Physical and Mechanical Properties of Pea Starch Edible Films Containing Beeswax Emulsions

ABSTRACT:  Hydrophobic beeswax emulsions were incorporated into hydrophilic starch films to modify physical, mechanical, and thermal properties of the films. Beeswax was added in the film-forming solution of high-amylose pea starch (35% to 40% amylose w/w) at the level of 0%, 10%, 20%, 30%, and 40% w/w of starch with glycerol as a plasticizer (40/60 of glycerol/starch). Addition of beeswax affected mechanical properties, significantly reducing tensile strength and elongation and increasing elastic modulus. Beeswax addition decreased water vapor permeability and increased oxygen permeability. However, the addition of hydrophobic wax particles in starch films marginally affected these physical properties below 30% beeswax in the films. Beeswax addition at the 40% concentration formed amylose–lipid complex that caused the dramatic changes of physical and thermal properties of the films.     

水解淀粉与乙二醛对棉织物的抗皱整理

采用水解淀粉与乙二醛复配整理剂对棉织物进行抗皱整理,通过正交试验,讨论水解淀粉、乙二醛和催化剂用量、焙烘温度和焙烘时间等因素对整理后棉织物折皱回复角提高率和断裂强力保持率的影响。得出最优整理工艺参数:淀粉质量浓度40 g/L、乙二醛质量浓度7 g/L、催化剂质量浓度40 g/L、焙烘温度140℃、焙烘时间5 min。在此最优工艺条件下,整理后棉织物的折皱回复角提高率为30%~45%,断裂强力保持率为88%~95%。     

高膳食纤维面团热机械学及面包的烘焙特性

研究大豆纤维粉(soybean dietary fibre,SDF)和玉米抗性淀粉(resistant starch,RS)及其混合物以20%、30%比例部分替代小麦粉在高膳食纤维面包中的应用,并分析高膳食纤维对面团热机械学特性及面包烘焙特性的影响。结果表明:SDF与RS的引入可提高面团持水性与吸水率(分别提高43.3%～63.3%和5%～7.6%),降低C5-C4值,对淀粉回生产生一定的抑制作用。两者对面团稳定时间和C1-C2的影响不同,RS会显著降低面团稳定时间(为对照组的53.52%～66.46%),增大C1-C2值24.14%～27.59%,蛋白质弱化度提高,而SDF对此则具有积极作用;通过对面包的烘焙特性分析发现,SDF与RS共用时具有协同作用,生产的面包不仅膳食纤维与蛋白质含量高,质构与风味较单独添加SDF有所改善,且提高了RS单独应用时的面包水分含量,提高得率。综合面包比容、色泽、质构与营养而言,5%SDF-15%RS和10%SDF-10%RS组制作的高膳食纤维面包品质最佳,且口感良好。     

Foams Prepared from Whey Protein Isolate and Egg White Protein: 2. Changes Associated with Angel Food Cake Functionality

ABSTRACT:  The effects of sucrose on the physical properties and thermal stability of foams prepared from 10% (w/v) protein solutions of whey protein isolate (WPI), egg white protein (EWP), and their combinations (WPI/EWP) were investigated in wet foams and angel food cakes. Incorporation of 12.8 (w/v) sucrose increased EWP foam stability (drainage 1/2 life) but had little effect on the stability of WPI and WPI/EWP foams. Increased stability was not due to viscosity alone. Sucrose increased interfacial elasticity ( E  ') of EWP and decreased E' of WPI and WPI/EWP combinations, suggesting that altered interfacial properties increased stability in EWP foams. Although 25% WPI/75% EWP cakes had similar volumes as EWP cakes, cakes containing WPI had larger air cells. Changes during heating showed that EWP foams had network formation starting at 45 °C, which was not observed in WPI and WPI/EWP foams. Moreover, in batters, which are foams with additional sugar and flour, a stable foam network was observed from 25 to 85 °C for batters made from EWP foams. Batters containing WPI or WPI/EWP mixtures showed signs of destabilization starting at 25 °C. These results show that sucrose greatly improved the stability of wet EWP foams and that EWP foams form network structures that remain stable during heating. In contrast, sucrose had minimal effects on stability of WPI and WPI/EWP wet foams, and batters containing these foams showed destabilization prior to heating. Therefore, destabilization processes occurring in the wet foams and during baking account for differences in angel food cake quality.     

Principles and practice of near infra-red (NIR) reflectance analysis

Near infra-red (NIR) analysis is now widely used for the rapid analysis of many agricultural and food products for protein, moisture, oil, starch, sucrose, fibre, grain texture and lysine. Research has shown that the technique can also be used for the prediction of malting quality of barley, baking quality of wheat and measurement of the degree of starch damage in flour.
The technique of NIR analysis uses very small differences in absorption of NIR radiation at wavelengths corresponding to overtones and combinations of fundamental IR frequences of chemical functional groups that are characteristic of particular analytes. Complex regression mathematics is used to transform these absorption measurements into an analytical result.     

Changes in Starch Properties of Corn Tortillas during Storage

Starch properties of corn tortillas were characterized during storage. Tortillas were chopped into pieces, macerated with ethanol, centrifuged, extracted again with ethanol, centrifuged, dried, and ground into flour to dehydrate and stabilize starch. Water absorption and water solubility at 25°C, starch pasting properties, and amount and molecular weight of starch extracted at 95°C in water were quantified. Increased levels of soluble amylopectin and increased cold paste viscosity distinguished fresh (0, 0.5, and 1 h) from aged (120 h) tortillas. Water solubility at 25°C decreased continuously during storage; whereas, water absorption increased 0.5 h after baking and then decreased during storage. Rapid changes in starch properties were stabilized using the dehydration procedure and clearly distinguished by pasting viscosities and other methods. Measured starch properties were consistent with very rapid associations (retrogradation) of amylose and rapid associations of amylose and amylopectin yielding insoluble structures in corn tortillas. Retention of some starch crystal nuclei after baking facilitated starch associations that yielded rapid structural changes in corn tortillas.     

Production and Properties of Spin‐Coated Cassava‐Starch‐Glycerol‐Beeswax Films

Cassava‐starch based polymer films containing glycerol as a plasticizer (1.0‐2.5‐5.0%, w/w) and different lipids as additives (paraffin, stearyl alcohol, and beeswax – 0.25‐0.5‐1.0%, w/w) were produced. Control films were produced by heating a mixture of glycerol, starch, and water, while treated films were produced by the addition of lipids/ ethanol solutions. The solutions were kept at around 70ºC during amalgamation, and once congealed, were placed in a vacuum oven for 1 h at 90ºC. The solutions were then spun on 7‐inch diameter non‐stick disks, allowed to dry, and conditioned at 23ºC and 50% RH before testing. Cassava starch‐glycerol‐beeswax films were successfully produced with a stable film structure at glycerol concentration equal or below 5% (w/w). Addition of glycerol and beeswax did not visually change the color of the films. Increasing glycerol content improved elongation while decreasing tensile strength. Increasing the glycerol concentration from 1.0 to 5.0% increased the water vapor permeability by 150% and addition of beeswax further increased these values by 250%.     

Effects of cellulosic fibre on physical and rheological properties of starch,gluten and wheat flour

In this study, we report on the effects of cellulose fibres of different particle size on changes to dough water absorption and rheology; and on effects of fibre on starch and gluten, separately, at different levels of fibre incorporation (0.1–10%). Water absorption and dough‐mixing properties were affected with fibre incorporation, with 40‐μm fibre incorporation resulting in greater absorption values. Dough stickiness and extensibility were affected by cellulose fibre particle size, and decreased with increasing fibre addition. Flour or starch and fibre mixtures were evaluated using a Micro ViscoAmlyoGraph (MVAG), and the resulting gel firmness was measured using a texture analyzer. MVAG peak and final viscosities of flour samples decreased with increasing fibre content. Starch–fibre interactions followed a similar trend as flour–fibre treatments. Gluten–fibre interactions were also measured using a Gluten Peak Tester on flour–fibre and gluten–fibre mixtures. Cellulose fibre enhanced the kinetics of gluten aggregation.     

The use of normal and heat-treated barley flour and waxy barley starch as anti-staling agents in laboratory and industrial baking processes

Normal and heat-treated barley, both as flour and waxy starch, were added at a concentration of 3% to a white wheat bread. The effect not only of selected additives, but also of laboratory- and industrial baking processes on stalling was evaluated. Laboratory baked breads with heat-treated barley flour differed from control breads with regard to water content, firmness and amylopectin retrogradation. The influence of water content on firmness increased with storage time. All laboratory baked breads with barley additives, except normal barley flour, were less firm after 7 days of storage as compared to the control although amylopectin retrogradation tended to increase. Improved water absorption, and consequently, increased water content and/or different water binding capacities of the flour/starch could explain these results. Industrial baking caused higher water losses, especially in breads containing additives, thus reducing the effects on amylopectin retrogradation and firmness.     

乙二醛/水溶性酯Y在纯棉织物防皱整理中的应用研究

研究了乙二醛/水溶性酯Y无甲醛防皱整理剂对纯棉织物的最佳应用工艺以及防皱整理后纯棉织物的耐水洗牢度。通过对乙二醛与水溶性酯Y的配比、焙烘温度、焙烘时间、催化剂的种类、催化剂的用量对整理效果的影响进行了分析,结果表明,最佳工艺:乙二醛与水溶性酯Y比例4∶3(质量比),整理剂的质量分数7%,催化剂柠檬酸质量浓度5 g/L,焙烘温度160℃,焙烘时间2 min。     

Physical and Functional Properties of Arrowroot Starch Extrudates

ABSTRACT:  Arrowroot starch, a commercially underexploited tuber starch but having potential digestive and medicinal properties, has been subjected to extrusion cooking using a single screw food extruder. Different levels of feed moisture (12%, 14%, and 16%) and extrusion temperatures (140, 150, 160, 170, 180, and 190 °C) were used for extrusion. The physical properties—bulk density, true density, porosity, and expansion ratio; functional properties such as water absorption index, water solubility index, oil absorption index, pasting, rheological, and textural properties; and in vitro enzyme digestibility of the extrudates were determined. The expansion ratio of the extrudates ranged from 3.22 to 6.09. The water absorption index (6.52 to 8.85 g gel/g dry sample), water solubility index (15.92% to 41.31%), and oil absorption index (0.50 to 1.70 g/g) were higher for the extrudates in comparison to native starch (1.81 g gel/g dry sample, 1.16% and 0.60 g/g, respectively). The rheological properties, storage modulus, and loss modulus of the gelatinized powdered extrudates were significantly lower ( P < 0.05) and these behaved like solutions rather than a paste or a gel. Hardness and toughness were more for the samples extruded at higher feed moisture and lower extrusion temperature, whereas snap force and energy were higher at lower feed moisture and temperature. There was a significant decrease in the percentage digestibility of arrowroot starch (30.07% after 30 min of incubation with the enzyme) after extrusion (25.27% to 30.56%). Extrusion cooking of arrowroot starch resulted in products with very good expansion, color, and lower digestibility, which can be exploited for its potential use as a snack food.     

Physical,thermal and structural properties of rice starch as affected by the addition of bamboo shoot shell fibres

The effects of different bamboo shoot shell fibre (BSSF) content (1, 2, 5 and 10%, w/w) on the physical, thermal and structural properties of rice starch were investigated. BSSFs significantly affected the properties of rice starch by competitive water absorption and hydrogen bonding. With increased BSSF content, the breakdown value and pasting temperature of rice starch were increased, whereas the peak viscosity, final viscosity and setback value were decreased. Thermodynamic results showed that the gelatinisation temperature and gelatinisation enthalpy of rice starch were significantly increased by the 5% and 10% BSSFs. Furthermore, BSSFs interconnected with amylose through hydrogen bonds to restrain gel-structure formation, thereby resulting in low storage modulus and loss modulus of rice starch paste. A loose structure of rice starch supplemented with 10% BSSFs was clearly visible, exhibiting the minimum values of hardness (32.12 ± 4.47 g) and adhesiveness (64.70 ± 17.32 g). Moreover, BSSFs increased the amount of short-range ordered structures but had no effect on the crystal type of rice starch. These results may contribute to the manufacture and development of fibre-enriched starchy products.     

Relationship between thermomechanical properties and baking expansion of sour cassava starch (Polvilho azedo)

The factors involved in the baking expansion of native and sour cassava starch doughs were compared with those of native corn starch. Unlike corn starch dough, native and sour cassava starch doughs showed expansion properties during baking. The storage modulus E ′ decreased for cassava starch doughs before baking expansion, but remained unchanged for corn starch dough. Expansion during the baking of sour cassava starch was attributed to water vaporisation and the fluidity of starch paste. The fact that temperature and weight loss variations at adequate water contents were significantly greater for cassava than corn starch dough is indicative of the important role played by starch melting in expansion. Expansion ability could be correlated with changes in dough–crumb thermomechanical properties when close to the starch melting temperature. © 2001 Society of Chemical Industry     

Effect of structural characteristics of modified waxy corn starches on rheological properties,film‐forming solutions,and on water vapor permeability,solubility, and opacity of films

Waxy corn starch (amylopectin) and three of its chemical derivatives: acetylated cross‐linked (ACLS), oxidized (OS), and octenyl‐succinylated (OSA), were used together with additives such as Tween 80, sorbitol, and beeswax suspension or safflower oil to test their effect on film‐forming solutions (FFS) and films. The objectives of this study were the starch structure characterization, and its correlation with rheological properties of FFS and solubility, opacity, and water vapor permeability (WVP) of the produced films. Analysis of starch structure, rheological characterization, and films micrographs revealed that the starches contained predominantly low MW amylopectin molecules and film properties depended on their ability to reorganize. Additionally, the interaction among groups introduced in modified starches or with additive molecules can hinder or promote starch reorganization, resulting in films with increased or reduced WVP, solubility and transparency properties. Films were obtained by casting and showed a thickness less than 41 µm. Films prepared with OS and beeswax exhibited the best reorganizing capacity of FFS, resulting in less soluble (30.0 ± 1.6%), highly transparent (23.2 ± 3.3 UA × nm) and less permeable films (0.485 ± 0.016 g · mm · m⁻² · h⁻¹ · kPa⁻¹). On the other hand, ACLS showed an opposite trend which was attributed to a more open film structure. These results contribute to understand the molecular interactions of waxy starch molecules in FFS which may be useful to design tailored coatings.     

Effect of green plantain flour addition to gluten‐free bread on functional bread properties and resistant starch content

Green plantain flour (GPF) was used as a functional ingredient to produce gluten‐free (GF) bread based on a flour blend of rice flour and GF wheat starch (50:50) to improve their functional properties and to increase their resistant starch (RS) content. In pretrials, an addition of up to 30% GPF provided acceptable bread quality with maximum RS content. Based on these trials, two 2³ factorial screening experimental designs were applied, where water content, baking temperature and baking time of GF bread containing 30% GPF addition were optimised. The best baking conditions to achieve satisfying GF bread quality – higher loaf volume, softer crumb firmness and regular porosity structure at the highest RS content could be defined to a maximum addition of water at 160%, baking temperature of 180 °C and baking time of 90 min. The incorporation of GPF showed good potential to improve the quality of GF bread.     

Optimization of microwave baking of model layer cakes

 Response surface methodology was used to optimize the formulation of microwave-baked cakes. The independent variables were water content, emulsifier content baking time, oven power, shortening content and starch type. The quality factors evaluated were specific gravity of batter and volume index, uniformity index and tenderness of the crumb. Constraints for quality factors were obtained by conventional baking of American Association of Cereal Chemists high-ratio cake formulation. Multiple contour plots showed the optimum region for various water and shortening combinations at different emulsifier, time and power levels. Cakes formulated with wheat starch, containing 0.3% polysorbate 60, 133.7% water and 45.2% shortening (flour substitute basis), baked for 6 min at 100% power yielded acceptable cakes that can compete with conventionally baked cakes. Rice and corn cakes had lower quality than conventionally baked high-ratio cakes. Power was found to be the most efficient independent variable affecting all the dependent variables. Received: 26 August 1999 / Revised version: 11 October 1999     

Physical properties and chemical forces of extruded corn starch fortified with soy protein isolate

The effect of soy protein addition on physical properties of extruded corn starch was studied. The correlations between the chemical bonds in proteins and the physical properties of extrudates were analysed. Increasing soy protein isolate content resulted in higher expansion ratio (ER) but lower bulk density (BD), hardness, water solubility index (WSI), degree of starch gelatinisation (DSG), content of sulphydryl (SH) groups and protein solubility in phosphate buffer. In the other hand, increasing the processing temperature resulted in higher ER, water absorption index, DSG, contents of the SH group and disulphide (SS) bond but in lower specific mechanical energy, BD, hardness and WSI. The results indicated that changes in the chemical bonds in proteins had a significant effect on the apparent physical properties of extrudates. More protein–protein and protein–starch cross‐linking reactions occurred through new chemical linkages, such as the nondisulphide covalent bonds and hydrogen bonds, which are beneficial to the expansion of starch‐based products.     

Physicochemical characterisation and in vitro Starch digestion of Avocado Seed Flour (Persea americana V. Hass) and its starch and fibrous fractions

The avocado seed is considered a by-product of their pulp exploitation and today it does not present relevant food or industrial applications. In this study, we evaluate the potential use of its flour, their isolated starch and fibre fractions. After processing, the flour yielded 46.28%, and showed 6.7% of protein and low fat and ash contents (3.4, and 2.71% respectively). The starch yielded 27.28% with low-fibre content that influenced its viscosity properties; as well as their water absorption index (WAI), water solubility index (WSI) and oil absorption index (OAI), that were 2.43%, 11.22% and 0.16% respectively. The in vitro starch digestion of the different obtained fractions showed higher amounts of rapidly digestible starch (56.8%–75.36%, flour and starch respectively). The functional properties of the materials were correlated with strong molecular interactions with their apparently unique amylose structure; for this, this by-product may have different potential for food applications.     

Effect of native and acetylated‐crosslinked waxy corn starch‐beeswax coatings on quality attributes of raspberries during storage

Edible coatings (ECs) are a thin layer of a mixture of edible materials, applied in the liquid state and dried over the surface of a food product to maintain its quality during storage. This work was aimed to study the effect of ECs made from wx corn starch (WCS) or acetylated cross‐linked starch (ACLS) added with beeswax on fresh raspberry quality attributes during short‐term cold storage. Freshly harvested fruits were coated, dried, packed in plastic trays and stored up to 8 days at 4°C. During storage quality parameters such as firmness, respiration rate, anthocyanins content, total phenols, color changes, and weight loss were evaluated. A clear effect on control of respiration rate was observed in coated raspberries. Respiration rate of uncoated fruit was 4.5 ± 0.28 mmol/kg/h and decreased to 4.2 ± 0.27 for ACLS and to 4.1 ± 0.08 mmol/kg/h for WCS‐coated raspberries, after 56 h of storage at 15°C. Ethylene production followed a similar trend under these conditions decreasing from 0.043 ± 0.005 to 0.034 ± 0.004 mmol/kg/h for uncoated and ACLS coated fruits, respectively, indicating an effect on ripening control. Additionally, ACLS and WCS coatings permitted the preservation of color without affecting anthocyanins content. However, the presence of anaerobic metabolites and reduction of terpenes production in cold stored coated raspberries indicated hypoxic conditions, which can adversely affect shelf‐life quality attributes of raspberries such as firmness and weight loss.