Retrogradation Enthalpy Research Articles

Staling of Cereal Bran Enriched Cakes and the Effect of an Endoxylanase Enzyme on the Physicochemical and Sensorial Characteristics

The staling of cakes enriched with untreated brans and endoxylanase-treated brans was evaluated by monitoring the changes in physicochemical, thermal, and sensorial properties of cakes during 7-d storage. Oat and rice bran were treated with different levels (0, 70, and 700 ppm) of an endoxylanase enzyme and added to cakes on 30% flour weight basis. Moisture losses, water activity, crumb firmness, starch retrogradation, and sensorial characteristics were used as staling indicators. Avrami-type equations were efficiently used for modeling the starch retrogradation kinetics, while linear models most adequately described crumb firming kinetics. Cake staling induced an increase in crumb firmness and enthalpy of amylopectin retrogradation, and a decrease in crumb moisture and sensory quality and acceptability scores of cakes. Oat bran-containing cakes better maintained their characteristics compared to the ones containing rice bran along the 7-d storage. Endoxylanase treatment of brans delayed the changes naturally induced during staling in crumb moisture content, amylopectin retrogradation enthalpy, and crumb firmness in the respective cakes. Deterioration of the sensorial characteristics was slower for the cakes containing endoxylanase-treated brans, as well. The level of endoxylanase treatment did not differentiate significantly (P < 0.05) any of the staling indicators. Overall, this study demonstrated that addition of endoxylanase-treated brans can result in cakes with improved nutritional characteristics and increased shelf life. The results of the study show the potential of using enzymes to modify underutilized food sources that can be properly incorporated in baked goods, improving their nutritional value, their quality characteristics, and providing longer shelf life. The developed procedure and results can be utilized by the bakery industry to make high fiber and low cost bakery products with improved sensorial characteristics that are appealing to the consumers.

Gelatinization, Pasting, and Gelling Properties of Sweetpotato and Wheat Starch Blends

ABSTRACTSweetpotato starch is high yielding but has very limited uses. It is possible to expand its application by blending it with other starches to obtain novel properties. In this study, functional properties of the blends of native sweetpotato starch with native, acid‐thinned, and hydroxypropylated wheat starch were studied at different ratios (75:25, 50:50, 25:75). The swelling factor, extent of amylose leaching, pasting, and gel textural properties of the blends were nonadditive of their individual components, and could be mathematically modeled by quadratic equations in relation to the ratios. Two peaks during pasting were observed for some starch mixtures studied by Rapid ViscoAnalyser (RVA). The gelatinization and retrogradation enthalpies (ΔH) of the blends were additive of their individual components and could be modeled by linear equations. All starch mixtures exhibited two peaks during differential scanning calorimetry (DSC) scan for gelatinization, but a single peak for retrograded starches. This study may provide basis for formulation of mixtures using starch from diverse sources to develop more natural starch systems with a range of physicochemical properties.

Physicochemical, Textural, and Nutritional Characterization of Mexican Rice Cultivars

ABSTRACTThe physicochemical properties, textural properties, and starch digestibility of rice cultivars grown in Mexico were evaluated. Variations existed in grain dimensions, and the rice grains were classified as medium, long, and extra long. Huimanguillo had the highest amylose content (30.4%), and A06, A92, A98, and Champoton presented the lowest amylose content (24.3–25.2%). The protein content was 7.1–11.0% and the lipid level was 0.47–1.22% among these Mexican cultivars. Champoton showed the highest temperature and enthalpy of gelatinization, and this with A98, Culiacan, and Huimanguillo had the highest enthalpy of retrogradation. Cotaxtla had the highest pasting peak, setback, and final viscosity. The texture assessment in cooked rice showed that A06 had the highest hardness, and A96 and A98 had the highest stickiness. There was little difference in the rapidly digestible starch, slowly digestible starch, and resistant starch content of tested Mexican rice cultivars. The differences in the physicochemical properties could be used to determine the end use of these Mexican rice cultivars.

Impacts of Low and Ultra-Low Temperature Freezing on Retrogradation Properties of Rice Amylopectin During Storage

Amylopectin retrogradation is a serious problem in starch-based ready meals. In the current research, rice amylopectin was frozen by low temperature (−20, −30, and −60°C) and ultra-low temperature (−100°C), and then stored at 4°C for 21 days or at −18°C for up to 5 months to evaluate the retrogradation properties. Amylopectin retrogradation enthalpy of rice was determined by a differential scanning calorimetry. The results showed that low temperature and ultra-low temperature freezing can effectively retard amylopectin retrogradation during the freezing process and during frozen storage (−18°C) for at least 5 months. However, rice amylopectin still retrograded after the freezing process during chill storage at 4°C. The methods of low and ultra-low temperature freezing combined with frozen storage might be potentially very useful for food industry to produce high quality starch-based ready to eat meals.

Differences of Physicochemical Properties for Waxy Maize Flour at Fresh and Maturity Stages

Understanding the differences of physicochemical properties of flours from different waxy maize cultivars at fresh and maturity stages could make its utilization proper.In the study,the flour physicochemical properties of five waxy maize cultivars at fresh and maturity stages were measured.The results indicated that the λmax was similar at two stages and presented typical waxy character.Heshengnuo 1512 harvested at maturity presented higher blue value(BV),whereas the other four cultivars had similar BV at two harvest stages.The flour presented higher starch content and lower protein content when the maize was harvested at maturity.The crystallinity and swell power at maturity were higher than those at fresh,whereas the solubility and light transmittance were lower at maturity,and the responses of the physicochemical characteristics to harvest stage were different for different cultivars.Zhongnuo 319 harvested at fresh presented higher viscosity characteristics and lower pasting temperature,whereas the viscosity properties for the other four cultivars were better at maturity,and Yuecainuo1 could not paste at fresh.Differential scanning calorimetry(DSC) results demonstrated that flour at maturity had lower transition temperature(onset,peak,and conclusion temperature),enthalpy of gelatinization(△Hgel),peak height index(PHI) and wider gelatinization range(R),whereas the percentage of retrogradation(%R) was lower at fresh.max was positively correlated to peak viscosity(r=0.63,P0.05),and negatively correlated to pasting temperature(r = -0.86,P0.01).Crystallinity was negatively correlated to pasting temperature(r = -0.70,P0.05),and positively correlated to △Hgel(r=0.74,P0.01),PHI(r=0.62,P0.05) and enthalpy of retrogradation(△Hret)(r=0.74, P0.01).%R was positively correlated to BV(r=0.64,P0.05),λmax(r=0.61,P0.05),crystallinity(r=0.69,P0.05),and △Hret (r=0.96,P0.01).Among the five cultivars,Zhongnuo 319 harvested at fresh presented higher starch content,crystallinity,and viscosity characteristics,which makes it better in fresh eating quality.Yuecainuo 1 at both harvest stages had the lowest %R among the cultivars,indicating its advantage using for the food that needs lower retrogradation.

Molecular structure, rheological and thermal characteristics of ozone-oxidized starch

The effects of oxidation by ozone gas on the molecular structure, rheological and thermal properties of starch (corn, sago and tapioca) were investigated. Starch, in dry powder form, was exposed to ozone for 10min at different ozone generation times (OGTs). Average molecular weight decreased in oxidized corn and sago starches but increased in oxidized tapioca starch. All oxidized starches exhibited non-Newtonian shear-thinning behaviour. Starch viscosity decreased drastically with increasing OGT. Young’s modulus for all oxidized corn and sago starch gels stored for 1 and 7days at 4°C increased significantly compared to unmodified starch. No differences were noted in gelatinization temperatures and gelatinization enthalpies of all oxidized starches compared to unmodified starch. Retrogradation enthalpy increased markedly in corn starch after 1min OGT. These results show that the extent of starch oxidation varies among starches of different botanical origins under similar ozone treatment conditions.

Thermal and rheological properties of granular waxy maize mutant starches after isoamylase modification

This work investigated the changes in the thermal and rheological property of two waxy maize mutant starches (Hsyn73 wxwx and Hsyn73 duwx) after they were treated with isoamylase in the granular state for various periods. The hydrolysis degrees reached in 168 h were 4.0% and 9.5% for the wxwx and the duwx, respectively. With increasing degree of hydrolysis, both wxwx and duwx generally showed an increase in gelatinization and retrogradation temperatures and retrogradation enthalpy. The weight average molar mass ( M w), z-averaged radius of gyration ( R z ), and pasting viscosity of both starches decreased when isoamylase hydrolysis progressed, however, the wxwx showed a greater decrease in M w and R z than the duwx at the same hydrolysis degree. Both wxwx and duwx, native or isoamylase-treated, displayed a similar pasting viscosity during holding and cooling when their amylopectin molecules had a similar R z . The study indicates the importance of R z in determining the pasting properties of waxy maize starch.

Effects of gamma-irradiation on the morphological, structural, thermal and rheological properties of potato starches

Changes in granule morphology, structural, thermal, gel textural and rheological properties of starches separated from two potato cultivars (Kufri Jyoti and Kufri Chipsona-2) caused by gamma-irradiation (Co 60, 0.01, 0.05, 0.1 and 0.5 kGy) were studied. A complete disorganization of the crystalline structure and carboxyl content of 0.09–0.11% was observed in starches irradiated at 0.5 kGy. Irradiation of starch increased gelatinization temperatures (onset-, peak- and conclusion-temperature) measured using DSC. Peak viscosity, trough viscosity, breakdown viscosity, final viscosity and gel hardness decreased while gel cohesiveness increased with the irradiation. Irradiation effect on gumminess, chewiness, adhesiveness and retrogradation of gels varied with the cultivar. Kufri Jyoti native and irradiated starches showed greater retrogradation as compared to Kufri Chipsona-2 native and irradiated starches. Difference in recrystallization of molecules as revealed from percent retrogradation and enthalpy of retrogradation amongst starch from two cultivars was also observed.

Effect of thermal processing and storage on digestibility of starch in whole wheat grains

Gelatinisation and retrogradation of starch in wheat flour systems and whole wheat grains were studied using DSC and the impact of these events on starch digestibility was investigated. Gelatinisation of starch was possible in wheat flours with more than 60% moisture content (dwb) and gelatinised samples had higher digestibility values. Retrogradation of starch was studied with partially and fully cooked (boiled at 100 °C for 12 min and 32 min, respectively) wheat grains that were subjected to storage at 22 °C for 48 h. Stored samples had lower digestibility values when compared to the freshly cooked counterparts. The effect of moisture on retrogradation was studied with fully cooked wheat grains that were dried to a range of moisture contents (14.6–35.9%, wwb) and stored at 20 °C for 24 h. Retrogradation enthalpy increased with increasing moisture content; however, digestibility values did not reflect the changes in retrogradation enthalpy. The possibility of estimating the degree of retrogradation in fully cooked grains (32 min cooking) was investigated using a wheat flour-water system. The retrogradation enthalpy of fully cooked grains was slightly higher than the wheat flour-water system (at a moisture content of 49%, wwb) during the course of storage at 22 °C.

Effect of succinylation on the physicochemical, rheological, thermal and retrogradation properties of red and white sorghum starches

Starches isolated from red and white sorghum were modified with succinylation. After modification proximate composition, moisture content, ash, protein and fat were reduced in percentage. Increase in swelling power was observed and did not show any significant change in solubility. Swelling and solubility were pH dependent with higher values obtained at pH 12 in both native and modified starches. At pH 4 both succinylated red and white starches had lower solubility. Rapid visco-analyser (RVA) revealed increased in peak viscosity of the succinylated starches and reduction in setback and breakdown values. There was no significant change in the pasting temperature. Gelatinization enthalpy reduced from 1.275 and 1.953 J/g in RNS (red native starch) and WNS (white native starch) respectively to 1.105 and 1.178 J/g in SUCR (succinylated red starch) and SUCW (succinylated white). Endothermic transition temperatures (T o, T p and T c) reduced and the retrogradation enthalpy increases with the storage time of gelatinized starches. Therefore retrogradation tendency was reduced by succinylation.

Hydroxypropylation of pigeon pea (Cajanus cajan) starch: Preparation, functional characterizations and enzymatic digestibility

Hydroxypropyl starch derivatives were prepared from pigeon pea starch (NPPS) which is an unconventional starch source. Functional parameters and characterization of both native and modified starches were carried out. The starch granules appeared oval or elliptical in shape with sizes ranging from 7 to 40 μm in width and 10 − 30 μm in length. Hydroxypropylation did not alter the shape of the starch granules in a pronounced way. Generally, the x-ray diffractograms of native pigeon pea starch showed the “A” pattern. However, slight reductions in the diffraction intensity of starches after modification were observed. At all temperatures studied (30–90 °C), swelling and solubility of hydroxypropylated starches were higher than the NPPS. Progressive increases in swelling capacity and solubility were observed as the molar substitution (MS) increased among the hydroxypropylated starches. Hydroxypropylation reduced starch paste turbidity on storage. Also, studies showed that syneresis reduced after hydroxypropylation. In addition, syneresis reduced as the MS of the hydroxypropyl starches increased. The results indicate that pasting temperature and peak temperature reduced after modification but peak viscosity increased in hydroxypropylated starch derivatives compared with the native starch. Setback reduced in hydroxypropylated starches compared with the native starch. Enthalpy of gelatinization and percentage retrogradation reduced after hydroxypropylation and progressive reductions were observed as the MS increased among the starch derivatives. Hydroxypropylation increased enzymatic digestibility.

Preparation of starches with low glycaemic response using amylosucrase and their physicochemical properties

Enzymatic modification by amylosucrase (AS) from Neisseria polysaccharea was used on waxy rice, normal rice, waxy corn, normal corn, waxy potato, and normal potato starches to prepare the starches with a high content of slowly digestible starch (SDS) fraction. The AS-treated starches contained similar amounts of resistant starch, decreased rapidly digestible starch, and increased SDS compared to controls. After the AS treatment, the SDS contents increased by approximately 25% in waxy starches but about 8% in normal starches. The yields of the insoluble fraction of waxy starches were about 15% higher than those of normal starches. The branch chain length was increased by DP 13–19. The AS-treated starches showed a B-type X-ray diffraction pattern, 5–9 J/g for retrogradation enthalpy, 88–89 °C for peak temperature, and much larger moduli for their gels compared with raw starches.

Effects of freezing rates on starch retrogradation and textural properties of cooked rice during storage

The effects of freezing rates and storage temperatures on starch retrogradation and textural properties of cooked rice were evaluated. Cooked rice was frozen with different freezing rates and then stored at 4 °C for 14 days or −18 °C for up to 7 months. Starch retrogradation enthalpy (Δ H r) of cooked rice was determined by a differential scanning calorimetry, and textural properties were determined by a texture analyser. The results showed that the Δ H r and hardness values had a negative correlation with freezing rate, however, a positive correlation was found between adhesiveness and freezing rate. On the other hand, the advantages (lower hardness and higher adhesiveness, less starch retrogradaton) of cooked rice gained by rapid freezing, were lost quickly in the first 3 days of storage at 4 °C. However, rapid freezing combined with −18 °C frozen storage can effectively retard starch retrogradation and maintain the textural properties of cooked rice for at least 7 months. Therefore, high quality cooked rice can be produced by combined rapid freezing with frozen storage.

Isolation of starch from two wheat varieties and their modification with epichlorohydrin

The aim of this research was determination of influence of wheat variety and modification with epichlorohydrin on starch properties. Starch was isolated from two wheat varieties: “Golubica” and “Srpanjka” and modified with different concentrations of epichlorohydrin (0.1%, 0.3% and 0.5% v/w). Both native and modified starches were characterised. Results showed similar characteristics of native wheat starches. Modification with epichlorohydrin increased temperature of gelatinisation, but gelatinisation and retrogradation enthalpy were affected by the extent of the chemical reaction between starch and epichlorohydrin, due to differences in reactivity between wheat starch varieties. Maximum viscosity decreased as well as breakdown and setback values. Swelling power and solubility were also decreased by modification, while paste clarity and freeze–thaw stability were influenced differently, due to different extent of the chemical reaction between different starch varieties and epichlorohydrin. Colour of starch was not significantly altered by modification. Digestibility of starches can be reduced by proper selection of epichlorohydrin concentration used for modification.

The effects of xanthan and guar gums on staling of gluten‐free rice cakes baked in different ovens

SummaryThe objective of this study was to determine the effects of different concentrations of xanthan and guar gums and their blends on staling of gluten‐free rice cakes baked in microwave‐infrared combination oven (MW–IR) and to compare the cakes with conventionally baked ones. Gums were added at concentrations of 0.3% and 1.0%. For preparation of gum blend, 0.5% xanthan gum was mixed with 0.5% guar gum. In order to understand the staling behaviour of cakes, cakes were stored at 22 ± 2 °C for 120 h. Xanthan‐guar gum blend decreased hardness, weight loss, retrogradation enthalpy and the change in setback viscosity values of cakes during storage for both types of ovens as compared to control formulation. It was found that oven type was a significant factor in affecting staling parameters of gluten‐free cakes.

A study of the retrogradation process in five argentine rice starches

Rate of the retrogradation process of five new argentine genotypes rice starches with different amylose contents and gelatinization temperatures during storage at 4.5 ± 0.5 °C was studied using differential scanning calorimetry (DSC). Significant differences were not found among transition temperatures, i.e., T 0 (onset temperature), T p (peak temperature) and T c (conclusion temperature), of non-waxy genotypes when studied using DSC. An increased retrogradation enthalpy (Δ H, mJ/mg) with the storage time occurred with all non-waxy samples. The waxy genotype, W4109, did not show a retrogradation peak for the period under study. Genotypes with high total amylose content (TAM) retrograded more than those with lower content. The kinetic parameters “ k” and “ n” were evaluated using the Avrami model appearing to be related to the water-soluble amylose (SAM) content. Relationship between the retrogradation degree (% R) and the water-insoluble amylose (IAM) content was found. Gelatinization temperature of the starch ( T G) seemed to affect the retrogradation rate.

In vitro digestibility, structural and functional properties of starch from pigeon pea (Cajanus cajan) cultivars grown in India

Abstract Starches isolated from two pigeon pea cultivars (AL-15 and AL-201) were evaluated for their in vitro digestibility, structural and functional properties. Both the cultivars exhibited a characteristic C-type diffraction pattern with relative crystallinity values of 31.9% and 34.2%, for AL-15 and AL-201, respectively. The structural characterization obtained using high performance size exclusion column chromatography revealed that molecular weight of amylopectin and amylose was higher for AL-201 (396 and 3.92 × 106 g/mol, respectively) in comparison to AL-15 starch (354 and 3.31 × 106 g/mol, respectively). AL-201 exhibited higher values for transition temperatures, enthalpy of gelatinization, pasting temperature and percentage retrogradation in comparison to AL-15 starch. Slowly digestible starch, readily digestible starch and resistant starch contents of AL-15 and AL-201 cultivars were observed to be 31.0, 8.1 and 60.9% and 29.6, 5.2 and 65.2%, respectively. The hydrolysis index and RS values indicated that pigeon pea starches were highly resistant to digestion.

Retrogradation properties of high amylose rice flour and rice starch by physical modification

A new physical modification applied to prevent the retrogradation of rice flour and rice starch was investigated. This study examined the retrogradation properties of treated rice flour or rice starch paste by three stirring or heating–stirring, or without. The results proved that the retrogradations of rice flour and rice starch were both not substantially affected by three stirring modifications. However, three heating–stirring treatments had a marked effect on retarding the retrogradation of rice flour, but did not affect that of isolated rice starch. In the differential scanning calorimetry (DSC) analysis, modified rice flour by three heating–stirring exhibited the lowest retrogradation enthalpy (3.04 J/g dry matter) as compared to the control RF (5.93 J/g dry matter) and by three stirring (5.08 J/g dry matter). Meantime, it had almost the least recrystallization of retrogradation by X-ray diffraction (XRD). It was also found through scanning electron microscopy (SEM) that the granule structure of this modified rice flour had a more honeycomb-like structure and the lowest crystallinity as compared to the others.

Impact of cooling rates on the staling behavior of cooked rice during storage

The impact of cooling rates (0.40, 1.11, 1.42, 1.64, 2.47 and 3.36 °C/min) on starch retrogradation and textural properties of cooked rice was evaluated. The relationship between cooling rates and different properties were determined using Pearson correlation. Starch retrogradation enthalpy (Δ H r) of cooked rice was determined by differential scanning calorimetry, and textural properties were determined by a Texture Analyser. This study showed that the Δ H r value and hardness value had a negative correlation with cooling rate during storage, −0.963 ⩽ r ⩽ −0.716, P < 0.01; −0.826 ⩽ r ⩽ −0.706, P < 0.05, respectively. However, a positive correlation was found between adhesiveness and cooling rate (0.237 ⩽ r ⩽ 0.882, P < 0.05). These results indicated that the cooked rice chilled with slower cooling rate retrograded faster than chilled with rapid cooling rate. Therefore, high quality cooked rice can be produced by rapid cooling process.

Starch Gelatinization and Retrogradation Properties under Different Basic Fertilizer Regimes and Nitrogen Topdressing at Jointing Stage of Waxy Maize

Proper fertilizer managements can improve the starch gelatinization and retrogradation properties of waxy maize(Zea mays L.Ceratina Kulesh).The split-design experiment was conducted using waxy maize cultivar Suyunuo 4 with four main plots subjected to basal fertilizer treatments of N 75 kg ha-1,N 75 kg ha-1+K2O 70 kg ha-1,N 75 kg ha-1+P2O5 65 kg ha-1,and N 75 kg ha-1+P2O5 65 kg ha-1+K2O 70 kg ha-1,respectively in 2007 and 2008.The three split plots were topdressed with nitrogen of 0,150,and 300 kg ha-1 at jointing stage,respectively.Though onset temperature(To),peak temperature(Tp) and conclusion temperature(Tc) of native starch and retrogradated starch were affected by fertilizer treatments,the variation was little.No significant effects were observed for basic fertilizer treatments on the enthalpy of gelatinization(ΔHgel),and for N topdressing treatments on gelatinization range(R) and peak height index(PHI).The R-value was the lowest in the treatment with only N and K in basal fertilizer,and the highest in the treatment with N,P,and K in basal fertilizer.The changes of PHI showed an opposite trend to R.The ΔHgel was the highest in the treatment with medium N topdressing(150 kg ha-1).Gelatinized starch became retrograded with lower To,Tp,Tc,enthalpy of retrogradation(ΔHret),and PHI,as well as wider R.Compared with the treatment of only N applied in basal fertilizer,the percentage of retrogradation and ΔHret decreased when P and/or K added in the basal fertilizer.The two indicators were higher in the treatments with N topdressing than without N topdressing.The percentage of retrogradation was posi-tively correlated with ΔHret(r = 0.90,P 0.01) and PHI of retrograded starch(r = 0.41,P 0.05).ΔHgel was positively correlated with PHI(r = 0.65,P 0.01) and ΔHret(r = 0.44,P 0.05),but negatively correlated with Tc(r =-0.41,P 0.05).It is recommended to apply balanced fertilization with N,P,and K combining with moderate N topdressing under conditions similar to the experiment to improve gelatinization and retrogradation properties of waxy maize starch.