Optimisation of conditions for precipitation of collagen from solution using κ-carrageenan. Studies on collagen from the skin of Baltic cod (Gadus morhua)

The effects of the concentration of collagen (0.025–3%), extracted from the skins of Baltic cod (Gadus morhua) and the concentration of κ-carrageenan (0.04–1%), in the presence of NaCl (0–5%), on the yield of precipitated collagen fibrils at 0 °C and at pH 2.2–8 were determined. The yield of precipitated collagen was directly proportional to the ratio, κ-carrageenan to collagen, within the range 0.015–0.4. Collagen dissolved in citric acid could be completely precipitated using κ-carrageenan if the weight ratio of dry reagents was 1:0.4 within a protein concentration of 1.5–0.08%. The maximal yield of precipitated collagen fibrils using κ-carrageenan could be achieved in the pH range 2.2–3. In this range of pH, the presence of NaCl in the system did not affect the efficiency of precipitation of collagen fibrils with κ-carrageenan. The yield of precipitated collagen was lower at 20 °C than at 0 °C.     

Rheology of Sol-Gel Thermal Transition in Cowpea Flour and Starch Slurry

A thermal scanning rigidity monitor was used to follow rheological changes during heating of cowpea flour and starch slurries. The gelantinization temperature of cowpea starch was in the range 67–78°C. For cowpea flour, in addition to starch gelatinization, a shallow plateau was observed. The starch gelatinization onset temperature shifted from 67°C for starch to 72C for 25% cowpea flour that contained 12–15% starch. The modulus (G′) of cowpea gels increased with flour concentration according to a power relationship. Rigidity of the cowpea starch and flour gels decreased at temperatures higher than 78 and 87°C, respectively.     

Thermal and rheological properties of hydrogels prepared with retrograded waxy rice starch powders

Waxy rice starch dispersed in water (50% solids) was gelatinized by heating the dispersion at 121°C for 20 min, and retrograded by storing the paste at 4°C for 2 days. The starch gel was then freeze-dried and ground into powders. The retrograded starch powders were hydrated at 20–30% solid concentration at different temperatures (4 and 23°C), and then thermal and rheological properties were analyzed using the hydrogels. The gel hydrated at 4°C had an onset temperature of melting at 34.9°C, which was approximately 10°C lower than that observed for the gel hydrated at 23°C. The enthalpy value was greater for the gel hydrated at 4°C (14.2 J/g) than the gel hydrated at 23°C (8.8 J/g). The yield stress and consistency of the hydrogels were proportional to the solid concentration. The hydrogel prepared with 30% retrograded starch powders at 4°C displayed a thick creamy texture with retrograded starch crystals that could melt at a temperature range of 35–51°C. The thermal and rheological properties of the hydrogels exhibited the possibility for the retrograded starch powders to be used as fat mimetic in foods.     

GELATION KINETICS of MEAT EMULSIONS CONTAINING VARIOUS FILLERS DURING COOKING

A cylindrical shaped thermal scanning rigidity monitor (TSRM) was developed to determine shear rigidity modulus of meat batters during cooking. A meat fatprotein ratio of 1.8, moisture content of 62% and 8.6% filler were used. the fillers were buttermilk powder, corn starch, micro-crystalline cellulose, modified corn starch, modified wheat flour, soy-protein concentrate and whey-protein concentrate. Plots of rigidity modulus versus product-temperature showed two major thermal transitions. the first and most important transition (53 to 61°C) was due to myosin gelation. the second transition (64 to 69°C) was ascribed to the collagen softening. the maximum rigidity-temperature slopes of 0.60 to 1.02 kPa/°C occurred after the first transition.     

Alkali Extraction of Starch from Corn Flour

The alkali steeping process was tested for extraction of starch from degerminated yellow corn flour. The effect of three process parameters, alkali concentration (0.1 and 0.4%), steep temperature (25 and 55°C) and steep time (30 and 90min) were evaluated for their effect on yield, protein and sodium contents of starch. Two-level full factorial design was used to investigate the process. The experimental results indicated that starch yield increased with increasing steep temperature and at low alkali concentration. All main effects and interactions were found to have significant effect on protein content in the extracted starch. The sodium content of the starch was effected by the three main effects and the three two-factor interaction effects. Conditions were identified that simultaneously produced a high starch yield, low protein and sodium contents were 0.1% alkali steep at 55°C for 30 min.     

Thermal Processing of Cowpea Slurries

Isochronal temperature profiles of 20% cowpea flour slurries showed conduction heating while the estimated Rayleigh numbers predicted natural convection heating; apparently, the flour particles suppressed convection. Magnitudes of f_h of cowpea gels increased linearly with fat content, decreased with moisture content, and were independent of the cowpea flour particle size. The heating curve of a 10% cowpea flour slurry at 121°C showed one break due to gelation of protein and starch at about 66°C and another due to loss of rigidity at about 87°C.     

The performance of a methyl cellulose-treated coating during the frying of a poultry product

The performance of coatings treated with a range of methyl cellulose (MC) concentrations during the frying of coated chicken breasts was investigated. Chicken breasts were immersed in 0, 1 and 2.5% MC solution and then coated with a commercial coating mix. The coated chicken breasts were then fried at an initial temperature of 190 °C. Parameters measured included coating pickup, coating loss, cooked yield and frying loss. Results showed a significant increase in coating pickup with the use of 1 and 2.5% MC, which may have been due to the higher viscosity and binding ability of the MC layer. The use of 2.5% MC produced lower coating loss and frying loss and also a higher cooked yield.     

温敏型胶体对玉米淀粉3D打印固化性能的影响

目的:利用温敏型胶体的相转变特性,辅助实现淀粉在打印过程中的成型固化,并揭示不同种类胶体-淀粉体系的固化性能变化规律。方法:将不同比例的温敏型胶体(低酰基结冷胶、明胶、κ-卡拉胶)与玉米淀粉进行复配并测定其流变性能,通过打印圆柱及空心球模型、测试产品力-位移曲线、温度扫描流变、全质构分析及微观结构观测评估体系可打印及固化性能。结果:结冷胶和卡拉胶在2%～4%添加量,明胶在0%～2%添加量时,体系具有适宜的流变性能及良好的可打印性能。添加4%结冷胶及4%卡拉胶的产品表现出显著的塑性,固化效果较好;添加明胶的打印产品无显著塑性,打印产品不固化。结冷胶-淀粉混合体系的固化温度在35～43℃之间;卡拉胶-淀粉混合体系的固化温度在30～40℃之间,随着胶体含量增加,固化温度上升,固化速度加快。而随着明胶含量增加,固化温度从25℃下降至20℃以下且固化速度减慢。4%低酰基结冷胶产品具有更致密的凝胶网络,硬度高于4%κ-卡拉胶产品。明胶对硬度、弹性都有削弱作用,但使粘附力大幅提高。结论:适宜含量的低酰基结冷胶和κ-卡拉胶能够实现淀粉的成型固化,且卡拉胶固化性能优于结冷胶,而明胶则无辅助固化能力。     

Effect of acid‐ethanol treatment followed by ball milling on structural and physicochemical characteristics of cassava starch

Structural and physicochemical characteristics of cassava starch treated with 0.36% HCl in anhydrous ethanol during 1 and 12 h at 30, 40, and 50°C followed by ball milling for 1 h were analyzed. Average yield of acid‐ethanol starches reached 98% independent of the treatment conditions. Solubility of acid‐ethanol starches increased with reaction temperature and time, but it did not change after ball milling. Granule average size reduced with chemical treatment from 25.2 to 20.0 µm after 12 h at 50°C. Ball milling decreased the granule average diameter of the native starch and those chemically treated at 30°C/1 h or 40°C/1 h, but it did not alter the starches treated for 12 h, independent of temperature. From scanning electron microscopy (SEM), starch granules presented round shape and after modification at 50°C/12 h, before and after ball milling, showed a rough and exfoliated surface. Some granules were deformed, suggesting partial gelatinization that was more intense after milling. Starch crystallinity increased as temperature and time of chemical treatment were increased, while amylose content, intrinsic, and pasting viscosities decreased. Gelatinization temperatures increased for all chemical starches. The findings can be related to the preferential destruction of amorphous areas in the granules, which are composed of amylose and amylopectin. After ball milling, the starch crystallinity decreased, amylose content, intrinsic, and pasting viscosities kept unchanged and gelatinization temperatures and enthalpy reduced. Ball milling on native and chemical starches caused the increase of amorphous areas with consequent weakening and decreasing of crystalline areas by breaking of hydrogen bonds within the granules.     

Rheological Characteristics of Halberd Wheat Starch

The non‐Newtonian behavior and dynamic viscoelasticity of Halberd wheat starch (23.0% amylose content) pastes were determined with a rheogoniometer. The flow curves, at 25°C, of Halberd starch pastes showed plastic behavior at concentrations of more than 4.0%. The shear viscosity of the starch pastes decreased gradually with an increase in temperature at concentrations less than 4.0%, but remained constant at a concentration of 5.0%. The storage modulus of the starch pastes increased with increasing concentration and remained high during increase in temperature up to 80°C. Almost the same storage modulus was observed upon addition of urea (4.0 M) to the paste at low temperature (0°C), and the modulus stayed at a large value with increase in temperature up to 60°C, which was estimated to be a transition temperature; then it decreased rapidly with further temperature increase. A transition temperature of 60°C was also observed in the dynamic viscosity. A very large storage modulus and dynamic viscosity were observed in alkaline solution (0.05 M NaOH) at low temperature (0°C), both quantities decreased slightly with increase in temperature up to 25°C, which was estimated to be a transition temperature, then decreased rapidly with further increase in temperature. A possible intermolecular hydrogen bonding between amylose and amylopectin molecules is proposed.     

Preparation of Long-chain Esters of Starch Using Fatty Acid Chlorides in the Absence of an Organic Solvent

An efficient method of synthesizing fatty acid esters of starch without organic solvents is described. The octanoate of starch was prepared by gelatinization of native starch with formic acid, followed by treatment with octanoyl chloride. Esterification was readily carried out under a stream of N₂ at a stirring rate of 500 min ^-1 at 25—130°C for a reaction duration of 20—120 min. Formic acid enabled esterification of starch by long-chain acyl chlorides with minimum degradation. The major factors affecting the esterification reaction were optimized. The results indicated that the octanoyl degree of substitution (DS₈) was increased with increase in fatty acid chloride concentration (from 3—12 eq. per anhydroglucose unit) and rise in temperature (25°C to 130°C). Higher octanoyl chloride concentrations and temperatures led to a reduction in yield due to acid hydrolysis of starch chains. A maximum DS₈ of 1.7 was reached after 40 min of reaction, and high concentrations of formic acid decreased the octanoyl substitution. On the other hand, higher concentration of octanoyl chloride, higher temperatures and longer reaction times increased the substitution of the long acyl chain into starch.     

Thermal,microscopic, and quality properties of low-fat frankfurters and emulsions produced by addition of different hydrocolloids

This study involves investigation of the effects of addition of different hydrocolloids on the thermal, microscopic, and quality properties of low-fat meat emulsions and frankfurters. The emulsion stability of the samples containing 0.5% κ-carrageenan, λ-carrageenan or chitosan, and the 1% chitosan containing sample were lower than that of the control group. Thermal analyses showed three denaturation peaks for minced meat at 57.42 °C, 64.21 °C and 78.58 °C. While the denaturation temperature of myosin for the sample produced with 0.5% of κ-carrageenan was significantly lower, samples containing 1% κ-carrageenan and 0.5% λ-carrageenan were not significantly different than that of the control group. The thermal denaturation temperature of myosin for samples containing 1% λ-carrageenan, and for 0.5% and 1% guar gum, xanthan gum and chitosan was significantly higher than that of the control. The denaturation temperature of sarcoplasmic proteins and actin for samples with 1% κ- and λ-carrageenan and 0.5% chitosan, was higher than for the control, while for other samples it was not significantly different. The scanning electron microscopy images of the control group and samples produced with 0.5% and 1% λ-carrageenan, 0.5% and 1% guar gum, and 1% κ-carrageenan showed gel-like structures, whereas other samples did not. Sensory evaluations showed that addition of hydrocolloids and reduced fat content lowered acceptance of frankfurters. Results showed that both κ- and λ-carrageenan, especially at 0.5% were the most suitable hydrocolloids for production of low-fat frankfurters and xanthan gum was the least suitable since it did not form proper structure.     

紫山药抗消化淀粉的制备及水解特性*

以酶解-压热法制备紫山药抗消化淀粉,考察了淀粉乳浓度、普鲁兰酶用量、酶解时间、压热时间对制备淀粉中抗消化淀粉含量的影响,通过正交试验和方差分析明确影响因素的重要性并优化工艺条件;比较分析了糊化淀粉、压热淀粉以及酶解-压热法制备淀粉的水解动力学。结果表明:酶解-压热法制备紫山药抗消化淀粉的含量随各因素水平的增加呈先增加后减小的趋势,优化的条件为:淀粉乳质量分数20%、普鲁兰酶用量8 U/g、酶解12 h、以120℃压热处理40 min 2次时,制备抗消化淀粉样品纯度为96.67%,其中抗消化淀粉含量为47.85%;水解特性研究表明:与糊化、压热法相比,酶解-压热法制备抗消化淀粉的水解率、水解指数与血糖指数均显著降低,具有更好的抗消化性。     

Preparation and rheological properties of a dairy dessert based on whey protein/potato starch

Gels were prepared by heating different mixtures of whey protein concentrates (WPC) potatoes and ι-carrageenan. The influence of these ingredients on the strength of the obtained gels was investigated. The rheological properties of these gels were also measured during cooling from 90 to 10 °C at variable frequencies and strains. Analysis of variance showed a highly significant (P<0.0001) relationship between the concentrations of the different ingredients and the gel strength. The storage modulus (G^′) was generally higher than the loss modulus (G″) at different temperatures. Generally, the log (G^′) and log (G″) increased with the increase in the applied frequency, which suggested a weak gel entanglement network. Desserts were also prepared using 4% WPC and 3% potato starch (PS), 0.1% ι-carrageenan, 10% sucrose, 3% milk fat and 3% cocoa powder, by heating at 100, 110 or 120 °C for 30 min, packaged hot and stored for 28 days at room temperature (20 ± 5 °C). Samples of fresh and stored desserts were taken at 0, 7, 14, 21, 28 days of storage and their gel strengths were measured. Also, the effect of heat treatment during preparation on G^′, G″ and phase angle (δ) of the different desserts was followed. The effects of the heating time and temperature on the gel strength and rheological properties were relatively small.     

Gelatinization Properties of Navy Bean Starch

Gelatinization properties of navy bean (Phaseolus vulgaris) starch under different combinations of concentration (6, 8, 10 and 12%) and cooking temperature (75, 85 and 95°C) were studied using a rotational viscometer. The torque response due to swelling and/or breakdown of starch granules approached equilibrium after either a gradual increase or a relatively rapid increase to a peak followed by a decline during cooking. For every condition, the difference between the final torque values obtained for the rapid and the slow heating processes was not significant. In general, the viscosity of the paste increased as the starch concentration and/or cooking temperature increased. However, cooking temperature of 75°C did not cause a significant gelatinization or swelling of starch granules in pastes of 6 or 8% concentration. Maximum final viscosity values were obtained at 85°C for all starch concentrations except for a maxium at 95°C for 6%. Thixotropic breakdown was observed at 10 and 12% concentrations during initial shearing at 85 and 95°C. The threshold concentration for singnificant viscosity effects in this study was in the range of about 8 to 10% or 95°C. The calculated activation energy (14.5 Kcal.g⁻¹ mole⁻¹) of navy bean starch gelatinization was similar to values reported for rough rice and rice starches.     

Effect of Molar Substitution on Rheological Properties of Hydroxypropylated Rice Starch Pastes

The steady and dynamic shear rheological properties of hydroxypropylated rice starch pastes (5%, w/w) were evaluated at different molar substitution (MS, 0.030‐0.142). The swelling power (35.5‐52.8 g/g) and solubility (8.19‐10.7%) values of the hydroxyproylated rice starches were higher than those of native rice starch (26.6 g/g and 7.78%) and increased with an increase in MS. The hydroxypropylated starch pastes at 25°C showed a pronounced shear‐thinning behavior (n = 0.33‐0.40) with Casson yield stress (σ_oc = 15.9‐31.7 Pa). The consistency index (K) and yield stress (σ_oc) values of the hydroxypropylated starch pastes were lower than those of the native starch, and increased progressively with an increase in MS. The apparent viscosity (η_a,500) obeyed the Arrhenius temperature relationship over the temperature range of 10‐55°C; the activation energies (E_a) of the hydroxypropylated starch pastes were in the range of 14.8‐18.5 kJ/mol, i.e. higher than that (14.1 kJ/mol) of the native starch. Storage (G′) and loss moduli (G′′) of hydroxypropylated starch pastes increased with an increase in MS, while tan δ (G′′/G′) values decreased, indicating that G′ rose more strongly than G′′ with increased MS.     

Low-fat sodium-reduced sausages: Effect of the interaction between locust bean gum, potato starch and κ-carrageenan by a mixture design approach

A mixture design approach was used to evaluate interactions between potato starch, locust bean gum and κ-carrageenan and their effect on cooking yield, expressible moisture, texture and color in low-fat sodium-reduced sausages formulated with potassium and calcium chloride. Starch had a notable influence on cooking yield and texture, increasing product hardness and resilience as starch proportion increased. The added salt did not allow complete starch granule gelatinization and swelling, which negatively affected water retention, cohesiveness and lightness. Locust bean gum and κ-carrageenan improved cooking yield and reduced expressible moisture in formulations containing higher proportions of potato starch. The presence of other ions could have enhanced κ-carrageenan functionality and its synergistic interaction with locust bean gum, improving texture and water retention, with only minor effects on sausage color. At the lower tested proportions starch can be used as an extender in low-fat cooked meat products if κ-carrageenan and locust bean gum are included in similar proportions.     

Phase separation in soft-serve ice cream mixes: rheology and microstructure

Soft-serve ice cream mixes containing 4% milk protein and 0.14% locust bean gum (LBG) showed extensive visual phase-separation after 21 days at 5 °C, unless κ-carrageenan was added to the formulation. Addition of κ-carrageenan (0–0.02%) did not inhibit microscopic phase separation between protein and polysaccharide. A higher degree of “emulsification” of the protein-enriched phase into the continuous serum phase was observed as the κ-carrageenan concentration increased, which correlated with inhibition of macroscopic serum separation in the mix. After macroscopic separation, the serum phase of mixes with different κ-carrageenan concentrations showed similar microstructural and rheological characteristics, implying no concentration of LBG and no presence of κ-carrageenan in the serum phase. The rheological behaviour of the protein-enriched phases indicated κ-carrageenan/casein interactions. There was no evidence of “weak-gel” formation through the addition of κ-carrageenan as a means for macroscopic stability in the system.     

Restructuring of Mechanically Deboned Chicken and Nonmeat Binders in a Twin-screw Extruder

A twin-screw cooking extruder was used to restructure mechanically deboned chicken (MDC) in combination with three nonmeat binders, corn starch (CS), soy protein isolate (SPI) and wheat gluten (WG), at concentrations of 10–30%. Extrudates were evaluated by apparent tensile stress (ATS), Warner Bratzler shear stress (WBSS), proximate composition and reheat yield. SPI and WG were less effective than starch for increasing the ATS and WBSS of extruded MDC. The effects of die temperatures between 71–115°C on chemical and textural properties of extrudates containing 10% and 15% starch were investigated. The ATS and WBSS increased as a function of temperature up to 104°C. Fat content and lipid oxidation decreased as extrusion temperatures increased.     

Viscosity and Gelatinization Characteristics of Hydroxyethyl Starch

Viscosity and gelatinization characteristics of corn and potato starches as well as their hydroxyethyl derivatives were investigated. The inherent viscosity increased from 164 in native corn starch to 209 in etherified one of DS 0.18. The etherified corn starch gelatinized at lower temperature than native corn starch due to their increase of DS. Maximum viscosity decreased from 93°C to 69°C for the modified corn starch. The retrogradation of starch was minimized by etherification as retrogradation ability of corn starch from its solution decrease from 22% to 6%. This is of great importance when starch is used as blood plasma volume expander. Variable results were obtained with etherified potato starch which might be due to its high contents of phosphorus.