Thermoplastic starch/whey protein isolate/rosemary essential oil nanocomposites obtained by extrusion process: Antioxidant polymers

Active substances are added to polymers to act as a barrier to external elements, protecting the product. This article evaluated the effect of the addition of sodium montmorillonite (MMT) nanoparticles and the antioxidant activity of rosemary essential oil (EO) in thermoplastic starch/whey protein isolate (TPS/WPI) nanocomposites obtained by extrusion. X-ray diffractograms showed dispersion/exfoliation of the MMT in the TPS/WPI matrix. The nanocomposites presented rough surface with the presence of porosity as shown by scanning electron microscopy images. Thermogravimetric analysis revealed that the combination between MMT and rosemary EO increased thermal stability of nanocomposites. The addition of rosemary EO became the films less rigid, weaker and had an antioxidant effect as shown by mechanical properties and 2,2-diphenyl-1-picrylhydrazyl assay. The optical properties showed in opaque greenish yellow nanocomposites. Therefore, the addition of rosemary EO in nanocomposites showed an alternative for use as antioxidant polymers in packaging material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47619.     

Morphology and enzymatic degradation of thermoplastic starch–polycaprolactone blends

This study's aim was to evaluate the effect of processing conditions on the morphology and enzymatic degradation of 50/50 (w/w) thermoplastic starch–polycaprolactone blends. The blends, produced from native potato starch, glycerol, and polycaprolactone in a melt mixer using different mixing speeds and temperatures, were cocontinuous, and the blends were very homogeneous. Enzymatic hydrolysis was performed using Bacillus licheniformis alpha‐amylase and Aspergillus niger glucoamylase on both milled and intact samples. The thin layer of polycaprolactone (≈ 5 μm) formed on the surface of the thermoplastic starch–polycaprolactone blends during compression molding strongly reduced the rate of enzymatic hydrolysis. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2594–2604, 1999     

Antioxidant and physicochemical properties of blended films based on gelatin‐sodium caseinate activated with natural extracts

Blend films of pigskin gelatin (GEL) and sodium caseinate (SCas) with boldo (B), guarana (G), cinnamon (C), or rosemary (R) extracts added were studied. SCas and extracts addition in blend films significantly increased the gloss and better UV barrier of GEL100 films. Extracts incorporation significantly decreased the rigidity and elongation of GEL100 films, which were significantly improved in GEL75:SCas25 blend films with extracts (EM = 295.69 ± 21.75 MPa and EB = 11.60 ± 3.43%). SCas addition not affected the TS parameter. The water vapor permeability of GEL100 films was reduced in blended films with extracts, showing the lowest value for GEL75:SCas25 + R (0.99 ± 0.07 × 10¹⁰ g s^?1 m^?1 Pa^?1). FTIR and microstructure analyses showed good compatibility for all components. The antioxidant activity of GEL100 was significantly increased with SCas and extracts addition (GEL50:SCas50 + R = 4.31 ± 0.11 mM ), suggesting the application of these films as an active food packaging material. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44467.     

Influence of natural antioxidants on the formation of trans‐fatty‐acid isomers during heat treatment of sunflower oil

The intake of foods containing trans fatty acids (TFAs) can have deleterious effects on human health, mainly on the cardiovascular system. Thus, it is important to consider the processes that form TFAs in foods, and the alternatives to minimise their formation. The influence of two added natural antioxidants on TFA formation during heat treatment (120 h at 180°C) of sunflower vegetable oil were examined: rosemary extract (Rosmarinus officinalis L.) (1 g per kg oil) and lutein (0.1 g per kg oil). Changes in FA composition were determined using Ag‐ion SPE and gas–liquid chromatography, with total polar compounds determined using dielectric constant measurements and the index of atherogenicity was calculated. Total TFAs with ≥1 trans double bond increased from 0.91 to 1.71% in control samples; this increase was significantly less with both rosemary extract (1.55%) and lutein (1.43%) additions. Among the individual TFAs, significant increases were seen for C18:1,t‐9, C18:2,t‐9,t‐12 and C18:2,c‐9,t‐12/9‐t,12‐c. Polar compounds also increased, with the highest concentrations in control samples, and significantly less with both rosemary extract and lutein additions. According to results of our study, we can summarize that addition of lutein have greater effect on reduction of TFA formation than rosemary extract. Practical applications: Antioxidants, particularly from plants, are widely used in the food industry. They can provide benefits in food preparation, including improving colour, odour and stability, acting as acid regulators and natural preservatives. They have also become accepted by customers and consumers, and so indirectly they have had effects on consumer perception. Addition of natural antioxidants such as rosemary extract is usually limited by the sensory characteristics of the food, with one study showing that addition of rosemary extract at 1–3 g per kg vegetable oil is recommended. The effects of antioxidants on the formation of TFAs in vegetable oils has not been well studied in the literature. Among the already known benefits, the use of such antioxidants as functional ingredients in lipid technologies might reduce the formation of TFAs during thermal treatment.     

A new biodegradable plastic made from starch graft poly(methyl acrylate) copolymer

A starch graft poly(methyl acrylate) copolymer was developed having grafted side chains with molecular weight of less than 500,000. This material can be easily extruded into a film which shows excellent initial tensile strength and elongation. Tensile strength, however, falls off rapidly after 70 hr of water immersion at 25°C. Starch graft poly(methyl acrylate) films show excellent susceptibility to fungal growth, some samples losing more than 40% of their weight after 22 days of incubation with Aspergillus niger. Tensile tests and scanning electron micrographs of the incubated samples, after being freed of mycelium, indicate substantial biodegradation of the starch portion of the copolymer. This material may have application as a biodegradable plastic mulch.     

Biodegradation of blends of polyethylene‐octene elastomer with starches by fungi

Five fungi including Aspergillus niger, Penicilium pinophilum, Chaetoomium globsum, Gliocladium virens and Aureobasium pullulans were used to investigate the biodegradation of starch‐based elastomers: polyethylene‐octene elastomer (POE)/starch and grafted POE‐g‐MAH/starch copolymer blends. The viability of the composite spore suspensions were measured before estimating the fungal growth on the surface of specimens. The weight loss, morphology and mechanical properties of the blended specimens were measured using scanning electron microscopy and a mechanical properties tester after 28 days of culturing. The spore suspension in the experiment showed good viability. Pure POE and POE‐g‐MAH did not allow significant fungal growth. Pure POE did not lose weight or have a change in tensile strength, but pure POE‐g‐MAH lost about 0.07% of its weight with a slight reduction in tensile strength during culture period. There was heavy growth on the surface of POE/starch and POE‐g‐MAH/starch blends after 28 days of culturing. The weight loss of POE/starch and POE‐g‐MAH/starch blends increased with increasing starch content. POE‐g‐MAH/starch blends tended to lose more weight than POE/starch blends. After biodegradation, the surface of POE/starch and POE‐g‐MAH/starch blends became rough with many holes and cracks, indicating that the films were eroded by the fungi. Tensile strength of POE/starch and POE‐g‐MAH/starch blends decreased after culturing because of microbial attack. On the contrary, elongation at break of POE‐g‐MAH/starch blends increased after biodegradation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114:3574–3584, 2009     

Synthesis and characterization of butyl acrylate graft sodium salt of partially carboxymethylated starch

Graft copolymers were synthesized by graft copolymerization of butyl acrylate (BA) onto sodium salt of partially carboxymethylated starch (Na‐PCMS). Ceric ammonium nitrate (CAN), a redox initiator, was used for initiation of graft copolymerization reaction. All the experiments were run with Na‐PCMS having degree of substitution, DS = 0.35. The grafting reaction was characterized by parameters such as % total conversion (%Ct), % grafting (%G), % grafting efficiency (%GE), and % add‐on. Graft copolymers were characterized by infrared spectral analysis and scanning electron microscopy. Variables affecting graft copolymerization reaction such as nitric acid concentration, reaction time, reaction temperature, and ceric ion concentration were investigated. The results revealed that 0.3M CAN as initiator, 0.3M HNO₃, with reaction time 4–4.5 h at 25–30°C were found as suitable parameters for maximum yield of graft copolymerization reaction. © 2006 Wiley Periodicals, Inc. JAppl Polym Sci 102: 3334–3340, 2006     

Synthesis and absorbency of a superabsorbent from sodium starch sulfate‐g‐polyacrylonitrile

A sodium starch sulfate–based superabsorbent was synthesized to improve water and saline absorbencies. A sodium starch sulfate with high degree of substitution was synthesized by the reaction of starch gelatinized with dimethyl acetamide (DMAc)/lithium chloride (LiCl) and a dimethyl formamide–sulfur trioxide (DMF–SO₃) complex. The sodium starch sulfate was then graft‐polymerized with acrylonitrile and the nitrile groups of the sodium starch sulfate‐g‐polyacrylonitrile were converted to a mixture of hydrophilic carboxamide and carboxylate groups by alkaline hydrolysis. The hydrolyzed sodium starch sulfate‐g‐polyacrylonitrile copolymer exhibited improved water and saline absorbencies compared with that of existing starch‐based superabsorbents, resulting from the presence of sulfate groups. The maximum water and saline absorbencies of the sodium starch sulfate–based superabsorbent were 1510 and 126.4 g/g, respectively. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1423–1430, 2001     

Biodegradation of starch and acrylic‐grafted starch by Aspergillus niger

The biodegradation of starch and grafted starch by Aspergillus niger was examined. The grafted polymers were poly(methyl methacrylate) (PMMA) and poly(butyl acrylate) (PBA). Thermogravimetric analysis, Fourier transform infrared, and scanning electron microscopy were used to determine the morphology and degradation degree of each material. The temperature of maximum decomposition for starch decreased as enzymatic degradation proceeded, and it was completed on the 8th day of culturing in a liquid medium. Grafted samples with PMMA and PBA achieved degradation of their starch moiety. PBA in starch‐g‐PBA samples hindered the accessibility of the enzymes to the degradable material, and this resulted in a longer degradation time. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2764–2770, 2003     

Photobiodegradation of low‐density polyethylene/banana starch films

The effects of the starch content, photosensitizer content, and compatibilizer on the photobiodegradability of low‐density polyethylene (LDPE) and banana starch polymer blend films were investigated. The compatibilizer and photosensitizer used in the films were PE‐graft‐maleic anhydride (PE‐g‐MA) and benzophenone, respectively. Dried banana starch at 0–20% (w/w) of LDPE, benzophenone at 0–1% (w/w) of LDPE, and PE‐g‐MA at 10% (w/w) of banana starch were added to LDPE. The photodegradation of the blend films was performed with outdoor exposure. The progress of the photodegradation was followed by determining the carbonyl index derived from Fourier transform IR measurements and the changes in tensile properties. Biodegradation of the blend films was investigated by a soil burial test. The biodegradation process was followed by measuring the changes in the physical appearance, weight loss, and tensile properties of the films. The results showed that both photo‐ and biodegradation rates increased with increasing amounts of banana starch, whereas the tensile properties of the films decreased. The blends with higher amounts of benzophenone showed higher rates of photodegradation, although their biodegradation rates were reduced with an increase in benzophenone content. The addition of PE‐g‐MA into polymer blends led to an increase in the tensile properties whereas the photobiodegradation was slightly decreased compared to the films without PE‐g‐MA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2725–2736, 2006     

Effect of solid-state fermentation on select antinutrients and protein digestibility of cold-pressed and hexane-extracted canola meals

In this study, the effects of solid-state fermentation (SSF), including strain (Aspergillus niger NRRL 334 and A. oryzae NRRL 5590) and fermentation time (24, 48, and 72 h) on the nutritional value of cold-pressed (CP) and hexane-extracted (HE) canola meals were examined. SSF increased the protein content of both types of meals (from ~36% to ~40%) while reducing the oil content of CP meals (from ~12% to 9%). There was a significant reduction (~80%) in the phytic acid content of both types of meals after fermentation using either fungi. Overall, fermented samples showed a decrease in the total phenolic content from 2.7–3.1 to ~1.0 mg gallic acid equivalents (GAE)/g dry meal (DM) (a ~65% reduction), of which specifically the HE meal fermented with A. niger sample had the greatest decrease from 3.1 to 0.6 mg GAE/g DM (~81% reduction). Seventy-two hours of fermentation decreased the in vitro protein digestibility (IVPD) of A. oryzae fermented meals. In contrast, a shorter fermentation time (24 h) increased the IVPD for most samples as compared to the controls (from ~72%–73% to 77%–81%), with the exception of the CP meal fermented with A. niger which had similar IVPD at all fermentation times. Overall, the changes indicate that SSF using A. niger or A. oryzae can be useful to positively modify the composition of different canola meals and improve their nutritional value by significantly increasing the protein content, decreasing the levels of antinutrients, while only slightly reducing IVPD.     

Compatibilization of starch/poly(butylene adipate‐co‐terephthalate) blown films using itaconic acid and sodium hypophosphite

Itaconic acid (IA) has potential as a compatibilizing agent in polymeric blends due to its unique chemical characteristics. Sodium hypophosphite (SHP) has been studied as a catalyst in esterifying reactions using multicarboxylic acids. Starch/poly(butylene adipate‐co‐terephthalate) blown films containing IA, with and without SHP, were produced. The film containing IA presented higher tensile strength (8.166 MPa) and elongation (891.473%) than the control film (5.548 MPa and 487.637%, respectively). When SHP was added (sample IA‐SHP), tensile strength increased even more (9.215 MPa); however, elongation (636.821%) was lower than in the IA film. This behavior was attributed to crosslinking between two starch itaconoate molecules intermediated by SHP. The increase in the compatibility between the polymeric phases justified the lower permeability to water vapor of the IA‐SHP films and was responsible for the production of films with a more compact and homogeneous structure. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46629.     

Bi-layer gelatin active films with “Pitanga” leaf hydroethanolic extract and/or natamycin in the second layer

Research on biopolymers-based active films produced with natural antioxidants and/or antimicrobials has gained attention over the last few years; however, anti-mold activity has been less studied than those of anti-bacteria. The aim of this work was the development and characterization of bi-layer films based on gelatin with natamycin and/or “Pitanga” leaf hydroethanolic extract in the second thin layer in order to determine the effects of these bioactive compounds on bi-layered film properties. The films were characterized regarding their moisture content and solubility in water, optical properties, microstructure, mechanical and thermal properties, water contact angle, water vapor permeability, UV/visible light transmission, X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and antioxidant and anti-mold activities. Active films presented activity against Penicillium spp and Aspergillus niger and demonstrated antioxidant activity, as measured by ABTS ^•+ and DPPH ^• methods. Neither additive used in the films' second layer significantly affected the films' moisture content, thermal properties or the molecular interactions of the polymer matrix, assessed by FTIR, although some mechanical properties were affected, and the water contact angle. In conclusion, bi-layer films have reduced the quantity of additives required to maintain the antioxidant and anti-mold activities, as compared to similar monolayer films of the same thickness.     

Extruded foams prepared from high amylose starch with sodium stearate to form amylose inclusion complexes*

Extruded starch foams were prepared from high amylose corn starch with and without sodium stearate and poly(vinyl alcohol) (PVOH) to determine how the formation of amylose–sodium stearate inclusion complexes and PVOH addition would affect foam properties. X‐ray diffraction and Differential Scanning Calorimetry (DSC) showed that amylose–sodium stearate inclusion complexes were formed by low temperature extrusion and did not dissociate during foam formation by a second extrusion at higher temperatures. In the absence of PVOH, water absorption, and foam shrinkage at 95% RH were decreased because of the hydrophobicity of the complex. PVOH addition increased both the expansion ratio and the shrinkage of the foam, although shrinkage at 95% RH was still less than that observed with uncomplexed amylose. The structural integrity and some tensile properties of stearate‐containing foams were improved by PVOH addition. These results provide the manufacturer of biodegradable starch foams with an inexpensive method for tailoring foam properties for specific end‐use applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43251.     

Use optimization of natural antioxidants in refined, bleached, and deodorized palm olein during repeated deep-fat frying using response surface methodology

An optimization study on the use of oleoresin rosemary extract, sage extract, and citric acid added into refined, bleached, and deodorized (RBD) palm olein in deep-fat frying of potato chips was carried out using response surface methodology (RSM). Results showed that oleoresin rosemary extract was the most important factor affecting the sensory acceptability of potato chips. For taste and odor, its effects were highly significant (P<0.01), while for crispiness and overall acceptability, the effects were significant (P<0.05). As for sage extract, the level of this antioxidant had a highly significant (P<0.01) effect on appearance and taste and a significant effect (P<0.05) on odor and overall acceptability, but had no effect on crispiness. Although there was no significant synergistic correlation between citric acid and oleoresin rosemary extract or sage extract at the first order, its second order was significantly (P<0.05) related to taste, crispiness, and overall acceptability. An interaction between oleoresin rosemary and sage extracts also significantly (P<0.05) improved the score of overall acceptability of the potato chips. Contour maps of the sensory scores of potato chips indicated that the optimal points for appearance were achieved using 0.062% oleoresin rosemary extract, 0.066% sage extract, and 0.023% citric acid, while optimal task was achieved with 0.063% oleoresin rosemary extract, 0.075% sage extract, and 0.025% citric acid. With the same sequence of ingredients added into oil, the combinations required to achieve the optimal odor, crispiness, and overall acceptability scores were 0.058-0.046-0.026, 0.060-0.071-0.022, and 0.060-0.064-0.026%, respectively.     

Production of β‐galactosidase from recombinant Saccharomyces cerevisiae grown on lactose

Improved productivity and costs reduction in fermentation processes may be attained by using flocculating cell cultures. The production of extracellular heterologous β‐galactosidase by recombinant flocculating Saccharomyces cerevisiae cells, expressing the lacA gene (coding for β‐galactosidase) of Aspergillus niger under the ADHI promotor and terminator in a bioreactor was studied. The effects of lactose concentration and yeast extract concentration on β‐galactosidase production in a semi‐synthetic medium were analysed. The extracellular β‐galactosidase activity increased linearly with increasing initial lactose concentrations (5–150 g dm^?3). β‐Galactosidase production also increased with increased yeast extract concentration. During the entire fermentation, no accumulation of the hydrolysed sugars, glucose and galactose, was observed. The catabolic repression of the recombinant strain when cultured in a medium containing equal amounts of glucose and galactose was confirmed. In complete anaerobiosis, the fermentation of lactose resulted in a very slow fermentation pattern with lower levels of β‐galactosidase activity. The bioreactor operation together with optimisation of culture conditions (lactose and yeast extract concentration) led to a 21‐fold increase in the extracellular β‐galactosidase activity produced when compared with preliminary Erlenmeyer fermentations. Copyright © 2004 Society of Chemical Industry     

Scalable production of hydrophobic starch/beeswax films by continuous solution casting

Starch is an appealing natural polymer for the scaled-up production of biodegradable plastics. However, the low water resistance of starch has made its broad applicability largely doubted. In this study, starch was combined with beeswax (BW) through a pilot scale continuous solution casting (CSC) technique to reduce water affinity while keeping the ensuing films totally biodegradable. The phase morphology, surface wettability, and water vapor permeability (WVP) of films were examined over a broad BW–starch mass ratio (0.3–0.7). Emulsified, surfactant-free starch/BW films were successfully obtained at a productivity of 0.55 m² film h⁻¹. The water contact angle increased nearly by 100% at 30 wt% BW, leading to remarkable reductions in WVP. BW droplets well distributed within the starch matrix played a key role in enhancing the water barrier properties of films. CSC of starch/BW films offers a basis to design new hydrophobic formulations for applications that require biodegradable plastics with high moisture resistance.     

The antifungal activity and biotransformation of diisophorone by the fungus Aspergillus niger

The microbial transformation of racemic diisophorone was investigated using the plant pathogen Aspergillus niger as a biocatalyst. Incubation of diisophorone with Aspergillus niger gave 8α‐hydroxy‐diisophorone, 10‐hydroxydiisophorone and 17‐hydroxydiisophorone on the basis of their spectroscopic data including two‐dimensional NMR analysis, nOe and an X‐ray crystallographic study. The antifungal activity of diisophorone against Aspergillus niger was also examined. Copyright © 2004 Society of Chemical Industry     

Effect of dual chemical modification on the properties of biodegradable films from achira starch

The objective of this study was to evaluate the effect of a dual modification (acid hydrolysis and succination) on the structural, mechanical, thermomechanical, and permeability properties of films from achira starch. Micrographs of films revealed a smooth surface and some remnants of starch granules, indicating a partial gelatinization. Tensile strength and percentage of elongation increased in films from double modified starch (10.50 MPa and 42.83%, respectively). The OH groups formed in the amylose and amylopectin chains during the hydrolysis and the alkoxide groups (R O⁻) generated during the succination resulted in high values of water vapor permeability (3.215 × 10⁻¹⁰ g/s m Pa). The glass transition temperature (T_g) of films from hydrolyzed–succinated starch was decreased due to the reduction of the molecular weight of the polymeric chains and the presence of succinate groups that reduced the molecular interactions of the polymeric chains, increasing the mobility and therefore decreasing the softening temperature.     

Swelling and rheology of saponified starch–g–polyacrylonitrile copolymers. Effect of starch granule pretreatment and grafted chain length

A series of well-characterized starch–g–polyacrylonitrile (PAN) graft copolymers was prepared from corn starch which had been heated in water at temperatures up to 94°C to vary the extent of starch granule swelling and disruption. Graft polymerization onto gelatinized starch gave less frequent grafting of higher molecular weight PAN than comparable graft polymerizations onto ungelatinized starch. A graft copolymer was also prepared from gelatinized starch under high dilution conditions to give lower molecular weight grafted PAN and more frequent grafting. Graft copolymers were then saponified with sodium hydroxide to convert nitrile substituents to a mixture of carboxamide and sodium carboxylate. Saponified graft copolymers were only partially water soluble and consisted largely of highly swollen, insoluble gel, which was separated from solubles for the study of physical properties. Saponification mixtures were also dried to yield highly absorbent polymer films. With the exception of the graft copolymer prepared under high dilution conditions, the physical properties of saponified graft copolymers depended on whether or not the granules of starch were gelatinized before graft polymerization. Compared with saponified graft copolymers derived from ungelatinized starch, those prepared from gelatinized starch gave films that absorbed larger amounts of aqueous fluids. Also, the gel fractions from these saponified gelatinized polymers exhibited higher water swelling, lower shear modulus, and a lower reduced viscosity function (η/cQ). The saponified graft copolymer prepared from gelatinized starch under high dilution conditions more closely resembled those prepared from ungelatinized starch, suggesting that molecular weight of grafted PAN and the grafting frequency rather than starch granule pretreatment might be the most important factor which influences properties.