistical analyses showed that pH, enzyme and sago starch concentration were the significant parameters. The final stage of optimization involved the use of Central Composite Design to determine and predict the optimum yield of β-cyclodextrin. The optimum condition for production cyclodextrin was at pH 8.62 (Glycine–NaOH buffer 0.05 M), 0.65% v/v sago starch and 15% w/v enzyme concentration, where 8.43 g β-cyclodextrin/L was produced after 4 h of reaction.     

Thermal,rheological, and mechanical properties of normal corn and potato starch blends

Native corn and potato starches were mixed in different proportions. Blends presented similar values to potato starch at onset temperature and at ending temperature to corn starch. CS20PS80 blend had the highest values for hardness between blends due to the formation of a three-dimensional network with corn starch granules that act as composite material. Some blends exhibited higher recovery viscosity than native starches, possibly due to interactions. Gelatinization temperature, swelling power, phosphorous content, granule size, and x-ray pattern played an important role in the resulting properties, however, the amylose content did not show influence due to both starches having a similar content.     

A comparison of native and acid thinned normal and waxy corn starches: Physicochemical, thermal, morphological and pasting properties

The starches isolated from normal and waxy corn varieties were hydrolyzed with hydrochloric acid (0.14 mol equivalent/L) and evaluated for physicochemical and functional properties. Acid thinning decreased the amylose content and swelling power but increased the solubility. The light transmittance of acid thinned (AT) starch pastes was higher than those of their native starches after similar storage intervals. The scanning electron microscopic observation demonstrated that the acid thinning did not cause any disruption of the granular crystalline structure. Native normal corn starches showed lower onset temperature (T_o) and peak temperature (T_p) as compared to their counterpart AT starches, whereas the reverse was observed for waxy corn starch. Enthalpy of gelatinization (ΔH_gel) was lower in AT normal and waxy starches as compared to their native starches. The percentage of retrogradation (%R) was significantly higher for native corn starches as compared to their AT starches. A significant reduction in peak—(P_V), trough—(T_V), breakdown—(B_V), final—(F_V), and setback viscosity (S_V) was observed by acid thinning, and the reduction was more pronounced in AT waxy starches. Among AT starches, AT waxy starch showed the lowest values of P_V, T_V, B_V, F_V and S_V.     

Structural properties and gelatinisation characteristics of potato and cassava starches and mutants thereof

The molecular size of amylopectin (AP) and amylose (AM), AP chain length distribution, crystallinity and granular structure (morphology and granule size distribution) of five wild type potato starches (wtps), five AM free potato starches (amfps), four high-AM potato starches (haps), one wild type cassava starch (wtcs) and one AM free cassava starch (amfcs) were investigated and related to their gelatinisation characteristics. Starches with higher levels of short chains [degree of polymerisation (DP) 6–9 and DP 10–14)] had lower gelatinisation onset (T_o), peak (T_p) and conclusion (T_c) temperatures, whereas higher contents of longer chains (DP 18–25 and DP 25–80) led to higher gelatinisation temperatures. Gelatinisation enthalpies (ΔH) increased with degree of crystallinity. The granules of wtps were larger than those of amfps and haps, respectively. No differences in morphology were observed between wtps and amfps granules, but the haps granules had more irregular surfaces and showed multi-lobed granules.     

In vitro amylolytic degradation of natural and graft copolymerised cassava and potato starches

 Various enzymatic hydrolyses to maximise degradation of the starch moiety of grafted starch (starch–g-polyacrylonitrile) were tried. The percentage of α- and β-amylolyses of grafted starch were 55 and 50 compared to 80 and 70 respectively for natural starches. Sequential degradation with α-amylase and glucoamylase of grafted starch showed 70% hydrolysis. The maltooligosaccharide profile by HPLC of the hydrolysates of grafted starch showed oligomers up to a degree of polymerisation (DP) 3, whereas the natural starch hydrolysates showed up to DP 7. The percentage hydrolysis, as well as the enzyme degradation profile, remained similar for both potato and cassava starches. Further treatment of the grafted starch hydrolysates with Bacillus cereus cells showed the presence of very low molecular weight polyacrylonitrile chains grafted onto maltooligosaccharides. The size exclusion chromatography analysis of grafted starch indicated the amylose component of starch that undergoes graft copolymerisation. Received: 30 December 1999     

RVA study of mixtures of wheat flour and potato starches with different phosphorus contents

A rapid visco analysis (RVA) system was used to study the pasting properties of mixtures of wheat flour and potato starches with high phosphorus (HPS), medium phosphorus (MPS) and low phosphorus (LPS) contents, different granule sizes and different amylose contents. The peak viscosities, trough and breakdown, final viscosities, setback viscosities and peak times of control potato starches were found to be higher than those of wheat flour. The peak viscosities were increased significantly with increase of potato starches in the mixtures. Thus, the peak times decreased with increase of potato starch in the mixtures. The breakdown viscosities increased significantly with increase of potato starches in the mixtures and the values were found to be higher in HPS-wheat, followed by MPS-wheat and LPS-wheat mixtures. The final viscosities of HPS-wheat mixtures were highest, followed by MPS-wheat and LPS-wheat mixtures. The setback viscosities of LPS-wheat were significantly higher than those of MPS-wheat and HPS-wheat mixtures at 30 to 50% potato.     

Effects of plasticizers on thermal properties and heat sealability of sago starch films

Sago starch films were plasticized with sorbitol, glycerol, or a combination of sorbitol/glycerol (1:1, 1:3, and 3:1 ratios) and the effects on the thermal properties and heat sealability of the films were investigated. Films were sealed with an impulse heat sealer at a dwell time of 1 s and temperature of 110 ± 10 °C. Thermal properties of the films (determined using a differential scanning calorimeter) showed that onset temperatures (T_o) of sorbitol-plasticized films were significantly lower than those of glycerol-plasticized films. All films were heat sealable, but sorbitol-plasticized films exhibited better heat sealability than did the glycerol type. The highest seal strength was obtained with a 3:1 combination of sorbitol/glycerol. In summary, the type of plasticizer governed the heat sealability as well as the seal strength of starch films.     

Physicochemical properties of five cocoyam (Colocasia esculenta and Xanthosoma sagittifolium) starches

Physicochemical properties of starches of five cocoyam cultivars were evaluated. CIE L^*, a^*, b^* colour parameters of corm and starches were measured. Amylose, pasting and functional properties of the starches were investigated using colourimetric, Rapid Visco-Analyser and standard methods respectively. Cocoyam starches were white in colour as shown by L^* (84.83–88.65), a^* (+0.01–+1.19), and b^* (+15.33–+16.54) values. Starch granule sizes varied significantly in length (6.47–13.63 μm) and width (5.36–8.45 μm), while amylose content ranged from 11.55% (NCe002) to 33.77% (NXs001). Peak (49.09–141.96 RVU), breakdown (49.09–141.96 RVU), final (189.79–327.42 RVU) viscosities, pasting temperature (84.53–88.75 °C) and time (4.55–4.97 min) varied significantly (p < 0.05) among cultivars. Also, water absorption capacity (21–36%), pH (4.8–5.3), gelling point (60.5–69.5 °C), foam capacity (4.46–18.28%), bulk density (0.14–1.15 g/mL) and swelling power (2.31–10.09) varied significantly (p < 0.05) among the cultivars. Average yield of the starches varied significantly from 10.03 (NCe001) to 18.61% (NXs001).