Effects of increasing levels of transglutaminase on cooking quality of bran supplemented spaghetti

This study investigated the possibility of incorporating high levels of bran into spaghetti formulation by using transglutaminase (TG)—catalyzed crosslinking, without deterioration in spaghetti quality. Two durum wheat samples and one bread wheat sample were milled to semolina or farina. Ground mixture of coarse and fine brans of each cultivar was substituted for a portion of semolina or farina obtained from the respective cultivar, at the levels of 15 and 30% and then processed into spaghetti. Bacterial TG was added to the spaghetti formula at the levels of 0.2% and 0.4% (w/w). The results indicated that the TOM values and the sensory characteristics of the spaghetti were generally affected by the cultivar, bran supplementation, and TG addition level. The samples with TG exhibited significantly lower scores for TOM and higher sensory scores for firmness, stickiness, and bulkiness when compared with the respective control sample of each cultivar. As a result, transglutaminase addition had a significant improving effect on spaghetti quality which was more obvious in the weaker cultivar and it was possible to overcome the deteriorative effects of bran on spaghetti quality.     

Optimisation of resistant starch II and III levels in durum wheat pasta to reduce in vitro digestibility while maintaining processing and sensory characteristics

Foods with elevated levels of resistant starch (RS) may have beneficial effects on human health. Pasta was enriched with commercial resistant starches (RSII, Hi Maize™ 1043; RSIII, Novelose 330™) at 10%, 20% and 50% substitution of semolina for RSII and 10% and 20% for RSIII and compared with pasta made from 100% durum wheat semolina to investigate technological, sensory, in vitro starch digestibility and structural properties. The resultant RS content of pasta increased from 1.9% to ∼21% and was not reduced on cooking. Significantly, the results indicate that 10% and 20% RSII and RSIII substitution of semolina had no significant effects on pasta cooking loss, texture and sensory properties, with only a minimal reduction in pasta yellowness. Both RS types lowered the extent of in vitro starch hydrolysis compared to that of control pasta. X-ray diffraction and small-angle scattering verified the incorporation of RS and, compared to the control sample, identified enhanced crystallinity and a changed molecular arrangement following digestion. These results can be contrasted with the negative impact on pasta resulting from substitution with equivalent amounts of more traditional dietary fibre such as bran. The study suggests that these RS-containing formulations may be ideal sources for the preparation of pasta with reduced starch digestibility.     

Effect of sodium chloride,sucrose and chestnut starch on rheological properties of chestnut flour doughs

The influence of the addition of NaCl (0.6, 1.2, 1.8%, w/w), sucrose (0.6, 1.8, 3.4, 5.0%, w/w), chestnut starch (5.0, 10.0, 15.0%, w/w) and NaCl–sucrose mixtures (0.6–0.6, 1.8–1.8%, w/w) on the rheological properties of chestnut flour (CF) doughs were studied using a controlled-stress rheometer. Mixing and complete tests were achieved by the Mixolab^® apparatus. Shear (0.01–10 s⁻¹), oscillation (1–100 rad s⁻¹), temperature sweep (30–100 °C) and creep-recovery (loading of 50 Pa) measurements were performed. Steady-flow curves exhibited a Newtonian plateau at <0.1 s⁻¹ that was shifted to lower shear rates with the additives. Apparent viscosities were satisfactorily fitted using Cross model. Moduli values of storage and loss decreased, at constant angular frequency, with increasing additives. Gelatinization temperatures were slightly modified. Creep-recovery data, fitted using Burgers model, showed that the elasticity was low (23.0%) and doughs with chestnut starch presented the highest recoverable proportion (45.6%).     

An approach to modeling the rheological properties of food materials

The aim of this study was to develop a mathematical model describing the rheological properties of food materials, including the elastic modulus, consistency index, flow index and flow limit, that are not dependent on the tests (creep and compression stress relaxation) used to establish those values. A rheological model was designed as a parallel combination of spring, viscous and plastic elements. The model was verified logically and empirically based on the results of creep tests and compression stress relaxation tests performed on 10 × 10 × 10 mm cubes cut out from roasted turkey breast muscles. An analysis of the model’s susceptibility to variations in rheological properties indicates that the model is sensitive to changes in the values of the elastic modulus, flow limit and flow index, but it is less susceptible to changes in the consistency index. The model generates similar values of the rheological properties of the studied materials regardless of whether they had been determined based on the results of the creep test or the compression stress relaxation test.     

Stress relaxation/creep compliance behaviour of kashar cheese: Scanning electron microscopy observations

In this study, uniaxial and creep analyses were used to characterise stress relaxation and creep compliance behaviour of kashar cheese as a function of different compression (1.5, 3.0, 4.5, 6.0 and 7.5 mm) and stress (12.25, 24.50, 36.75, 49.00 and 61.25 kPa) levels. For this purpose, mechanical simulation models, namely generalised Maxwell, Nussinovitch, Peleg and Burger models were used to simulate the viscoelastic behaviour of kashar cheese as a function of different compression and stress levels. The results revealed that the compression levels could remarkably change internal structure and deformation properties of kashar cheese. Stress relaxation test demonstrated that kashar cheese showed more elastic behaviour, namely higher resistance to deformation at higher compression levels. Creep tests showed that rigidity of kashar cheese decreased as the stress level applied increased. Scanning electron microscopy (SEM) images showed that compression resulted in a less homogeneous protein matrix, an interrupted casein/fat network, and destroyed fat globules by forcing them to exude from the cheese surface. These results should be useful for dairy industry.     

Properties of retrograded and acetylated starch preparations Part 2. Dynamics of saccharification with amyloglucosidase and rheological properties of resulting pastes and gels

Various procedures have been used to produce preparations of retrograded starch, by subjecting it to acetylation with methods used in the food industry. The resultant starch preparations were evaluated for their degree of acetylation through titration, swelling power and solubility in water at 80 °C, and saccharification dynamics as affected by amyloglucosidase. Rheological properties of pastes and gels of native starch and modified starch preparations were characterized with the use of a sweep temperature test as a dependency of the storage modulus (G′) and loss modulus (G″) on temperature. In addition, flow curves of pastes were plotted and mechanical spectra of gels of the preparations examined were determined. These modifications had a significant effect on the preparations produced. Retrograded and acetylated starch preparations were characterized by greater solubility in water and greater swelling power, and were less susceptible to amyloglucosidase than the non-acetylated preparations. Rheological properties of the pastes and gels were affected by the methods of their production. Acetylation was found to significantly affect a decrease in the storage modulus value during heating. Pastes of the native starch and modified starch preparations were characterized by the non-Newtonian flow, shear thinning with a tendency to yield stress. In turn, the mechanical spectra demonstrated that - in the concentration applied - both native starch and modified starch preparation were forming weak gels.     

A rheological characterization of semi-solid dairy systems

Dispersions of cross-linked starch in full fat milk, taken as models of custard model systems, have been characterized by different rheological means: viscoelastic measurements, classical flow measurements and ‘vane’ rheometry. From viscosity measurements, the flow behaviour was described within the shear rate range 0.01–100 s⁻¹. The flow curves were fitted using the Herschell–Bulkley equation over the shear rate range 0.1–100 s⁻¹ while a deviation was found towards the low shear rate range, making the determination of the yield stress non realistic. Instead, measurements with the ‘vane’ device in low shear conditions provided a way to estimate the yield stress, at rest and after shearing, but the entire flow curve was not described. From the viscoelastic measurements at low strain amplitude, the mechanical spectra were obtained. Linearity tests beyond the linearity limits provided the critical stress corresponding to the G′–G″ cross-over. The parameters obtained from these different rheological methods are discussed.     

Fine structural characteristics related to digestion properties of acid‐treated fruit starches

Starches from unripe fruits (mango, banana, and plantain) were acid modified to form different degrees of lintners with the objective to increase the slowly digestible starch (SDS) and RS contents. Molecular, thermal, and structural characteristics were evaluated. Mango starch showed higher susceptibility to acid hydrolysis than banana and plantain starches. The peak temperature of gelatinization (T_p) showed a decrease at low hydrolysis percentage, but at higher hydrolysis percentage the T_p increased. However, the enthalpy of gelatinization presented an increase with the hydrolysis percentage, but was not higher than its native counterpart. In general, the peak temperature and enthalpy of retrogradation increased with hydrolysis percentage due to formation of linear chains during the modification that promoted retrogradation. High performance size exclusion chromatography (HPSEC) analysis demonstrated the presence of multiple‐branches (DP = 96–109), single branched (DP = 28–31), and linear (DP = 16–18) polymers in the fruit starch lintners. The acid treatment (lintnerization) of mango starch had no effect on the SDS fraction, while for plantain and banana starches, the SDS content increased (6.14–35.4%) at low hydrolysis percentage (0–50%) followed by a decrease at higher days of hydrolysis. At higher hydrolysis percentage (70–80%) the RS content increased for the three fruit lintners.     

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 10 min 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 7 days 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 1 min OGT. These results show that the extent of starch oxidation varies among starches of different botanical origins under similar ozone treatment conditions.     

In vitro fermentation of different types of α-amylase resistant corn starches

α -amylase resistant corn starches were in vitro fermented (72 h) using cecal content of rat as inoculum. Resistant starches were prepared from native (NCS), retrograded (RS_A ), and retrograded and boiled (RS_B ) corn starch by treatment with α-amylase to remove digestible starch. Short-chain fatty acid (SCFA) production, molar ratios (acetate: propionate: butyrate), fermentability with respect to lactulose and dry matter disappearance were measured. SCFA production was significantly correlated with non-fermented residue (P <0.001). The three starches showed a similar fermentability, although the rate of SCFA production and disappearance of substrate were slower for retrograded starches. NCS was fermented early while RS_A and RS_B prolonged their degradation to 72 h. There were slight differences in the molar ratios of acetate, propionate and butyrate. Structural changes in the materials were observed by scanning electron microscopy (SEM). In summary, commonly utilised domestic cooking and technological treatments modified the in vitro fermentative characteristics of resistant corn starches probably due to structural changes. Received: 15 November 1999 / Revised version: 27 January 2000     

Properties of retrograded and acetylated starch preparations: Part 1. Structure, susceptibility to amylase, and pasting characteristics

The aim of the study was to produce a retrograded starch preparation from potato starch using various methods, to modify it by acetylation, and then to estimate the effect of these modifications on its selected properties. The chemical structure of modifiers and the degree of substitution achieved with acetic acid were determined by nuclear magnetic resonance (NMR). The resistance of starch to amyloglucosidase and digestive amylases was determined as well. Also, the thermal characteristics of gelatinization of the starch preparations were studied by differential scanning calorimetry (DSC); the method of starch paste production was investigated by a Brabender viscograph, and morphological and structural differences were visualized using scanning electron microscopy (SEM). Retrograded starch preparations were porous and stratified in structure; with their properties resulting from the method of their production. Their chemical structure did not differ from that of native starch, but they displayed a different course of pasting characteristics and increased susceptibility to acetylation as well as resistance to amylases (by approximately 10 g/100 g). Acetylation contributed to a decrease in the temperature of reaching maximum viscosity, an increase in the maximum viscosity, and a decrease in the amount of heat needed for thermal transition of the produced preparations. Acetylated retrograded starch was characterized by a higher degree of substitution and an increased activity of acetyl groups substituted at carbon atoms 2 and 3 compared to the acetylated native starch, thereby triggering a significant increase in resistance to amylases (approximately 40 g/100 g). Combining the resistance of starch samples RS3 and RS4 may be a new method to obtain resistant starch from potato starch.     

Viscoelastic characterization of solid foods from creep compliance data: application to potato tissues

 Two software systems were developed to simplify acquisition and analysis of data describing creep behavior of viscoelastic solid foods and to determine the magnitude of instantaneous elastic compliance, viscoelastic compliances and viscosity associated with Newtonian flow. The first of these systems was used to store information on the experiment, to collect the data generated during the experiment, to present these in real time and to create files containing the experimental data for subsequent analysis. The second system was used to fit data to discrete Kelvin-Voigt models with four, six or eight constants. The systems were tested in the calculation of rheological properties of fresh and cooked potato tissues. A six-element Burgers model containing two discrete Voigt units proved the most suitable for defining tissue creep behavior, suggesting that different structural components could be related to each unit. The instantaneous elastic modulus could be associated with internal cell pressure. Gelatinization of starch and viscoelastic units appeared to reflect the viscoelastic properties of pectic substances and hemicelluloses, respectively. Received: 5 March 1998     

Evaluation of four types of resistant starch in muffins. II. Effects in texture,colour and consumer response

In this study, the influence of the addition of four types of resistant starch containing ingredients on texture, colour and consumer acceptability of muffins was studied. Two resistant starch type 2 (RS2) and two resistant starch type 3 (RS3) containing ingredients were used. The addition of all RS types decreased the instrumental texture parameters, but the lowest values were shown by the RS3-containing muffins. No significant differences were found in L* parameter between the control (with no RS addition) and the RS3-containing muffins. On the contrary, RS2-containing muffins showed a lighter colour (L* significantly higher) in comparison to the control and the RS3-containing muffins, which was obvious for the human eye (ΔE* > 3). RS3-containing muffins showed the lowest sensory acceptability while RS2-containing muffins showed no significant differences in all the sensory attributes in comparison to the control.     

The impact of resistant starch on characteristics of gluten-free dough and bread

The study focused on partial replacement in gluten-free breads of corn starch with tapioca and corn resistant starch preparations. The use of resistant starch resulted in the increase of storage and loss moduli of the dough, and the lowering of loss tangent, which indicates its more elastic character. The incorporation of resistant starch reduced creep and recovery compliance and elevated zero shear viscosity. Modified doughs displayed higher starch gelatinization temperatures and lower viscosities that were proportional to the share of RS. It was found that the loaves baked with the share of resistant starch had less hard crumb than bread without RS addition. The crumb hardness diminished with the increasing amount of applied RS preparation. The addition of resistant starch raised total dietary fibre, by up to 89%, as compared to control (bread without RS addition). The most pronounced change was observed for insoluble dietary fibre (increase 137%), while only slight increase was found for its soluble fraction (18%).     

Evaluation of four types of resistant starch in muffin baking performance and relationship with batter rheology

The influence of wheat flour partial replacement with different types of resistant starch (RS) in muffin batter rheological properties and in baked muffin height, volume and number of air bubbles was investigated. The type of RS affected the above-described properties differently. In comparison to the control batter (without RS), replacement with RS type 3 (Novelose 330 and C*Actistar) increased viscosity and viscoelasticity, at both 20 and 80 °C. On the contrary, RS type 2 (Hi-maize 260 and Novelose 240) decreased them. These differences in viscosity and viscoelasticity were related to different baking performance. The RS3 type muffins had higher height, volume and number of air bubbles than the RS2 type muffins. An increase in viscosity and elasticity of the raw batter and during the heating process favours bubble retention and stability, thus favours baking performance. However, despite the improvement provided by the RS type 3, the baking performance was still lower than in the control muffins. One feature that may contribute to the baking differences is the delay in all the RS batters in the starch gelatinization temperature.     

In vitro measurement of resistant starch of cooked milled rice and physico-chemical characteristics affecting its formation

Resistant starch (RS) content was determined in 10 indica and japonica milled rices with different levels of amylose. The effect of microbial growth during starch digestion on the measurement of RS, and the correlation between physico-chemical characteristics and RS contents of milled rice were analysed. Results indicated a significant decrease (P < 0.01) in assay values of RS after antibiotics addition, and the markedly decreased sample pH due to fermentation might be the main reason for errors in RS determination. Correlation analyses showed that RS contents of milled rice were closely related to amylose content (r = 0.75, P < 0.05) and protein content (r = 0.78, P < 0.01). No significant correlation existed between RS content and some relatively simple physical properties, such as width, shape and elongation ratio of rice grain, which were reported to be good indictors of rate of rice starch digestion, while a significant positive correlation was found between elongation ratio and digestible starch in cooked milled rice (r = 0.67, P < 0.05).     

Performance of three different types of resistant starch in fried battered food

Three different types of commercially available RS (one RS type 2 and two RS type 3) were incorporated in a batter formula and their influence on the rheological properties of the raw batter and on the batter pick-up, texture, colour, and consumer acceptability of the final battered fried product were investigated. RS incorporation affected the rheological properties of the raw batter compared with a control (without RS), although no relation between RS type and the flow and viscoelastic properties was found. In comparison to the control batter, replacement of wheat flour with Novelose 330 (RS3 type) increased significantly batter consistency and the values of the viscoelastic moduli G′ and G″, while replacement with both C*Actistar 11700 (RS3 type) or Hi-maize 260 (RS2 type) produced the opposite effect. Instrumental colour was the only property that gave a clear relationship with the type of RS; the two RS3 starches developed a darker colour than the control and the RS2 starch. The RS2 starch showed the best acceptability evaluated by a consumer panel. All the RS types assayed are considered successful to be used in battered food.     

7种淀粉凝胶应力松弛特性研究

将7种淀粉采用相同方法制备出凝胶块作为实验试样,经质构仪进行压缩和应力松弛实验得到流变学特性参数。利用统计分析软件进行非线性回归拟合,建立了广义Maxwell力学模型。结果表明:淀粉凝胶具有良好的压缩黏弹性力学性质,五元件广义Maxwell模型适用于模拟淀粉凝胶的应力松弛现象。通过主成分分析,应力松弛参数可归纳为两类,即凝胶粘弹特性和凝胶松弛时间。