Structural,thermal and viscoelastic characteristics of starches separated from normal,sugary and waxy maize

Starches separated from five types of maize (two normal, one sugary and two waxy) were investigated for physicochemical, thermal, amylopectin structure and viscoelastic properties. Kisan and Paras were normal maize while Parbhat and LM-6 were waxy maize type. Apparent amylose content of normal and sugary maize was 29.5–32.6 and 41.0%, respectively. Swelling power of normal, sugary and waxy maize starches was 11.6–15.2, 7.8 and 30.2–39.2 (g/g), respectively. X-ray diffraction of maize starches indicated typical A-pattern. Maize starch showed a single broad peak at 2θ=23.2° and a dual peak 2θ=17°–18.1, respectively. Waxy maize starches showed the presence of greater crystallinity than other starches while sugary maize starch showed the presence of lower crystallinity and a large amount of amylose–lipid complex. Intrinsic viscosity [η] of starches in 90% DMSO at 25 °C was 79.7–119.5 ml g⁻¹ for normal, 70.5 ml g⁻¹ for sugary and 107.2–118.1 ml g⁻¹ for waxy starches. Branch chain–length distribution of amylopectin revealed that the apparent amylose, long side chain- and short side chain-amylopectin proportion ranged between 0.0–41%, 13.4–31.5% and 41.5–66.8%, respectively, among the various maize starches. Maize sugary showed the highest apparent amylose content and the least amount of short- and long-side chains of amylopectin. LM-6 and Parbhat showed higher proportion of both long- and short-chain amylopectin as compared to other starches. Distribution of α-1, 4-chains of amylopectin (short-/long-chain) ranged between 2.1 and 3.4, the least for LM-6 and the highest for Paras starch. The transition temperatures (T_o–T_c) ranged between 60.5 and 76.1 °C for sugary, 63.5–76.3 °C for normal and 64.4–81.3 °C for waxy maize starch. The enthalpy of gelatinization (ΔH_gel) of sugary, normal and waxy maize starches was 2.47, 3.7–4.75 and 4.15–5.4 J/g, respectively. Normal and sugary maize starches showed higher G′ and G″ than waxy type starches. The change in the moduli during cooling and reheating of pastes cooked at different temperatures revealed low disintegration of granular structure in starch with higher amylose and amylose–lipid complex as well as low crystallinity. The changes in moduli during 10 h at 10 °C revealed highest retrogradation in maize sugary followed by Paras and Kisan starch.     

Effect of annealing on the structure and physicochemical properties of barley starches of varying amylose content

Starch from normal (CDC McGwire, SR 93102), waxy (CDC Fibar, HB 364), and High amylose (SB 94897, SB 94893) hull-less barley cultivars was isolated and its structure, morphology, and properties were studied before and after one-step annealing (50 °C for 72 h at a moisture content of 75%). The amylopectin structure of all starches was nearly identical. The X-ray pattern of CDC Fibar, HB 364, and CDC McGwire starches was of the ‘A’-type. Whereas, SR 93102, SB 94897, and SB 94893 starches exhibited a mixed ‘A + B’-type pattern. The relative crystallinity (RC), swelling factor (SF), amylose leaching (AML), gelatinization temperature range (GTR), enthalpy of gelatinization (ΔH), amylose–lipid complex melting temperature (Tp_CX) and the enthalpy of melting of the amylose–lipid complex (ΔH_CX) ranged from, 37.0% to 44.3%, 41.0–54.2% (at 90 °C), 4.0–31.0% (at 90 °C), 11.4–22.5 °C, 6.0–13.0 J/g, 84.9–89.1 °C and 0.4–1.8 J/g, respectively. The RC of CDC Fibar, HB 364, SR 93102 and CDC McGwire starches increased on annealing. Whereas, it remained unchanged in SB 94897 and SB 94893 starches. The ‘A’-type X-ray pattern of CDC Fibar, HB 364, and CDC McGwire starches remained unchanged on annealing. However, the ‘A + B’-type X-ray pattern of SR 93102, SB 94897 and SB 94893 starches resembled more closely the ‘A’-type pattern on annealing. In all starches, the X-ray intensity of the V-amylose–lipid complex peak increased on annealing. Annealing increased the gelatinization transition temperatures and decreased the GTR in all starches. The ΔH of SB 94893 starch increased on annealing, whereas it remained unchanged in the other starches. Tp_CX of SR 93102 and SB 94897 remained unchanged on annealing, whereas Tp_CX of CDC McGwire increased slightly. ΔH_CX of native and annealed CDC McGwire, SR 93102 and SB 94897 were similar. Tp_CX and ΔH_CX were not detectable in annealed SB 94893 starch. In all starches, SF decreased on annealing. Annealing decreased AML in SR 93102, SB 94897 and SB 94893 starches in the temperature range of 50–90 °C, but increased AML in HB 364 and CDC McGwire starches at higher temperatures. The effect of annealing on acid hydrolysis was marginal.     

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.     

Physical and structural changes induced by high pressure on corn starch,rice flour and waxy rice flour

The impact of high pressure (HP) processing on corn starch, rice flour and waxy rice flour was investigated as a function of pressure level (400 MPa; 600 MPa), pressure holding time (5 min; 10 min), and temperature (20 °C; 40 °C). Samples were pre-conditioned (final moisture level: 40 g/100 g) before HP treatments. Both the HP treated and the untreated raw materials were evaluated for pasting properties and solvent retention capacity, and investigated by differential scanning calorimetry, X-ray diffractometry and environmental scanning electron microscopy. Different pasting behaviors and solvent retention capacities were evidenced according to the applied pressure. Corn starch presented a slower gelatinization trend when treated at 600 MPa. Corn starch and rice flour treated at 600 MPa showed a higher retention capacity of carbonate and lactic acid solvents, respectively. Differential scanning calorimetry and environmental scanning electron microscopy investigations highlighted that HP affected the starch structure of rice flour and corn starch. Few variations were evidenced in waxy rice flour. These results can assist in advancing the HP processing knowledge, as the possibility to successfully process raw samples in a very high sample-to-water concentration level was evidenced.Industrial relevanceThis work investigates the effect of high pressure as a potential technique to modify the processing characteristics of starchy materials without using high temperature. In this case the starches were processed in the powder form - and not as a slurry as in previously reported studies - showing the flexibility of the HP treatment. The relevance for industrial application is the possibility to change the structure of flour starches, and thus modifying the processability of the mentioned products.     

Starch from hull-less barley: II. Thermal,rheological and acid hydrolysis characteristics

Gelatinization, granular swelling, amylose leaching, viscosity and acid susceptibility characteristics of starches isolated from 10 hull-less barley (HB) genotypes [zero amylose (CDC Alamo), waxy (CDC candle, SB 94794, SB 94912, and SB 94917), normal amylose (Phoenix, CDC Dawn, SR 93102, and SB 94860) and high amylose (SB 94893 and SB 94897)] were monitored by differential scanning calorimetry (DSC), swelling power (SP), solubility, Brabender viscoamylography, and reaction with 2.2 N HCl (at 35 °C), respectively. DSC data showed that T_o, T_p, T_c, T_c–T_o, and ΔH ranged from 50.1–56.1, 58.1–64.5, 71.0–75.8, 17.9–24.0 °C and 9.6–14.2 J/g of amylopectin, respectively. In compound waxy (SB 94917) and compound normal (SR 93102 and SB 94860) starches, T_o and T_c–T_o were lower and higher, respectively, than in the other starches. ΔH followed the order: compound normal>waxy>normal≈zero amylose>high amylose>compound waxy. The SP followed the order: zero amylose>waxy>compound normal>normal>high amylose. A rapid increase in solubility occurred at lower temperatures (<70 °C) for zero amylose HB starch, however, this increase was gradual for the other starches. At 90 °C, solubility followed the order: high amylose>compound normal>normal>waxy. Zero amylose and waxy HB starches exhibited lower pasting temperatures, higher peak viscosities, and higher viscosity breakdown than normal HB starches. The extent of acid hydrolysis followed the order: zero amylose>compound waxy>waxy>normal>compound normal>high amylose. High correlations were observed between physicochemical properties and structural characteristics of HB starches.     

Effect of native crystalline structure of isolated potato starch on gelatinization behavior and consequently on glycemic response

Effect of crystalline structure of two isolated potato starches on gelatinization and glycemic response was studied. Both starches showed to possess different fine structures. Starch 1 exhibited a typical B-type X-ray diffraction pattern, while Starch 2 exhibited an X-ray diffraction pattern suggesting the presence of imperfections of the general B-type crystalline structure (peak at 5.5° 2θ was absent), hence disarraying the structure order. This difference was reflected in the gelatinization behavior and consequently in the glycemic response. Starch 2 started to melt at lower temperature than Starch 1 (e.g. T_o was 60.9 and 61.84 °C, respectively, to native starches), and residual gelatinization enthalpy (ΔH) of Starch 2 was always smaller than that of Starch 1 when heated at 54–65 °C for 10 min. Glycemic response was increased as gelatinization degree (DG) increased in starches independent from the native crystalline structure (area under curve = 2.59 × DG-75.83, R² = 0.986; maximum concentration of postprandial blood glucose = 0.042 × DG-0.23, R² = 0.935). Results suggested that native crystalline structure of isolated potato starch affects the glycemic response of heated starches by affecting the gelatinization behavior.     

Studies on the granular structure of resistant starches (type 4) from normal,high amylose and waxy corn starch citrates

Granular and crystalline structure of starch citrates from normal, high amylose and waxy corn starch were characterized using scanning electron microscopy (SEM), optical microscopy, X-ray diffraction and Fourier transform infrared spectroscopy (FT-IR) in this study. SEM showed that citric acid treatment induced changes in the morphology of starch granules. The granule structure of starch citrates was not collapsed or destroyed even after heating. Normal and high amylose corn starch citrates maintained birefringence but lost it upon heating at 100 °C for 30 min. However, waxy corn starch citrate showed no birefringence, even before heating. Starch citrates showed different X-ray diffraction patterns before and after heating. A new peak at 1724 cm⁻¹ (ester bond) was observed in FT-IR for all starch citrates before and after heating, indicating starch citrates were heat-stable. After the deconvolution of spectra, the intensity ratio of 1016 cm⁻¹/1045 cm⁻¹ was used to calculate the ratio of amorphous to crystalline phase in the starch citrates. The ratio of 1016 cm⁻¹/1045 cm⁻¹ increased with an increase in the degree of substitution.     

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.     

Enthalpy–entropy compensation in sorption phenomena of starch materials

The enthalpy–entropy compensation theory was applied to the experimental moisture adsorption and desorption isotherm data (water activity (a_w) range 0.006–0.982) of raw potato, potato starch gel, potato starch powder, highly amylopectin corn starch powder and highly amylose corn starch powder in the temperature range 30–60 °C. A linear relation existed between differential enthalpy (ΔH) and differential entropy (ΔS) for all the experimental data considered, thus satisfying the enthalpy–entropy compensation theory. Further analysis of the data indicated an enthalpy-controlled (isokinetic temperature (T_β) > harmonic mean temperature (T_hm)) and spontaneous (−ΔG) sorption process.     

Steady and oscillatory shear behaviour of semi-concentrated starch suspensions

The viscoelastic moduli G’ and G” of aqueous suspensions with 40% (w/v) normal corn starch (NCS) and waxy corn starch (WCS) were determined by oscillation rheometry. The oscillatory shear flow experiments at heating from 30° to 75 °C and maintaining at this temperature showed changes from a behaviour predominant viscous (G”>>G’) to predominant elastic (G’>G”) for both starches at 60.5 °C for WCS, respectively 70,85 °C for NCS, WCS having higher values of G’ and G” as NCS. After the gelatinisation temperature was attired, NCS showed no significant changes, both moduli remaining relatively constant. Peaks of both moduli G’ and G” were obtained for WCS at its maintaining at 75^oC, these changes being attributed to the changes in the amylopectin structure in the absence of amylose for this starch type. The frequency influenced the results; analysis at constant low frequency (10 s^-1) gave big oscillations during the measurements and made the analysis impossible, whereas frequencies as 50 s^-1 or 100 s^-1 gaves reproducible and similar results. The shear flow measurements realised at angular frequencies ω from10^-1 to 10³s^-1 at 25^oC showed that changes from a behaviour predominant elastic (G’>G”) to predominant viscous (G”>>G’) occurred when ω attired the values 10 s^-1 for WCS and 3 s^-1 for NCS. The calculation of the ‘Power-Law’ parameter B showed that NCS forms a physical gel structure, whereas WCS behaves as a covalent gel in the frequency domain 10^-1 to 10 s^-1 and as physical gel in the frequency domain 10 to 10² s^-1.     

Effect of cross-linking on the physicochemical and physiological properties of corn starch

Corn starch was chemically modified by cross-linking with STMP/STPP (99:1. w/w) and the physicochemical and physiological properties (in vitro and in vivo) of the cross-linked corn starch were investigated as a function of the degree of cross-linking. Cross-linking decreased the solubility, swelling factor, and paste clarity of corn starch. While the swelling factor was highly correlated with the degree of cross-linking (R² = 0.878), the X-ray diffraction patterns did not show any significant alteration in the crystallinity of corn starch. It was shown by SEM measurement that a black zone was observed on the surface of crossed-linked starch granules, which did not occur with native starch. When mice were fed the diets containing the corn starch with low (CLCS-5) and high (CLCS-12) degree of cross-linking (51.3 and 99.1%, respectively), significant effects on the final body weight, weight gain as well as perirenal weight of the mice (p < 0.05) were observed. Also, significant decreases in total lipid, triglyceride, and total cholesterol concentrations in serum were detected in CLCS-5 and CLCS-12 groups (p < 0.05). While total lipid level in the liver decreased with increasing degree of cross-linking, the triglyceride level was not affected by the supplementation with both of CLCS-5 and CLCS-12 corn starch samples.     

Thermal Behavior of Selected Starches in Presence of Other Food Ingredients Studied by Differential Scanning Calorimetery (DSC)–Review

ABSTRACT: This review article highlights the thermal behaviors of selected starches that were studied using differential scanning calorimetery (DSC) with data shown in various research publications. The starches of sago, potato, sweet potato, cassava, yam, and corn are included in this overview. Our examinations indicate that thermal properties are highly affected by the type of starch, its amylose/amylopectin content, and the presence of other food ingredients such as sugar, sodium chloride, water, milk, hydrocolloids, and meat. When the heating temperatures of the starches were increased, the DSC measurements also showed an increase in the temperatures of the gelatinization (onset [T_o], peak [T_p], and conclusion [T_c]). This may be attributed to the differences in the degree of crystallinity of the starch, which provides structural stability and makes the granule more resistant to gelatinization.     

Formation of starch spherulites: Role of amylose content and thermal events

Commercial maize starches and potato starches of two cultivars differing in physicochemical composition (granule size distribution; amylose to amylopectin ratio) and crystallinity were heated to 180 °C and then cooled by fast quench using a differential scanning calorimeter (DSC), in order to produce spherulitic starch morphologies. Among the raw maize starches, waxy maize starch had highest relative crystallinity (49%) whereas a lowest crystallinity of 33–39% was calculated for high-amylose maize starches. Potato starches showed a relative crystallinity of 50%. The temperatures and enthalpies of gelatinisation and melting varied among all the starches. High-amylose maize starches showed higher transition temperatures of gelatinisation (T_gel), whereas waxy maize starch had lowest T_gel and enthalpy of gelatinisation (ΔH_gel). Similarly, a considerable variation in parameters related with crystalline melting (T_m1, T_m2 and ΔH_m1, ΔH_m2) was observed for different starches. The superheated gels of different starches treated using DSC were subjected to polarised microscopy, to confirm the formation of spherulites. Both the high-amylose starch gels showed the presence of spherulites exhibiting birefringence and a weak crystalline pattern. No birefringence was observed for waxy maize starch gel, while potato starch gels had some birefringence. The particle size distribution of high-amylose maize starch gels analysed through Zetasizer showed the sizes of spherulitic particles fall in the range of 300 nm–900 nm. The scanning electron micrographs of the dried high-amylose maize starch gels showed the presence of round spherulites consisting of several aggregated spherulitic particles. Amylose content and melting of crystallites during heating play an important role during recrystallisation of amylose (spherulite morphologies).     

Digestibility and Pasting Properties of Rice Starch Heat‐Moisture Treated at the Melting Temperature (Tm )

Non‐waxy and waxy rice starches adjusted to 20% moisture (wet based, w.b.) were heated in a differential scanning calorimeter to determine the optimum parameters for producing slowly digestible starch (SDS). Starches heated to the temperature of melting (T_m) and held for 60 min in the calorimeter showed a slow digestibility compared to unheated samples. Digestibility decreased by 25 and 10%, respectively, for non‐waxy and waxy rice starches relative to non‐treated starches. Heat‐moisture treatment of waxy corn, non‐waxy corn and wheat starches at the T_m determined for non‐waxy rice starch did not result in significant decreases in digestibility. For waxy rice starches heat‐treated in microwave or conventional ovens at the T_m , there were slight but significant increases in digestibility of the treated starches compared to non‐treated starches at all incubation times. Digestibility was higher for starches heated for 30 min than for 60 min. Non‐waxy rice starches did not show any significant changes in digestibility. Heat‐moisture treatment at the T_m and the holding time of sample at that temperature in a differential scanning calorimeter were found to be significant to the formation of slowly digestible heat‐moisture treated starch.     

Relationships between texture,mechanical properties and structure of cornflakes

Hominies and flours derived from four corn varieties were prepared according to industrial recipes and processed as petals by extrusion cooking (SME = 150 J g⁻¹, T_die = 130 °C) and a batch thermal process (100 °C, 50 min). Flake texture was evaluated by crushing bulk petals in a Kramer cell and comparing measurements to those obtained for commercial cornflakes, previously graded by a trained sensory analysis panel. Depending on the corn variety, various results were found in regard to crispness. Bending moduli of dense extruded materials (E_s from 0.5 to 2.1 GPa) were found to be correlated to the texture of petals derived from the same blends. Results obtained at different scales showed that the expanded microstructure of flakes, determined by X-ray tomography, and the morphology of their constitutive materials, deduced from confocal scanning light microscopy and RVA, primarily depended on the process used rather than on the corn variety. Adhesion between protein aggregates and amorphous starch matrix was inferred from the mechanical properties involved in texture.     

Formation and stability of amylose ligand complexes formed by high pressure treatment

Starch can be gelatinized during high pressure processing in the presence of water, but to a greater or lesser extent. Starch gelatinization is often accompanied by the formation of amylose complexes, in particular when a thermal treatment is used. Four different starches were considered in this study: potato, broad bean (Vicia faba), pea and tapioca. A comparison between high pressure-induced starch gelatinization (HPG) and conventional thermal gelatinization (TG) was made. In the case of broad bean starch, selected complexing molecules were considered for both thermal and high pressure treatments. Cross polarization/magic angle spinning (CP/MAS) ¹³C NMR, X-ray diffraction and thermal analysis were used to monitor physico-chemical changes in the structure and microstructure of starch preparations. Decanoic acid and carvacrol were selected as complexing agents to track the formation of amylose ligand complexes. It was observed that B-type starch (potato) was more resistant to pressure than the A-type starches (tapioca, broad bean and pea) considered in this study. The results showed that amylose ligand complexes were formed during high pressure treatment (20 min at 500 MPa at temperatures of 20 °C and 40 °C). Decanoic acid induced the complexing of amylose in the V_6I type whatever the treatment used. On the other hand, the complexation of carvacrol appeared to depend on the temperature used during the high pressure treatment. It is assumed that carvacrol forms amorphous complexes with amylose during high pressure treatment. The amylose complexes were characterized by ¹³C CP/MAS NMR confirming the results obtained by X-ray analysis.Industrial relevanceDevelopment of innovative assembly of amylose + molecules of interest (i.e. antioxidant) using a mild processing (40 °C) instead of 90 °C. At 90 °C, some molecules are damaged or oxidized.The use of high pressure permits the production of larger amount of compounds than using conventional thermal treatment. The main reason is that there is no need to solubilise the molecule of interest.     

Structural and physicochemical properties and in vitro digestibility of recrystallized linear α-d-(1 → 4) glucans derived from mild-acid-modified cassava starch

Molecular structure and recrystallization method influence the techno-functional behaviour of recrystallized starch as a functional ingredient in foods. The physicochemical properties of debranched and recrystallized mild-acid-modified cassava starch were studied. Cassava starch was treated with 0.14 mol/L hydrochloric acid for 24, 96 and 216 h at 40 °C prior to debranching with pullulanase. The debranched starches (DS) were recrystallized by annealing (ANN-DS), temperature-cycling (TC-DS) or heat-moisture treatment (HMT-DS) and the particle distribution, crystallinity, thermal properties, solubility, water binding and in vitro digestibility were analyzed. Acid treatment increased the fraction of linear α-d-(1 → 4) glucans comprising 13–30 monomers. Particles comprised loosely to firmly coalesced primary elements forming aggregates of mono- or bi-modal size distribution at ?5 μm and ?20 μm. The relative crystallinities ranged between 31.1–56.1%. Water binding decreased significantly with acid treatment whereas both solubility and water binding were influenced by the recrystallization method and decreased in the order: DS > ANN-DS > TC-DS > HMT-DS. Major thermal transitions occurred at 80–130 °C and 130–160 °C, and the in vitro digestibility rates of 6.8–62.8% correlated significantly (p < 0.001) with relative crystallinity and melting enthalpy.     

Proximate Composition of Triangular Pea,White Pea,Spotted Colored Pea,and Small White Kidney Bean and Their Starch Properties

Physicochemical properties of beans and starches extracted from triangular pea, white pea, spotted colored pea, and small white kidney bean grown in China were investigated. Results pointed out that each of the different legumes might be a good resource of starch and protein, which could be utilized for specific applications in food processing. Starches separated from different legumes differed significantly with respect to their protein content, amylose/amylopectin ratio, lipid content, ash content, swelling power, and solubility. The scanning electron micrographs revealed the presence of kidney or elliptical- to irregular-shaped granules and with a diameter ranging from 5 to 40 μm. All starches exhibited a C-type X-ray diffraction pattern. The pasting properties were tested in a Rapid Visco Analyser and thermal properties with a differential scanning calorimeter. Small white kidney bean had the highest peak, trough, breakdown, and final viscosity among various starches. Triangular pea starch showed the highest gelatinization transition temperatures (T _o, T _p, and T _c) and enthalpy of gelatinization, while white pea starch showed the lowest transition temperatures and gelatinization enthalpy. The results obtained provide a technical basis for processing these legumes and starches.     

Comparison of the thermal characteristics of connective tissue in loose structured and normal structured porcine M. semimembranosus

The aim of the present study was to characterise the thermal properties of connective tissue in loose structured porcine SM muscles in comparison to normal looking SM muscles and to see whether the meat quality traits were related to the properties of connective tissue. Samples from the muscles with loose structure and light colour were selected by visual assessment and normal looking SM muscles were used as a control (n = 25 loose structured + 25 control). The loose structured muscles had lower ultimate pH (pH_u) than the control muscles. The onset and peak temperatures of thermal shrinkage of intramuscular connective tissue (T_o and T_p, respectively) in loose structured muscles were similar to those of control muscles when the full set of data (25 loose structured + 25 control) were analysed. When the T_o and T_p data from muscles the exhibiting ten lowest and ten highest pH_u values were analysed, the low pH_u muscles (all classified as loose structured) had lower T_o and T_p than the high pH_u muscles (all classified as control) (p < 0.05). Drip loss of loose structured SM muscles (11.1%) was dramatically higher than that of control muscles (3.9%). Collagen content and collagen solubility were similar in loose structured and control muscles. It seemed that changes in the properties of intramuscular connective tissue were more easier found in porcine SM muscles with low pH_u than in SM muscles with high pH_u.     

Physicochemical,Pasting, Thermal and Morphological Characteristics of Indian Water Chestnut (Trapa natans) Starch

Starch extracted from Indian water chestnut was investigated for its physicochemical characteristics. The results were compared with those obtained from two commercial starches (corn and potato). The pasting properties were tested in the Rapid Visco Analyser and thermal properties with a differential scanning calorimeter. Water chestnut starch possessed higher breakdown viscosity (BV) and setback viscosity (SV) than corn and potato starches. However, the pasting temperature of water chestnut starch was not significantly different from that of corn starch. Lower ΔH_gel values were obtained for water chestnut starch than for the other two starches whereas the onset, peak and conclusion temperatures of gelatinization (T_o, T_p and T_c) for water chestnut starch were quite comparable with corn starch. Scanning electron micrographs showed similarity in starch granule shape between water chestnut and potato starch with corn starch showing surface wrinkles on starch granule surfaces.