Dry Heating Treatment Research Articles

Effect of dry heating treatment on multi-levels of structure and physicochemical properties of maize starch: A thermodynamic study

Dry heating treatment (DHT) is a common process widely used in food industry. In this study, the thermodynamic effects of DHT on starch structure and physicochemical properties are investigated. The results show that, with heating temperature increasing during DHT, the molecular size, long-amylose chains with degree of polymerization (DP) ~5000–20,000, and the crystallinity of maize starch are significantly reduced while the granular structure is retained with slightly aggregation between starch particles. The solubility of DHT starch increases from 0.5% to 2%, indicating the majority of DHT starch is still insoluble. DHT affects starch thermal property greatly that, it decreases the gelatinization enthalpy while increases the heterogeneity of starch crystallites. With heating temperature increasing, DHT reduces the overall viscosity of starch paste. The rheological property of DHT starch is frequency-dependent, showing the typical shear thinning behavior and “solid-like” gel property. Especially, as heating temperature reaches 190 °C, the shear resistance becomes stronger, and it is closer to Newtonian fluid. The results prove the thermodynamic effects of DHT on multi-levels of starch structure and physicochemical properties, also indicating the great potential to utilize DHT in modifying starch properties and amplifying its applications.

Optimisation of the Preparation of Sweet Potato Resistant Starch by Dry Heating with Pectin

The technological conditions for preparing sweet potato resistant starch (RS) by utilising the synergy of dry heating with pectin were optimised. By applying a response surface method, the influences of concentration of pectin, dry-heating treatment time, and dry-heating treatment temperature on starch anti-digestibility of sweet potato starches were analysed. The results showed that the optimal technological conditions were as follows: the content of pectin, dry-heating time, and dry-heating temperature were 2.18%, 2.09 h, and 121.73 °C, respectively. The RS content in sweet potato starches prepared under these conditions was within 18.48% ± 0.73%. The result obtained through differenti0al scanning calorimetry (DSC) revealed that the heat enthalpy (ΔH) of sweet potato starch increased from 2.475 to 3.698 J/g after being subjected to dry heating with pectin. Moreover, the result of in vitro digestibility tests suggested that the glycemic index of sweet potato RS prepared through dry heating with pectin was 69.09.

Preparation of cassava starch hydrogels for application in 3D printing using dry heating treatment (DHT): A prospective study on the effects of DHT and gelatinization conditions.

3D printing is a technology capable of presenting creative, unique and intricate items in an attractive format, with specific compositions. However, novel ingredients must be developed to satisfy this new technological requirement. This work proposes dry heating treatment (DHT), a simple physical technique, as a method for modifying cassava starch, with particular focus on its use for 3D printing. DHT processing was conducted at 130°C for 2 and 4h (named DHT_2h and DHT_4h, respectively). Different gelatinization conditions (65, 75, 85, and 95°C) were applied, and the hydrogels were evaluated considering different storage periods (1 and 7days). Cassava starch properties were evaluated, focusing on the application of its hydrogels to 3D printing. The increase of DHT time produced a starch with higher carbonyl content and bigger granule size. It also reduced the water absorption index, increased the water solubility index, affected granule crystallinity and reduced molecular size. The longest storage period increased gel firmness. Increasing the temperature used in the gelatinization process reduced the gel strength of the native and DHT_2h. DHT_4h showed the lowest peak apparent viscosity and provided the strongest gels for all the evaluated conditions. Gels produced with DHT starches exhibited better printability than the native starch, mainly for the DHT_4h. This treatment was chosen to print 3D stars, and displayed better resolution than the native gels. Therefore, by using DHT, it was possible to obtain hydrogels with enhanced pasting properties, gel texture, and printability, thereby expanding the potential of applying cassava starch to 3D printing.

The impacts of particle size on starch structural characteristics and oil-binding ability of rice flour subjected to dry heating treatment

As a main starch source in human diet, milled rice flour has been widely used in various foods, and its particle size may impact the quality of final products. This study investigated the effects of particle size on starch structure and oil-binding ability of rice flour subjected to dry heating treatment. The results showed that fine fraction of rice flour had lower starch content. All samples showed A-type crystalline structure of starch, and this crystalline type was not changed by dry heating treatment, although the crystallinity was reduced. Rice flour with smaller size exhibited lower starch gelatinization temperatures and enthalpy change, and displayed higher hydrophobicity and oil-binding ability. The hydrophobicity of rice flour was improved by dry heating as observed from the increased three-phase contact angle, attributing to elevated surface hydrophobicity of rice protein. These results will provide guidance for developing functional ingredients with improved oil-binding ability for non-gluten foods.

Dry heating and annealing treatment synergistically modulate starch structure and digestibility

To modulate starch digestibility, dry heating combined with annealing treatment was employed to synergistically modulate structure and digestibility of normal maize starch (NMS) and potato starch (PS). Dry heating decreased starch molecular weight and created small molecular fractions with suitable chain length, resulting in starch better rearrangement during annealing treatment. Accordingly, after dry heating combined with annealing treatment starches had the highest pasting temperature, the thinnest and the thickest of crystalline lamellae for NMS and PS, respectively, and the highest ordered structures of cooked-starch compared with single dry heating or annealing modified starches. The results revealed that the synergistic modification altered starch lamellar thickness and increased double helices orders. Thereby, dry heating combined with annealing treated starches exhibited the lowest enzymatic digestibility with increased ca. 7.90% of slowly digestible starch for NMS or elevated ca. 5.04% of resistant starch for PS. The differential changes caused by dry heating combined with annealing treatment between NMS and PS were comprehensively discussed and the difference should result from the different starch crystalline structure and average chain length. This study provides a promising pathway for modulating starch structures and enzymatic digestibility.

Impact of continuous and repeated dry heating treatments on the physicochemical and structural properties of waxy corn starch

In order to investigate the impact of continuous dry heating treatment (CDHT) and repeated dry heating treatment (RDHT) on the structural and physicochemical properties of the waxy corn starch, the starch was prepared at 140 °C for continuous 20 h or for 5 cycles of heating, respectively. Each cycle lasted 4 h and the interval between each cycle was 1 h of cooling at room temperature. It turned out that RDHT and CDHT caused the aggregation of the starch into big lumps. The crystal type of CDHT and RDHT starches remained A-type, while the relative crystallinity and the short-range molecular order of starch characterized with 1040 cm−1/1018 cm−1 increased during first 2 circulations of RDHT and first 8 h of CDHT afterwards decreased upon the increased duration. After the heat treatment the water absorption index, swelling volume, viscosity and thermal parameters of CDHT and RDHT starches decreased, but the solubility, paste clarity and paste temperature of starches increased compared with native starch. Taken together RDHT has a greater impact on decreasing transmittance of starch paste, weakening the resistance to shear force and increasing retrogradation degree of starch paste compared to CDHT for the same duration.

Controlled fragmentation of starch into nanoparticles using a dry heating treatment under mildly acidic conditions

Normal corn starch was treated with acidic ethanol solution with various concentrations of ethanol (0, 10, 30, 50 and 95%) and acid (0.0026, 0.0053 and 0.0079M) and then subjected to a dry heating treatment for 1, 2 and 4h at 130°C to prepare starch nanoparticles. Size of nanoparticles was determined using DLS (dynamic light scattering). FT-IR (Fourier-transform infrared spectroscopy), XRD (X-ray diffraction) and TEM (transmission electron microscopy) were used to determine the structure and morphology of starch nanoparticles. As the ethanol concentration decreased, the starch granule readily fragmented into smaller particles when simply dispersed in water, and this was possibly by the preferential hydrolysis of the starch chains in the amorphous region. A higher ethanol concentration (50 and 95%) did not produce homogenous nanoparticles, however 30% ethanol concentration produced uniform nanoparticles with a mean diameter of 46.4nm. The treatment condition (30% ethanol) partially broke the long-range crystalline order but left the short range order of the spherical nanoparticles intact. However, lower ethanol (<30%) concentrations induced severe damages in the both crystalline structures (long and short range) of starch granule.

Effect of different stabilisation treatments on preparation and functional properties of rice bran proteins

The stabilisation treatments of rice bran were performed using microwave heating (100% power, 1–2 min) and dry heating (120°C, 10–20 min), respectively, and then protein was prepared by alkaline extraction (pH 9.5) and acid precipitation (pH 4.5). Stabilisation treatments resulted in a decrease in the protein yield, but an increase in the pro­tein purity. Heat-stabilisation was effective in inhibiting the rancidity of rice bran, and microwave heating was more effective than dry heating. The functional properties of proteins such as the emulsifying properties and oil holding capacity were improved with the stabilised rice bran, while the foaming properties, water holding capacity and nitrogen solubility of protein were slightly impaired. By comparison, dry heating treatment at 120°C for 20 min was effective and suitable for the stabilisation of rice bran for long term storage, as well as improving some functional properties of rice bran proteins. These results could provide basic information for industrial preparation of rice bran protein and its application in various food formulas.

Super-Cationic Carbon Quantum Dots Synthesized from Spermidine as an Eye Drop Formulation for Topical Treatment of Bacterial Keratitis.

We have developed a one-step method to synthesize carbon quantum dots (CQDPAs) from biogenic polyamines (PAs) as an antibacterial agent for topical treatment of bacterial keratitis (BK). CQDs synthesized by direct pyrolysis of spermidine (Spd) powder through a simple dry heating treatment exhibit a solubility and yield much higher than those from putrescine and spermine. We demonstrate that CQDs obtained from Spds (CQDSpds) possess effective antibacterial activities against non-multidrug-resistant Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella enterica serovar Enteritidis bacteria and also against the multidrug-resistant bacteria, methicillin-resistant S. aureus. The minimal inhibitory concentration (MIC) of CQDSpds is ∼2500-fold lower than that of spermidine alone, demonstrating their strong antibacterial capabilities. Investigation of the possible mechanisms behind the antibacterial activities of the as-synthesized CQDSpds indicates that the super-cationic CQDSpds with small size (diameter ca. 6 nm) and highly positive charge (ζ-potential ca. +45 mV) cause severe disruption of the bacterial membrane. In vitro cytotoxicity, hemolysis, hemagglutination, genotoxicity, and oxidative stress and in vivo morphologic and physiologic cornea change evaluations show the good biocompatibility of CQDSpds. Furthermore, topical ocular administration of CQDSpds can induce the opening of the tight junction of corneal epithelial cells, thereby leading to great antibacterial treatment of S. aureus-induced BK in rabbits. Our results suggest that CQDSpds are a promising antibacterial candidate for clinical applications in treating eye-related bacterial infections and even persistent bacteria-induced infections.

Identification and quantification of the phosphorylated ovalbumin by high resolution mass spectrometry under dry-heating treatment

The specific phosphorylation sites and degree of phosphorylation (DP) at each site are directly related to protein’s structure and functional properties. Thus, characterizing the introduced phosphate groups is of great importance. This study was to monitor the phosphorylation sites, DP and the number of phosphorylation sites in P-Oval achieved by dry heating in the presence of pyrophosphate for 1, 2 and 5days by using Fourier transform ion cyclotron mass spectrometry (FTICR MS). Two phosphorylation sites were found in natural ovalbumin, but the number of phosphorylation sites increased to 8, 8 and 10 after dry-heating phosphorylation for 1, 2 and 5days, respectively. In addition, dual-phosphorylated peptides were detected for samples without extensive heating. The phosphorylation sites were found to be mainly on Ser residues, which could be the preferred phosphorylation site for dry heating in the presence of pyrophosphate.

A validated stability-indicating TLC-densitometric method for the determination of stanozolol in pharmaceutical formulations

BackgroundStanozolol is a synthetic derivative of dihydrotestosterone (DHT), and one of the frequently detected anabolic steroids in doping analysis. The current work describes the development and validation of the stability-indicating TLC-densitometric method for sensitive and specific estimation of stanozolol even its degradation product being there. Precoated silica gel TLC aluminium plates were utilized as the stationary phase and the eluent comprised of petroleum ether: acetone (6:4, v/v). Densitometric analysis of stanozolol was achieved at λmax 750 nm in the absorbance mode after staining with phosphomolybdic acid (PMA). Stress degradation of stanozolol was carried out under various reaction conditions including acid, base and neutral hydrolysis, wet and dry heating treatment, oxidation, and photo-degradation. Resulted stress samples and pharmaceutical products were analyzed with the developed TLC method.ResultsThis system showed a compact spot for stanozolol at Rf value of 0.46 ± 0.02. The data of linear regression analysis indicated a good linear relationship over the range of 200–1200 ng/spot concentrations. The method was validated for robustness, precision and recovery. The LOD and LOQ were 1.6 and 5.1 ng/spot, respectively. Under various stressed conditions, stanozolol showed degradation only under acidic hydrolysis. Peak of a degraded product was well resolved from the stanazolol with reasonably different Rf value and identified as 17, 17-dimethyl-l8-nor-5α-androst-13(14)-eno [3,2c] pyrazole through 1D- and 2D-NMR spectroscopic techniques and ESI-QqTOF-MS/MS analysis.ConclusionResult reflected that the stanozolol is majorly affected by the acidic condition. Statistical analysis indicated the application of the developed stability-indicating TLC-densitometric method for routine analysis of stanozolol in the presence of its degradation product.

Structural consequences of dry heating on alpha-lactalbumin and beta-lactoglobulin at pH 6.5

In the present work, we investigated the structural modifications occurring during the dry heating of model whey proteins, β-lactoglobulin and α-lactalbumin. Samples were adjusted to pH 6.5, water activity aw=0.23 and dry heated at 100°C for up to 24h, and the structural modifications followed by gel permeation chromatography, reverse phase-HPLC, SDS PAGE and mass spectrometry (LC–MS/MS). The dry heating treatment traps a fraction of the proteins into covalently linked soluble aggregates. Moreover, a high proportion of non-aggregated α-lactalbumin (about 73%) was converted into non-native forms. The characteristic of those non-native species was the loss of one or two water molecules per α-lactalbumin molecules. Using tandem mass spectrometric peptide mapping, these chemical modifications were found to be attributed to (i) the formation of a pyroglutamic acid from the N-terminal glutamic acid and (ii) the formation of an internal cyclic imide at position Asp64. The non-native species were not favored in the case of β-lactoglobulin as they represented less than 18% of non-aggregated proteins.

Stress degradation studies and stability-indicating TLC-densitometric method of glycyrrhetic acid

BackgroundGlycyrrhetic acid, a pentacyclic triterpenoid, possesses a broad range of pharmacological activities and serves as template to synthesize many bioactive drugs. This paper describes a simple, accurate, and sensitive stability-indicating TLC densitometric method for the determination of glycyrrhetic acid and its degradation product as per the ICH guidelines.ResultsSeparation was carried out on TLC aluminium sheet pre-coated with silica gel 60F254 using chloroform, methanol and formic acid (9:0.9:0.1, v/v). Compact spot for glycyrrhetic acid was found at Rf value of 0.42 ± 0.03. Densitometric analysis was carried out in the absorbance mode at λmax 254 nm. Glycyrrhetic acid was found to be stable to the exposure of base, neutral, oxidation, dry heating treatment and wet heating treatment, but showed degradation under acidic and photochemical conditions. Moreover, fragmentation pattern of glycyrrhetic acid was developed by using a positive ion electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QqTOF-MS/MS) hybrid instrument. A photo-degraded product was characterized through comparison of mass spectrometric studies with glycyrrhetic acid.ConclusionThe developed stability-indicating TLC-densitometric method can be applied for routine analysis of glycyrrhetic acid in the presence of its degradation products.

Study on the rheological properties of heat-induced whey protein isolate–dextran conjugate gel

Effect of glycosylation on the rheological properties of whey protein isolate (WPI) during the heat-induced gelation process was evaluated. Significant changes in browning intensity, free amino groups content and SDS-PAGE profile showed that the conjugate of WPI and dextran (150 kDa) was successfully prepared using the traditional dry-heating treatment. For the conjugate, during the heating and cooling cycle, the curves of G′ and G″ were considerably shifted to lower values and their shapes varied comparing to the corresponding spectra of initial WPI and WPI + dextran mixture. After holding at 25 °C, G' reached a value of about 2200 Pa, only a tenth of the value that obtained in the initial WPI gel. Moreover, frequency sweep measurements revealed that the stiffness of gel was greatly reduced in the conjugate, although a typical elastic gel was still formed. All data showed that the rheological properties of thermal gelation could be modified upon the covalent attachment of dextran.

Response of common carp fry fed diets containing a pea seed meal ( Pisum sativum) subjected to different thermal processing methods

Three forms of pea seed meal (native - NAT Diet, autoclaved - AC Diet and dry cooked - DC Diet) were evaluated in balanced diets for common carp fry ( Cyprinus carpio L.) replacing solvent extracted soybean meal protein in a fish meal / soybean meal based control diet (CTR Diet). After a 49- day growth trial, weight gain, feed conversion ratio, protein efficiency ratio and apparent net nitrogen utilization of fish fed the fish meal / soybean meal diet (CTR Diet) and of that fed the pea seed meal subjected to different thermal treatments were determined. Significant differences ( P < 0.05 ) were found in the mean final weight (MFW) and specific growth rates (SGR) between fish fed the CTR and NAT Diets (i.e., mean final weight: 30.69 and 25.70 g, respectively; SGR: 2.84 and 2.51 g, respectively). The mean final weight of carp fed the autoclaved pea seed meal diet (MFW 28.40 g, AC Diet) and the group fed the dry cooked pea seed meal diet (MFW 29.34 g, DC Diet) were not deemed significantly ( P > 0.05 ) different to those of carp fed the fish meal / soybean meal control diet. A sequential digestibility study was also undertaken to complement the growth trial. Apparent nutrient and energy digestibility coefficients (ADCs) reflected a similar trend as results in the first trial. Apparent nutrient and energy digestibility coefficients were found to be highest when fish were fed the CTR Diet. Apparent digestibility coefficients of carp fed the AC and DC Diets were generally higher than that of the NAT Diet. Overall, ADC's of fish fed the DC Diet were generally higher than that of the AC Diet. It can be concluded that thermal treatment can nutritionally modify pea seed meal to some extent: the dry heating treatment proved to be slightly more effective than the moist heat treatment in terms of growth performance, feed utilization efficiency and apparent digestibility in common carp.

Whey protein–maltodextrin conjugates as emulsifying agents: An alternative to gum arabic

The emulsifying properties of covalent complexes of maltodextrin (MD) with whey protein (WP) isolate have been investigated under both acidic and high electrolyte concentration conditions in systems containing medium-chain triglyceride oil or orange oil. Covalent coupling of protein to polysaccharide was achieved by dry-heat treatment of a protein+polysaccharide mixture for up to 2 h. It was confirmed by SDS-polyacrylamide gel electrophoresis that the WP does become directly linked to the MD. Analysis of droplet-size distributions has shown that this covalent linking of MD to WP leads to a very substantial enhancement in the protein emulsifying behaviour under both acidic and neutral conditions. Analogous dry-heating treatment of MD with soy protein does not have this positive effect. A whey protein–MD conjugate WP–MD19, made from MD (DE=19) of intermediate mean molecular weight (8.7 kDa), has been found to be capable of producing fine emulsion droplets (0.5–1 μm) with either triglyceride oil or orange oil. Optimized WP–MD19 conjugates can produce fine stable emulsions (20 vol% oil) at 2 wt% emulsifier content, whereas the equivalent emulsion made with gum arabic requires a 20–30 wt% level of emulsifier. A WP–MD19 conjugate of protein/polysaccharide ratio 1:2 or 1:3 is effective in stabilizing low-pH emulsions of a commercial flavour oil (containing a weighting agent) over a storage period of several weeks, with no visible precipitation or phase separation when mixed with colouring agents, either before or after extensive emulsion dilution.

Selective Isolation and Distribution of Actinomadura rugatobispora Strains in Soil.

A simplified enrichment method for selective isolation of Actinomadura rugatobispora strains from soil is described. A. rugatobispora strains poorly produced spores on agar media when 5 to 20 colonies grew on a plate while characteristic spore formation was observed on humic acid-MOPS gellan gum medium. Spores of A. rugatobispora strains were tolerant to dry heating treatment at 120°C for 60 min. A. rugatobispora strains were resistant to 50 μg/ml trimethoprim and 10 μg/ml nalidixic acid, both of which inhibited the growth of nonfilamentous soil bacteria. In addition, these strains were more resistant to 100 μg/ml gentamicin and 20 μg/ml ampicillin than Streptomyces strains, which interfere with the growth of A. rugatobispora selectively. Owing these characteristics, we were successful to isolate 260 strains of this species from 148 out of 547 soil samples (27% of the samples tested). They were recovered from the soil samples with pH values ranging from 5.0 to 8.6, and 91% of the strains were isolated from neutral to slightly alkaline soil (pH 6.0 to 9.0). These results indicated that A. rugatobispora strains were distributed worldwide.

Emulsion stabilization by ionic and covalent complexes of β-lactoglobulin with polysaccharides

The influence of protein—polysaccharide interactions on the surface and emulsifying properties of β-lactoglobulin at pH 7 has been investigated for systems containing the non-ionic polysaccharide dextran, and the anionic polysaccharides dextran sulphate and propylene glycol alginate (PGA). Tension measurements at the n-hexadecane—water interface are indicative of complex formation with dextran sulphate or PGA, but not with dextran. Emulsions made with simple 1:1 mixtures of protein + polysaccharide (0.5 wt% protein, 10 wt% n-hexadecane) give poorer stability than with protein alone under similar conditions. The presence of unadsorbed polysaccharide gives rapid serum separation due to depletion flocculation. Of the three polysaccharides, PGA gives the largest droplets in the fresh emulsion, but the best stability with respect to coalescence; this is consistent with the formation of a weak protein—PGA complex at the oil—water interface. An attempt has been made to produce strong complexes of β-lactoglobulin with each of the polysaccharides by dry-heating the mixtures at 60°C for up to 3 weeks. This treatment yields a β-lactoglobulin-dextran hybrid which is believed to contain a covalent Maillard-type linkage between the two biopolymers, and which gives emulsions with excellent stability with respect to creaming, coalescence and serum separation. A β-lactoglobulin—dextran sulphate composite produced by the same dry-heating treatment shows little evidence for Maillard-type browning and has poor emulsifying properties. Dry-heating of a mixture of β-lactoglobulin and PGA gives a complex that confers emulsion stability which is at least as good as that for the β-lactoglobulin-dextran hybrid. These results show that protein—polysaccharide emulsifiers with good solubility and excellent emulsion stabilizing properties at pH 7 can be made with food-grade ingredients without the use of chemicals.