Starch-based Matrix Research Articles

Including protein hydrolysates during thermal processing mitigates the starch digestion of resulted starch-based binary matrix

Staple foods with starch and protein components are usually consumed after thermal processing. To date, how including protein hydrolysates (with varied hydrolysis degrees) tailors the structure and digestion features of starch-based matrix with thermal processing has not yet been sufficiently understood. Here, corn starch (CS), soy protein isolate (SPI), and soy protein isolate hydrolysates (SPIH) with different hydrolysis time (5–60 min) were used to prepare starch-based binary matrices. With the addition of SPI or SPIH during thermal processing, the resultant binary systems exhibited higher thermal stability (breakdown visibility was increased by 1.9–10.8 times), denser networks, and fewer short-range orders (R995/1022 was decreased by up to 15.3 %). These structural changes allowed an inhibited starch digestion within the binary system, especially with increased SPI or SPIH content. Compared with CS, the content of resistant starch (RS) for CS-SPI binary complex (10:3 w/w) increased from 9.89 % to 16.69 %. Compared to SPI, SPIH inclusion displayed a stronger inhibitory effect on starch digestion since the reduced molecule size of SPIH probably enhanced its interplays with starch or amylase. For instance, the 10:3 w/w starch-SPIH 60 binary matrix possessed the highest RS content (19.07 %).

Enrichment of resistant starch in starch-protein hydrolysate binary matrix by modulating pH during thermal processing

Controlling the digestion features of starch-based food matrices following thermal processing plays vital roles in reducing risks of metabolic diseases such as obesity and type II diabetes. To date, it remains largely unclear how regulating the pH during thermal processing alters the microstructure and digestion features of starch-based matrix including protein hydrolysates. Considering this, corn starch (CS) and soybean protein isolate (SPI) (or its hydrolysates (SPIH)) were used to prepare thermally-processed CS-SPI and CS-SPIH binary matrices under different pH values (3 to 9), followed by inspection of changes in the structures and digestibility using combined methods. It was found that including SPI (especially SPIH) caused structural changes of those binary systems, such as reduced network sizes, increased V-crystals and reduced nanoscale structures, which could allow more resistant starch (RS). This phenomenon was especially true when including SPIH with regulated pH value. For instance, SPIH inclusion at pH 5 caused the highest RS content (about 20.30%), presumably linked to the reduced molecule size of SPIH with strengthened aggregation at pH 5. In contrast, the acidic (pH 3) and alkaline (pH 9) conditions allowed reduced short-range orders and tailored porous networks and thus less RS (ca. 17.46% at pH 3 and 16.74% at pH 9).

Fabricating a visibly colorimetric film via self-releasing of anthocyanins from distributed mulberry pomace particles in hydrophilic sodium carboxymethyl starch-based matrix to monitor meat freshness

A highly distinguishable indicator film was developed based on sodium carboxymethyl starch, κ-carrageenan, carboxylated cellulose nanocrystals and mulberry pomace particles (MPPs). As the content of MPPs increased from 0 % to 6 %, the tensile strength decreased from 11.71 MPa to 5.20 MPa, the elongation at break increased from 26.84 % to 43.76 %, respectively, and the haze increased from 34.12 % to 52.10 %. The films accurately exhibit a color change from purple to blue-green under alkaline conditions. The enhanced haze improved the visible resolution of the films during the color-changing process. The films with the size of 7.50 mm × 7.50 mm and 10.0 mm × 10.0 mm exhibited obvious color changes when the total volatile basic nitrogen reached 14.60 mg/100 g and 19.04 mg/100 g, respectively, which accurately indicated the quality of pork and fish. This study will offer a simplified path to improve both accurate sensitivity and distinguishability for smart films.

The role of various plastisizers and fillers additions in improving tensile strength of starch-based bioplastics: A mini review

The general public uses plastic extensively, particularly in food packaging. Plastic raw materials are generally petroleum derivatives with advantages such as high tensile strength, low cost, lightweight, ease of manufacture, and application. However, there are other disadvantages to plastic, which is not easily biodegradable. As a result, researchers have expressed a strong desire to develop biodegradable plastics in order to reduce the accumulation of non-biodegradable plastics in the environment. One of the candidates for producing bioplastic using natural resources is biodegradable plastics. Bioplastics based on starch are a common material used in the production of bioplastics. However, because bioplastics have lower tensile properties than conventional plastics, fillers are used to increase the strength of bioplastics. Fillers are used to reduce plastic cost, shrinkage during the setting process, and to improve tensile strength and hardness. As a result, the tensile and morphology of several starch-based biodegradable plastics with chitosan, CMC fiber, and clay as fillers will be reported in this review. According to our mini-review, sorbitol and CMC are very good plasticizers for starch-based bioplastics, and CMC has a higher crystallinity form, promoting greater interaction between the cellulose chains and starch-based matrix.

Charged-cellulose nanofibrils as a nutrient carrier in biodegradable polymers for enhanced efficiency fertilizers

An enhanced efficiency fertilizer (EEF) is essential for sustainable agriculture, and here, we evaluated cellulose nanofibrils (CNF) as a nutrient carrier dispersed in biodegradable polymeric matrices. CNF were functionalized with negative (CNF−) and positive (CNF+) charges to improve (i) the CNF-nutrient and (ii) the CNF-polymeric matrix interactions. The CNF encapsulated the KNO3 nutrient by spray drying (microcapsules) and then inserted into a poly (hydroxybutyrate)/starch-based matrix by melt-compounding (tablets). These materials were morphologically, structurally, and thermally characterized before and after biodegradation. Nutrient release profiles showed the microcapsules released the nutrients for up to 1 h, while the tablets did for 8 h in water and over 80 days in soil. Tablets with CNF− released NO3− faster than K+, and those with CNF+ behaved inversely. Besides, the biodegradation efficiencies were up to 75 % in 120 days. The CNF charges affected nutrient release and the matrix biodegradation, ensuring the matrices were harmless to the environment.

A material proposed for re-use of hemp shives as a waste from fiber production

This work proposes a material obtained from hemp shives mixed with another industrial waste, clay from pottery, in a self-produced starch-based matrix. The preliminary results, obtained through Charpy impact, Shore D hardness and flexural tests, suggest that, despite both the ceramic and the ligneous fillers are effective to a point, the consolidation of the material needs improvement. This is confirmed by the significant presence of internal porosities, which coalesce during fracture. In particular, it would be necessary to reduce the dimension of hemp shives until obtaining a more regular fibrous geometry and applying a more uniform pressure on the whole section of the material.

Effect of Carnauba Wax and Coconut Fiber Contents on Tensile Properties of Corn Starch-Based Biocomposites

This work aims investigate the changes on tensile properties of biocomposites obtained by addition of carnauba wax and coconut fibers in a corn starch matrix. The influence of carnauba wax and coconut fibers contents on tensile strength, modulus of elasticity and elongation at break was studied using a response surface methodology. A central composite design based on three levels of carnauba wax content (0, 10 and 20 %) and coconut fibers content (0, 10 and 20 %) was elaborated. Empirical models were obtained to describe these properties as function of coconut fiber and carnauba wax contents. Optical microscopy was carried out to visualize the dispersion and interactions between coconut fibers, carnauba wax and starch matrix in the biocomposites. In presence of carnauba wax, the biocomposite became more compact and with a better interaction between the corn starch-based matrix and coconut fibers reinforcement. It was observed that tensile strength and modulus of elasticity rise with the increase in carnauba wax and coconut fiber contents. Moreover, the elongation at break increases with the addition of coconut fiber, while a decrease in the values of this property occurs with the addition of carnauba wax.

Properties of Thermoplastic Corn Starch Based Green Composites Reinforced with Barley (Hordeum vulgare L.) Straw Particles Obtained by Thermal Compression

Currently, greater environmental awareness promotes research and development advances in biodegradable materials; they represent an alternative that decreases the environmental impact caused by traditional synthetic plastics. This study consists of the development and characterization of thermoplastic corn starch-based composites, reinforced with barley straw particles made by thermal compression. The study materials were prepared by using three particle concentrations (5, 10, and 15 %), while the matrix (0 %) was used as a reference. A mechanical evaluation of all samples was carried out, as well as that of their water absorption properties. They were also characterized by scanning electron microscopy (SEM), infrared spectroscopy (FTIR), X-ray diffraction (XRD), and flammability tests. The inclusion of straw in the thermoplastic matrix increased water absorption and quickened carbon formation, although it also increased its tensile strength (7 MPa) and the Young’s modulus of activity (MOE) (420 MPa) with a 15 % reinforcement. The FTIR analysis highlights the presence of a carbonyl signal (1720 cm-1) caused by a thermal breakdown (caramelization) linked to barley particles. Moreover, X-ray diffraction demonstrated a VA-type crystallinity pattern (anhydrous) within the biocomposites and an increase of the crystallinity index, through incorporating barley particles in the thermoplastic corn starch-based matrix.

Multiple Reprocessing Cycles of Corn Starch-Based Biocomposites Reinforced with Curauá Fiber

Biocomposites with a corn starch-based biodegradable polymer as matrix and 10 wt% vegetable curaua fiber were processed by injection molding and were submitted to reprocessing up to ten cycles with or without 3 wt% of maleic anhydride grafted polypropylene as coupling agent. The effect of reprocessing on hardness, impact and tensile properties as well as on the morphology, thermal properties, chemical structure and soil degradation behaviour of the matrix and biocomposites was evaluated. Curaua fibers have increased hardness, impact and tensile strengths as well as increased tensile modulus and decreased elongation at break of the biocomposites with respect to starch-based matrix and these properties slightly decreased or no considerable changes were observed with the reprocessing cycle increase. The addition of coupling agent promoted an increase in all properties and they remained almost constant with the reprocessing cycle increase. Thus, the incorporation of curaua fiber within starch-based matrix can improve the mechanical properties of the biocomposites which showed potential to be recycled despite the weight loss in soil degradation tests reached around 10 wt% after 230 days for biocomposites reprocessed ten cycles.

Starch-Based Biopolymer Reinforced with High Yield Fibers from Sugarcane Bagasse as a Technical and Environmentally Friendly Alternative to High Density Polyethylene

Greener composites, as alternatives to more common materials, should also achieve technical and economic feasibility to be commercially competitive. This study presents the results obtained from using a biodegradable starch-based matrix, and a natural fiber reinforcement coming from sugarcane bagasse, currently an agro-waste. The sugarcane bagasse biomass was treated to obtain four kinds of fibers with different morphological and chemical properties. The fibers were used to obtain composite materials, which were then tested for tensile properties. The results showed that some of the composites were suitable to replace high density polyethylene, from a technical and environmental point of view. The comparatively higher cost of the biobased matrices hinders the substitution, but the higher the fiber content, the lower the economic disadvantage. A micromechanical test and a sensitivity analysis showed that the fiber orientation had the highest impact on the tensile strength, followed by the fibers mean length and the quality of the interphase between the fibers and the matrix

Influence of Sucrose Content on Expansion of Extruded, Starch-Based Pellets during Microwave Vacuum Processing

The influence of sucrose content on microwave-induced expansion of starch-based, extruded pellets under vacuum was investigated. Expansion of extruded pellets with different sucrose contents (0, 10 and 20%) was investigated in a microwave vacuum-drying system. With increasing sucrose content, volume expansion showed a nearly linear increase. Also, the number of pores increased with increasing sucrose content. A softening of the matrix might facilitate nucleation. Pore areas decrease with increasing number of pores. We therefore assume that nucleation has the strongest impact on pore area distribution. Mainly pillow-shaped and round final products were found. The shape of the final products could be related to the glass transition temperature Tg of the intermediate products and to heating and drying characteristics of the pellets during microwave vacuum processing. Tg decreases with increasing sucrose contents. If expansion of the initially cylindrical pellets takes place within the rubbery state, round final products are formed. If a glassy outer layer is built due to evaporation cooling of the surface and high Tg of the matrix, the pellets rupture upon expansion and the pillow shape forms. Practical Applications In contrast to direct expanded extruded snacks, third-generation snacks are generally produced by pre-drying nonexpanded, extruded pellets, followed by a separated expansion process. By this process route, extrusion can be performed at high moisture contents, moderate temperatures and moderate shearing conditions. This is beneficial in terms of preserving thermal- and mechanical-sensitive ingredients. A special feature of the process investigated in this study is that the expansion is achieved by microwave vacuum processing that allows an indirect expansion without a time- and energy-consuming pre-drying process. This study shows that total volume and inner structure of the expanded pellets is strongly influenced by the amount of sucrose added to the starch-based matrix. With these information producers can turn structure-related properties such as appearance, crispiness and crunchiness to target values.

Processing and Characterization of Nano-biocomposites Based on Mater-Bi® with Layered Silicates

The development of new nano-biocomposites has been one of the main research areas of interest in polymer science in recent years, since they can combine the intrinsic biodegradable nature of matrices with the ability to modify their properties by the addition of selected nano-reinforcements. In this work, the addition of mineral nanoclays (montmorillonites and sepiolites) to a commercial starch-based matrix is proposed. A complete study on their processing by melt-intercalation techniques and further evaluation of the main properties of nano-biocomposites has been carried out. The results reported show an important infl uence of the nano-biocomposites morphology on their fi nal properties. In particular, the rheological and viscoelastic characteristics of these systems are very sensitive to the dispersion level of the nanofi ller, but it is possible to assess that the material processing behaviour is not compromised by the presence of these nano-reinforcements. In general, both nanofi llers had a positive infl uence in the materials fi nal properties. Mechanical performance shows improvements in terms of elastic modulus, without important limitations in terms of ductility. Thermal properties are improved in terms of residual mass after degradation and low improvements are also observed in terms of oxygen barrier properties. ® , nanoclays, melt intercalation, characterisation

Effect of Microstructure on the Tensile and Fracture Properties of Sisal Fiber/Starch-based Composites

In this study, the effect of microstructure on the tensile and fracture properties of injection molded biocomposites consisting of starch-based matrix and short sisal fibers has been investigated. Tensile tests are carried out on samples cut in longitudinal (L) and transverse (T) directions with respect to the melt flow direction. An increasing trend in Young’s modulus and tensile strength with fiber content is found, irrespective of the sample orientation. In addition, this reinforcing effect is more pronounced for L samples with many fibers mainly oriented longitudinally to the loading direction. Quasistatic fracture tests are also performed on SENB specimens with cracks propagating both parallel and perpendicular to the melt flow direction. The stress intensity factor is found to increase with fiber content, and it also depends on fiber orientation. The observed trend in fracture toughness with fiber content and microstructure is explained in terms of the fiber pullout mechanism. Puncture tests are carried out for all compositions. Injection molded composites exhibit higher values of total fracture energy than neat matrix. Furthermore, fiber orientation induces different patterns in the damage zone. Finally, several theoretical models are used in this study to predict the elastic properties of these composites.