Natural antimicrobial ingredients incorporated in biodegradable films based on cassava starch

Biodegradable films based on cassava starch and with addition of natural antimicrobial ingredients were prepared using the casting technique. The tensile properties tensile strength (TS) [MPa] and percent elongation (E) at break [%] and the water vapor transmission (WVT) of the biodegradable films were evaluated and compared with the control (without antimicrobial ingredients). The evaluation of the Colony Forming Units per gram [CFU/g] of pan bread slices packed with the best biodegradable films, in terms of packaging performance, was also determined. The addition onto the matrix of only clove and cinnamon powders could reduce the films WVT when compared to the control, however TS and E were lower than the control and the effect of cinnamon was milder regarding this property. Since water activity of the pan bread slices packed with the biodegradable films increased considerably during the storage period, the antimicrobial effect could not be clearly determined.     

豌豆淀粉与马铃薯淀粉、玉米淀粉理化性质比较

通过对豌豆淀粉、马铃薯淀粉和玉米淀粉的基本组成、颗粒形态、凝沉性、糊化特性、透明度及抗性淀粉含量的测定与比较表明:豌豆淀粉中直链淀粉和蛋白质的含量较高,但其颗粒直径小于马铃薯淀粉;与马铃薯淀粉和玉米淀粉相比,豌豆淀粉易于回生,但糊稳定性较好;豌豆淀粉糊的透明度低于马铃薯淀粉,但其淀粉组成中慢消化淀粉含量高于马铃薯淀粉和玉米淀粉。      

Composite and bi-layer films based on gelatin and chitosan

The aims of this work were: to develop composite, bi-layer and laminated biodegradable films based on gelatin and chitosan, to determine film barrier and mechanical properties and to characterize their microstructure.Gelatin and chitosan concentrations used were 7.5% and 1% (w/w), respectively. Glycerol (0.75%) was added as plasticizer.Physicochemical properties such as moisture content, transparency and color were analyzed. Composite and bi-layer systems showed a compact structure indicating a good compatibility between components.Water vapor permeability (WVP) was independent of film thickness up to 120 μm for gelatin films and 60 μm for chitosan ones. Both, bi-layer and laminated systems resulted effective alternatives to reduce WVP of composite films (at least 42.5%). Bi-layer systems showed better mechanical properties than laminated ones. The resistance at break increased from 54.3 for composite to 77.2 MPa for bi-layer films, whereas elongation at break values of both composite and bi-layer films were similar (2.2–5.7%).     

壳聚糖/尼泊金酯共混膜的制备及性能研究

研究不同浓度的尼泊金酯对壳聚糖/尼泊金酯共混膜性能的影响,通过红外光谱(FT—IR)、扫描电镜(SEM)对共混膜结构进行表征,同时测定共混膜的厚度、透光性、色度、力学性能、水蒸气透过率、溶胀性和抑菌性能。结果表明,随着尼泊金酯浓度的增加,共混膜的透光性降低,颜色呈暗黄色。当尼泊金酯浓度为5%(WT)和25%(WT)时,拉伸强度和断裂伸长率最大,分别为37.0 MPa和55%;当尼泊金酯浓度为5%(WT)时,水蒸气透过系数最低,仅为7.5×10-14 g/(m2·s·Pa),该浓度下共混膜具有良好的阻气性和溶胀性。研究还发现共混膜对金黄色葡萄球菌和大肠杆菌的生长具有抑制作用,且高浓度尼泊金酯/壳聚糖膜对金黄色葡萄球菌的抑制效果更为明显,其抑菌圈直径可达10.8mm。     

高直链玉米淀粉/羟丙基甲基纤维素可食性膜的制备及性能研究

以高直链玉米淀粉(HACS)和羟丙基甲基纤维素(HPMC)为主要成膜基材,采用溶液流延法制备了HACS/HPMC可食性膜。研究了不同配比的HACS与HPMC对可食性膜的结晶性能、力学性能、亲水性能和水蒸气阻隔性能等的影响。结果表明,随着HPMC比例的增大,HACS与HPMC之间的氢键作用减弱,复合膜的水溶性增大,连续相由HACS转变为HPMC,但HACS与HPMC的相容性变差。HPMC可有效降低可食性膜的结晶程度并抑制其在储藏过程中的老化。在复合膜中,当HACS与HPMC比例为8∶2时,可食性膜具有最大抗拉强度(7.5 MPa)、断裂伸长率(14.7%)、水接触角(84.33°)和最低水蒸气透过系数(2.17×10~(-10 )g·m·m~(-2)·s~(-1)·Pa~(-1))。纯HACS膜和纯HPMC膜的透光性能均优于HACS/HPMC复合膜。     

Properties of wheat starch film-forming dispersions and films as affected by chitosan addition

In order to evaluate the impact of chitosan on the physical properties of wheat starch–glycerol films, part of the wheat starch was replaced by chitosan, and the effect of composition on the properties of both the films and the film-forming dispersions was studied. The latter became more stable and viscous as the chitosan proportion was increased in the mixture. Both polymers appeared to integrate homogeneously in the film matrix. The combined effect of the glycerol and chitosan proportions affected the mechanical and barrier properties of the films. The tensile strength and elastic modulus of the films were improved as chitosan ratio increased. The oxygen and water vapor permeability slightly increased in line with the amount of chitosan in the blend although the induced differences were very small. Chitosan ratio directly affected the antimicrobial properties of the films, which showed a significant bactericide activity when the chitosan–starch ratio in the film was 50%. Nevertheless, at a starch:chitosan ratio of 80:20, counts of coliforms did not exceed the initial value in the meat after 7 storage days.     

玉米淀粉与小麦淀粉复合可食用膜工艺研究

以玉米淀粉和小麦淀粉为成膜基质,采用流延法制备可食用膜,以膜的力学性能作为考查指标,通过单因素实验研究质量比、山梨醇含量、柠檬酸含量、增强剂含量、糊化温度、糊化时间对力学性能的影响,在单因素基础上,以四因素三水平的正交实验优化的最佳制膜工艺条件。结果表明,在淀粉溶液浓度60 g/L,玉米淀粉和小麦淀粉质量比40∶60,山梨醇含量0.6%,柠檬酸含量2.5%,增强剂含量1.4%,糊化温度85℃,糊化时间40 min,干燥4~6 h的最佳制膜工艺条件下,复合膜的拉伸强度为14~15 MPa,断裂伸长率为30%~33%。      

Extrusion parameters related to starch/chitosan active films properties

Despite the increased use of extrusion technology in the production of biodegradable films, a better understanding of its effects on the several biopolymers is required. Therefore, the influence of extrusion temperature (120, 130 and 140 °C) and screw speed (25, 35 and 45 r.p.m.) on the properties of an active film formulated with starch, chitosan and oregano essential oil was investigated. Mechanical and barrier properties, apparent opacity and blow‐up ratio (BUR) of films were determined. The increase in screw speed had a positive effect on BUR and water vapour permeability (WVP) and a negative effect on opacity, tensile strength and elongation at break of the films. Low die temperatures resulted in decreased tensile strength, elongation at break, Young’s modulus and WVP of the films. Sorption isotherms of films were directly influenced by the extrusion conditions and films produced at 130 °C and 35 r.p.m. were less hydrophilic.     

Antimicrobial and physical properties of sweet potato starch films incorporated with potassium sorbate or chitosan

Antimicrobial biodegradable films have been prepared with sweet potato starch by incorporating potassium sorbate or chitosan. Films incorporated with potassium sorbate ≥ 15% or chitosan ≥ 5% were found to have an anti-Escherichia coli effect. Staphylococcus aureus could be effectively suppressed by incorporation of chitosan at ≥10%. Whereas potassium sorbate lowers the tensile strength and elongation at break, and raises the oxygen permeability, water vapor permeability and water solubility, chitosan has the opposite effect. Fourier Transform Infrared (FT-IR) spectra analysis revealed that starch crystallinity was retarded by potassium sorbate incorporation and that hydrogen bonds were formed between chitosan and starch. This explained the modification of the mechanical and physical properties of the films by the incorporation of these two antimicrobial agents.     

乳化剂对高直链玉米淀粉/羟丙基甲基纤维素复合膜性能的影响

本文以高直链玉米淀粉（HACS）、羟丙基甲基纤维素（HPMC）为成膜基材制备可食性食品包装膜。为解决两者在制膜过程中的相分离问题,通过力学性能、水溶性、结晶性能和表面形貌的分析,研究乳化剂的种类（单甘酯、吐温80、十二烷基硫酸钠）和添加量（1%,2%,3%）对HACS/HPMC复合膜性能的影响。X-射线衍射（XRD）分析表明,乳化剂主要通过与直链淀粉形成V型结晶结构而影响HACS/HPMC复合膜的性能。红外光谱（FT-IR）分析表明,添加乳化剂增加HACS与HPMC之间的氢键相互作用。添加2%单甘酯的复合膜综合性能最优,抗拉强度和断裂伸长率分别提高到10.24 MPa和15.86%,复合膜的截面与表面光滑平整。研究证明添加2%的单甘酯可有效的提高HACS与HPMC在成膜过程中的相容性,得到性能优良的复合膜。      

机械力与柠檬酸双改性热塑性玉米淀粉的制备研究

以玉米淀粉为原料,经过超微粉碎,用柠檬酸与甘油作改性剂,合成双改性热塑性玉米淀粉,确定了双改性热塑性玉米淀粉合成工艺的最佳条件——原淀粉经超微粉碎,在反应温度120℃,反应时间60min,配料比m(含水20%的玉米淀粉):m(柠檬酸):m(甘油)=1:0.4:0.3下,双改性热塑性玉米淀粉的取代度是0.259,酯化度是0.346,均比单改性的大。红外光谱分析证实在淀粉中引入了柠檬酸酐,X-衍射揭示双改性淀粉的结晶度下降。     

玉米淀粉与小麦淀粉性能对比及纯棉纱上浆研究

通过大量实验对玉米淀粉、小麦淀粉的性能进行了测试研究，并探讨了以玉米、小麦淀粉为主浆料对纯棉纱上浆的浆纱质量，结果表明其上浆效果玉米淀粉略优于小麦淀粉。     

Antimicrobial activity of buckwheat starch films containing zinc oxide nanoparticles against Listeria monocytogenes on mushrooms

Buckwheat starch (BS) films containing zinc oxide nanoparticles (ZnO‐N; 0%, 1.5%, 3% and 4.5%) were prepared, and their physical, optical and antimicrobial properties were examined. As ZnO‐N content increased from 0% to 4.5%, TS increased from 14.99 to 19.09 MPa and E decreased from 25.60% to 20.65%. In addition, L* and a* values decreased, whereas b*, ΔE and opacity increased. Regarding antimicrobial activity, the BS/ZnO‐N films had the reductions of 2.96–3.74 log CFU mL^?1 against Listeria monocytogenes after 8 h based on viable cell count assay. The BS film containing 3% ZnO‐N, an optimal concentration chosen in this study, was applied to fresh‐cut mushroom packaging, and the film exhibited antimicrobial activity against L. monocytogenes, resulting in a reduction of 0.86 log CFU g^?1 after 6 days of storage. Thus, these results indicate that the BS/ZnO‐N film can be used as a biodegradable packaging material.     

Production and characterization of oxidized cassava starch (Manihot esculenta Crantz) biodegradable films

Plastic is one of the most common pollutants in the environment. Therefore, the number of studies on the use of biodegradable packaging is increasing. Starch is the primary material used in the production of biodegradable plastics due to its natural abundance and high biodegradability. Yet, the strong hydrophilic character of starch presents a challenge. Therefore, the modification of its structure through oxidation may yield interesting results as the viscosity reduction. The objectives of this work were to obtain cassava (Manihot esculenta Crantz) starch oxidized with 0.8 and 2.0% active chlorine, to develop biodegradable films and characterize their mechanical properties, solubility in water, permeability to water vapor, degree of swelling, and sorption isotherms. Biodegradable films were produced with starch concentrations of 2, 3, 4, and 5% w/w and 25% glycerol (g/100 g starch) added as a plasticizer. Images of the films were obtained with an atomic force microscope and allow to observe a smooth surface and the absence of starch granules in the film produced with oxidized starches. The tensile strength of the biodegradable film produced with oxidized starch (0.8% active chlorine) was 80 MPa. The value of permeability to water vapor was 1.613 × 10⁻⁹ kg/day/m/Pa, and the average solubility was 41%. The sorption isotherms showed that biodegradable films made with oxidized starches cannot be used in environments with relative humidity below 35% or above 90%.     

pH和双醛淀粉对罗非鱼鱼皮明胶膜性质的影响

考察了pH和双醛淀粉（DAS）对鱼皮明胶膜的机械性能和耐水性能的影响。结果表明,随着pH的升高,明胶膜的抗拉伸强度（TS）呈现先增加后降低的趋势,pH7时达到最大值（23.78MPa）,而膜的固形物溶解率（MS）和蛋白溶解率（PS）逐渐下降。当明胶膜添加了DAS后,膜的TS显著增大（p<0.05）,而MS和PS都显著下降（p<0.05）。另一方面,在pH7下,添加1.5%的DAS可有效提高膜的机械性能和耐水性能。SDS-PAGE分析结果表明,在成膜过程中pH对明胶蛋白组分没有产生明显的影响,DAS与明胶蛋白之间发生了交联反应。      

Preparation and properties of starch nanocrystals/carboxymethyl chitosan nanocomposite films

Waxy maize starch was hydrolyzed with sulfuric acid in aqueous solution. The remaining starch granules after acid hydrolysis were characterized by TEM and wide‐angle XRD. Starch nanocrystals with size between 40 to 80 nm and relative crystallinity of 63% were obtained after 6 days of hydrolysis. Starch nanocrystals/carboxymethyl chitosan composite films were prepared by casting‐evaporation method. When the starch nanocrystals content was below 30 wt%, the filler dispersed uniformly in the carboxymethyl chitosan matrix, whereas aggregation of starch nanocrystals and phase separation between aggregates and matrix were observed when the starch nanocrystals content was higher than 30 wt%. The maximum tensile strength (TS) of composite films approached ∼29 MPa, which was two times higher than that of the carboxymethyl chitosan film without filling starch nanocrystals. The percentage elongation at break (EB%) of nanocomposite films decreased with the increasing of the starch nanocrystals content. The water absorption and water vapor barrier property of carboxymethyl chitosan film were significantly improved by adding starch nanocrystals.     

氧化玉米淀粉/明胶复合胶囊壳的制备与表征

目的：采用改性淀粉与明胶共混制备胶囊壳,降低胶囊壳制备成本。方法：以玉米原淀粉为原料,采用15%用量的过氧化氢氧化制备氧化玉米淀粉,与明胶共混,分别通过流延法和浸渍法制备了氧化玉米淀粉/明胶复合胶囊膜和胶囊壳,并采用傅里叶变换红外光谱（FT-IR）、X射线衍射（XRD）、扫描电子显微镜（SEM）对其进行表征。结果：当氧化玉米淀粉与明胶质量比为5∶5,制备的氧化玉米淀粉/明胶复合胶囊壳的干燥失重在13.0%～15.0%,在蒸馏水和模拟人工胃液中的崩解时限在10 min以内,脆碎度不超过5粒。结论：采用氧化玉米淀粉与明胶共混制备的复合胶囊壳性能符合《中国药典》（2020）要求。     

Property improvement of thermoplastic mung bean starch using cotton fiber and low‐density polyethylene

Due to high water uptake and low mechanical properties of biodegradable thermoplastic starch, thermoplastic starch prepared from mung bean starch (TPMBS) was modified by the incorporation of cotton fiber and low‐density polyethylene (LDPE). The effect of different ratios of cotton fiber/LDPE, i.e., 10:0, 7:3, 5:5, 3:7, and 0:10, on water uptake, mechanical, thermal, and biodegradable properties of TPMBS was examined. Different TPMBS samples were prepared using internal mixer for compounding and compression molding machine for shaping samples. It was found that the TPMBS incorporated with 10:0, 7:3, and 3:7 cotton fiber/LDPE showed an increase in the stress at maximum load and Young's modulus. Moreover, the water absorption of all of the modified TPMBS samples tended to decrease as compared to the pure TPMBS. Morphological, thermal, and biodegradable properties of different TPMBS samples were also investigated.     

发芽对普通玉米和糯玉米淀粉理化特性的影响

以普通玉米和糯玉米种子为材料,进行不同发芽时间处理,分析发芽对其淀粉理化特性的影响。结果表明,与CK（未发芽处理）相比,两种类型玉米发芽后淀粉溶解度和淀粉糊透光率增大,且随着发芽时间的延长而升高;蓝值、碘结合力和膨润力减小,且随着发芽时间的延长而降低。普通玉米发芽36 h时淀粉胶凝化和回生参数最高;发芽后糯玉米淀粉的胶凝化温度降低,胶凝化焓值、回生焓值和回生值随发芽时间的延长先升高后降低,在发芽48 h时最高。发芽提高了两种类型玉米淀粉的结晶度,普通玉米淀粉结晶度和尖峰强度在发芽60 h时最高,糯玉米在48 h最高。因此,发芽可以作为改变淀粉理化特性的手段,为玉米的加工利用提供参考。