Physicochemical Properties of Casein‐Starch Interaction Obtained by Extrusion Process

Extruded samples of starch‐casein blends were processed by using a single‐screw extruder. The independent variables in the process were temperature (126–194°C), moisture content (18–29%) and starch‐casein blend (5–95%). These independent variables affected significantly the physicochemical and textural properties of the biopolymers. The highest values for expansion (EXP) and water absorption index (WAI) were found when a higher starch proportion was present in the blends, at 126°C barrel temperature and moisture content higher than 25%. By increasing the barrel temperature, from 126°C to 194°C, the water solubility index (WSI) and color parameter were increased. Initial viscosity (IV) and viscosity at 90°C (V90) were mainly affected by the barrel temperature at 194°C. However, the viscosity at 50°C (V50) was affected neither by the different extrusion variables nor by the biopolymer proportion in the blends. Compression force (CF) was strongly dependent on moisture content and casein proportion in the blend. The higher CF values were found at starch concentrations around 50% and 25% moisture content, for higher or lower values than these the obtained extruded products were softer and consequently had lower CF values.     

Effect of Enzymatic Hydrolysis of Wheat Starch on Amylose‐Lipid Complexes Stability

In the process of enzymatic hydrolysis of wheat starch to glucose, the presence of amylose‐lipid complexes (AML's) decreases swelling and dissolving capacity and the water binding capacity of starch, thus impeding the access of amylolytic enzymes to the starch granules. The aim of the work was to define the relationship between the stability of AML's and the conditions of the enzymatic hydrolysis of wheat starch such as the kind of enzymatic preparation (only amylolytic or both amylolytic and lipolytic) and time of hydrolysis. Hydrolysates were produced from wheat starch liquefied with bacterial α‐amylase BAN 240L, subjected to further treatment with the enzymatic preparation Spezyme GA 300W, containing glucoamylase and lysophospholipase and, for comparison, only with a glucoamylase preparation (AMG 300L). The effect of amylolytic and lipolytic enzymes on the stability of AML's in the process of wheat starch hydrolysis was estimated. The amount of fatty acids released during hydrolysis was determined with gas‐liquid chromatography (GLC) and by differential scanning calorimetry (DSC) measuring the enthalpy of decomposition of AML's. The investigations revealed a differentiated effect of the individual enzymatic preparations on the degree of degradation of AML's. Amylose‐lipid complexes were more susceptible to the attack of preparation Spezyme GA 300W than to the digestion by α‐amylase BAN 240 L and glucoamylase AMG 300L.     

Impact of Pre‐Processing of Montmorillonite on the Properties of Melt‐Extruded Thermoplastic Starch/ Montmorillonite Nanocomposites

A simple and environmentally‐friendly processing method was used to prepare thermoplastic starch (TPS)/ montmorillonite (MMT) nanocomposites. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) demonstrated that glycerol could enlarge the d‐spacing and destruct the layered structure of MMT effectively during the pre‐processing of MMT. So the enlarged d‐spacing and fragmentized platelets of glycerol activated‐MMT were a precondition to form intercalated or exfoliated TPS‐based nanocomposites during the melt extrusion processing. These highly dispersive and compatible TPS/activated‐MMT nanocomposites had increased thermal stability and tensile properties as compared with non‐activated composites. Especially, the tensile strength of nanocomposites could be enhanced to 8.6 MPa, the improvement was about two times the initial tensile strength of TPS.     

Starch Properties in Different Lines of an old Hungarian Wheat Variety,Bánkúti 1201

The old Hungarian wheat variety, Bánkúti 1201 was previously divided into lines on the basis of high molecular weight (HMW) glutenin subunit composition. In this work the starch properties of these lines were studied. The amylose contents of the lines ranged from 14.4% to 24.2%, which means a wide variation. The Rapid Visco Analyser (RVA) peak viscosity of the starch ranged from 232 to 372 Rapid Visco Units (RVU) and the enthalpy of gelatinisation (ΔH) measured by Differential Scanning Calorimetry (DSC) varied between 8.3 and 16.3 J/g. To study the relationship between the different lines on the basis of starch properties, Hierarchical Cluster Analysis was carried out based on RVA, DSC and HPLC results. Five groups of Bánkúti lines could be distinguished on the basis of these traits. According to the results, Bánkúti lines heterogeneous with respect to their HMW glutenin composition are also heterogeneous for their starch properties. Nevertheless, there was no correlation between the variability in protein composition and starch properties.     

Laboratory‐scale Dry/Wet‐Milling Process for the Extraction of Starch and Gluten from Wheat

A laboratory‐scale process is presented for the manufacture of starch and gluten from wheat. Main feature of this process is that whole wheat kernels are crushed dry between smooth rolls prior to wet disintegration in excess water in such way that gluten formation is prevented and fibres can be removed by sieving. Centrifugation of the endosperm suspension yields a dough which can be separated into starch and gluten using an established batter process. The results suggest that starch recovery is increased in comparison to a conventional wheat flour process without a concomitant decrease in protein recovery. Although starch purification was omitted, a total starch with a low protein content is obtained. On the other hand, the protein content of the gluten fraction is rather low due to difficulties in removing the starch. Despite this, the effect on dough mechanical properties by the addition of gluten obtained from wet‐milled wheat is comparable to the effect of gluten from flour.     

Effects of Granule Sizes on Physicochemical Properties of Cross‐linked and Acetylated Wheat Starches

Large and small wheat starch granules were used for cross‐linking and acetylation to determine effects of granule sizes on physicochemical properties of the modified starches. The native and cross‐linked starches from the small granules showed higher phosphorus contents than did those from the large granules. However, the level of phosphate substituents in the modified starches was not significantly different between the large and small granules under the same conditions. In contrast, the large granules had a higher reactivity with acetic anhydride than did the small granules. The phosphate group cross‐linked starch (CS), acetylated starch (AS) and acetylated cross‐linked starch (ACS) from the large granules had lower gelatinization temperatures and higher enthalpies than those from the small granules. The paste viscosities of the CSs from the large granules decreased rapidly, whereas those of the AS or ACS increased significantly as compared with those from the small granules. The pastes of cross‐linked starches from the small granules were more stable than those from the large granules, whereas the pastes of AS and ACS from the large and small granules had similar resistance to freeze‐thaw treatment. Scanning electron microscopy (SEM) also showed that the small granules were less damaged after modification than the large ones. Thus, the different granule sizes resulted in different physicochemical properties of starch after modification.     

Ghosts of B‐type Wheat Starch Granules in Concentrated KI/I2 Solution

When B‐type (2.0–8.0 µm) wheat starch granules containing various amounts (2.1–25%) of amylose were treated with 25% KI/10% I₂ solution, low‐amylose (below 10% amylose) B‐type wheat starch granules changed to the ghost form. It is known that A‐type (25–35 µm) wheat starch granules change to the ghost form and show a typical double structure (a black‐brown central portion and red‐brown surrounding portion), however, the B‐type wheat starch ghosts did not show the same double structure but rather a simple (red‐brown portion) sack form. The relative ghost areas in the B‐type wheat starch granules were highly correlated to the amylose content (%), which was similar to the results of A‐type starch granules. This suggests that the amylose molecule in B‐type starch contributes to the structural stability of the starch granule.     

小麦淀粉加工工业废水处理研究进展

小麦淀粉加工工业产生大量的高浓度有机废水，直接排放对环境造成极大的污染。文中介绍了此废水的产生逢径．对此废水进行处理的必要性和意艾；详细介绍了谊废水处理方法的研究进展，如生物法、蒸发法、化学絮凝法等．总鲒了这些方法的不足之处，提出了将膜技术用于此领域的巨大潜力。     

Physical and Mechanical Properties of Durum Wheat (Triticum durum) Starch Films Prepared with A‐ and B‐type Granules

The use of starch for the production of biodegradable materials has been increasing. Wheat is an important source, however, durum wheat starch and its separated granular components had not been evaluated for this purpose. The aim of this study was to evaluate the physical and mechanical properties of durum wheat starch films when prepared with a distribution of different granular‐sized starches (A‐ and B‐type). Starch was isolated, and the A and B populations of granules were separated. Films were prepared by casting. Glycerol (G) was used as a plasticizer in concentrations of 25% and 40%, respectively. Starch films were evaluated using scanning electron microscopy (SEM), mechanical properties (tensile strength, TS, elongation at break, E, elastic modulus, EM), solubility, and X‐ray diffraction (XRD). Durum wheat starch films were transparent, flexible, and, according to SEM, highly homogeneous. Films prepared with 25% G showed brittle material behavior (TS = 42–50 MPa, E = 1.4–2.7%, and EM = 31–34 MPa), whereas those prepared with 40% G had ductile material characteristics (TS = 11–17 MPa, E = 4–41%, and EM = 4–11.3 MPa). These mechanical properties of the films were significantly affected by the glycerol concentration and the starch granule type used. The film solubility was low when compared to those reported in other studies. It increased with increasing plasticizer concentration. According to the XRD, the films showed a semi‐crystalline structure.     

Dependence of Thermodynamic Characteristics of Amylose‐Lipid Complex Dissociation on a Variety of Wheat

Native wheat starch contains amylose‐lipid complexes (AMLs) that are formed both upon biosynthesis of native starch and upon heating of starch slurries at gelatinization temperature and above. These complexes have a detrimental impact on physicochemical properties of starch, because they reduce water binding by starch granules and retard their swelling. An objective of the presented work was to analyze the chemical composition of wheat starch and characterize the thermodynamics of gelatinization of different wheat starches and to evaluate the stability of AMLs derived from these starches with the aid of differential scanning calorimetry (DSC). Grains of eight wheat varieties were used throughout the studies. The gelatinization behavior of the eight wheat varieties examined was similar. The lowest temperature of the onset of gelatinization (T_k = 57.07°C) was found for the Jawa variety, and the highest (T_k = 60.58°C) for the Torka variety. Enthalpy of gelatinization (ΔH_k) of the examined wheat starch preparations ranged from 9.14 J/g (Sakwa) to 11.95 J/g (Elena). Temperature and enthalpy of AMLs dissociation depended on wheat starch variety. During the first heating the temperature of the minimum of the endotherm (T_d) ranged from 98.41°C to 100.5°C. During the second heating, the minimum was at slightly higher temperatures, varying from 102.02°C to 104.08°C. Enthalpies of AML dissociation (ΔH_d) varied from 1.45 J/g to 2.14 J/g during the first heating. During the second heating the enthalpy values were slightly lower (1.26 J/g to 1.68 J/g). Enthalpies of AML reassociation ranged from 1.29 J/g to 1.72 J/g during the first cooling, and from 1.17 J/g to 1.63 J/g during the second cooling. A correlation was found between the amount of lipids and AML content.     

Influence of Jet‐Cooking Temperature and Ionic Strength on Size and Structure of Cationic Potato Amylopectin Starch as Measured by Asymmetrical Flow Field‐Flow Fractionation Multi‐Angle Light Scattering

Asymmetrical flow field‐flow fractionation (AsFlFFF) in combination with multi‐angle light scattering (MALS) was applied to cationic potato amylopectin (CPAP) to investigate how molar mass, root‐mean‐square (r.m.s.) radius and shape was influenced by different conditions of jet‐cooking. The effect of different jet‐cooking temperatures in the range 110°C – 140°C was studied in an excess steam jet‐cooker. This equipment is used in the industry for dissolution of starch and starch derivatives before technical application. The effect of different ionic strengths conditions was examined in the range of 10–200 mM. The weight‐average molar mass decreased from about 34×10⁷ g/mol to 2.6×10⁷ g/mol when the jet‐cooking temperature was increased from 110°C to 140°C. Concurrently the root‐mean‐square radius decreased from ca 380 nm to 90 nm. The decrease in size was reflected by a decrease in viscosity with increasing temperature. The root‐mean‐square radius was reduced when increasing the ionic strength. This decrease in size was correlated with a decrease in viscosity. Conformation and Kratky plots showed that at low ionic strength (≤ 10 mM) CPAP behaved as a flexible chain with high degree of branching, close to hyperbranching. Increase of the ionic strength gave a more compact structure and changes in the internal structure were observed as well. Consequently, by using AsFlFFF – MALS the effect of technical processing on the molar mass, molecular radius, conformational structure, and shape could be determined in a size region where standard methodology commonly fails.     

Influence of Gluten and Gum Additives and Cryogenic Treatment on Some Properties and Morphology of Wheat Starch Complex Gels

The influence of gums (guar and xanthan) and gluten additives on the physicochemical properties and structural features of wheat starch gels (8%, w/w) subjected to cryogenic treatment at various temperatures (−9°C, −20°C, −40°C) was studied. Shear modulus and breaking stress of the gels were measured, the gels' morphology was studied with optical microscopy and the local mobility of water in the gels was determined with ESR. The total concentration of polysaccharide additives did not exceed 1% (w/w), and a 65:35 (w/w) mixture of guar and xanthan gums proved to be the optimal additive, which caused a noticeable increase in rigidity and strength of the resulting complex gels. Shear modulus and breaking stress of the gels decreased with lowering the temperature of the cryogenic treatment. The heterogeneous morphology of thin sections of the gel samples was revealed via optical microscopy. ESR studies showed that the local mobility of water was much lower in the gels than in pure water.     

Influence of Selected Parameters of Starch Gelatinization and Hydrolysis on Stability of Amylose‐Lipid Complexes

Dissociation of amylose – lipid complexes (AMLs) upon gelatinization and enzymatic hydrolysis of wheat starch has been examined using differential scanning calorimetry (DSC). Digestion of starch by the thermostable α‐amylase THERMAMYL 120L was carried out under conditions applied for enzymatic hydrolysis of wheat starch in industry, i.e. 5 min incubation at 105°C, followed by 60–90 min hydrolysis at 95°C. For comparison reasons, samples of wheat starch slurries were incubated under the same conditions but in the absence of enzyme. The enthalpy and temperature of AMLs dissociation and the shapes of peaks in the DSC endo‐ and exotherms depended on conditions of starch processing prior to DSC measurements. Wheat starch gelatinization coupled with its digestion by α‐amylase resulted in more pronounced AML degradation as compared to gelatinization in the absence of enzyme. Different shapes of peaks in thermograms and different temperatures of AMLs dissociation and reassociation indicate that different AML polymorphs were generated in the examined samples. Their concentrations depended on conditions (temperature, time and the presence or absence of α‐amylase) of wheat starch treatment.     

Influence of Citric Acid on the Properties of Glycerol‐plasticized dry Starch (DTPS) and DTPS/Poly(lactic acid) Blends

In the presence of citric acid (CA), one‐step extrusion processing is used to prepare poly(lactic acid)/thermoplastic dry starch (PLA/DTPS) blends (50/50, %, w/w) in a single‐screw extruder. The rheological study proves that CA decreases the viscosity of both DTPS and of DTPS/PLA blends. The low viscosity increases the dispersion and decreases the interfacial tension between DTPS and PLA, as shown by scanning electron microscopy (SEM). In the presence of CA, the tensile strength of DTPS/PLA reaches 41 MPa—similar to that of pure PLA—because of improved dispersion and compatibility. At the same time, CA increases not only the degradation of starch, but also the interaction between DTPS and PLA, as detected by Fourier transform infrared (FTIR) spectroscopy. The blend containing CA has a higher thermal stability. The water absorption of DTPS and DTPS/PLA blends is also studied.     

Effectiveness of Rinse Water during In‐Place Cleaning of Stainless Steel Pipe Lines

The 1st step of any Clean‐In‐Place (CIP) operation is a prerinse with water. The purpose of this step is to remove the bulk of food material remaining in the processing lines after production period has ended. It is known that this prerinse step can be a very water intensive process. The objective of this investigation was to measure the influence of CIP parameters (flow characteristics, water temperature, and contact time) on the effectiveness of prerinse water in removing dairy‐based deposits from stainless steel pipe surfaces and to compare the rinse effectiveness of unused to reused rinse water. A pilot‐scale CIP system was operated to rinse 304 stainless steel pipe sections of 3 different pipe diameters. The velocity of the rinse water was varied from 0.72 to 2.26 m/s. The rinse water temperatures were 22 °C, 45 °C, and 67 °C. The contact times between rinse water and deposited film were 20 and 60 s. Rinse effectiveness was expressed as the ratio of the amount of protein residue removed from the pipe surface during rinsing, as compared to the magnitude of the initial protein deposit. The rinse effectiveness varied from 73.1% to 94.9% for the range of the CIP parameters investigated. High velocities of rinse water provided a higher level of rinse effectiveness. Increasing the rinse water temperature from 23 °C to 45 °C improved rinse effectiveness significantly (P < 0.05). This impact was not significant when the water temperature was increased from 45 °C to 67 °C and at higher rinse water velocities. Similarly, longer contact time provided less improvement in rinse effectiveness at higher temperatures and velocities as compared to lower temperatures and velocities. There were no significant differences in rinse effectiveness when comparing reused and unused water (normal tap water) within the range of velocities evaluated.