Identification of kafirin film casting solvents

The sorghum prolamin protein, kafirin can be used for making edible films. Several food compatible solvents were examined to identify novel kafirin film casting solvents to replace aqueous ethanol, commonly used for prolamin film casting. Glacial acetic acid and lactic acid were identified as the best primary solvents and 55% (w/w) aqueous isopropanol as a good binary solvent. However, the low volatility of the latter two prevents their use as casting solvents. Films could be cast from glacial acetic acid at 25 °C, a much lower temperature than the 70 °C required with aqueous ethanol. The sensory, tensile, and water barrier properties of the films cast from glacial acetic acid at 25 °C and aqueous ethanol at 70 °C were almost the same. However, the use of glacial acetic acid at 25 °C for casting kafirin films is advantageous as it gave films of more consistent quality.     

Physical properties of PVOH/chitosan-blended films cast from different solvents

Homopolymer films of chitosan and polyvinyl alcohol (PVOH) and blended films consisting of PVOH and chitosan were cast from different organic acid solvents: acetic acid (AA), citric acid (CA), lactic acid (LA) and malic acid (MA) and characterized for mechanical and barrier properties. Intermolecular interactions were investigated with FTIR. Cross-linking and interactions with the solvent system resulted in a wide range of properties. Also, the effect of blends and acid solvent on the mechanical properties [tensile strength (TS), % breaking elongation (%BE)] and barrier properties [water vapor permeability (WVP)] was investigated. The organic acid used as a solvent affected mechanical properties and the WVP of PVOH/chitosan films blends. TS and %BE of PVOH/chitosan films were 13.5–221.9 Mpa and 5.2–451.8%, respectively. The WVP ranged from 0.19 to 0.62 ng m/m² s Pa. The range of properties, both intermediate from the component polymers and extending beyond either individual component suggests molecular interactions and cross-linking within the blends. Elucidation of these interactions continues.     

Properties of Chitosan Films as a Function of pH and Solvent Type

ABSTRACT: Two different deacetylated chitosans were dissolved in formic, acetic, lactic, or propionic acid to prepare chitosan films. The pH values of the film-forming solutions were adjusted to 3, 4, and 5. Water vapor permeability (WVP), tensile strength (TS), elongation (E), and total soluble matter (TSM) were significantly ( P < 0.05) affected by acid type, pH, and degree of deacetylation (DA). Low DA (LDA) chitosan films had lower WVP and TSM, higher TS compared with high DA (HDA) chitosan films. The E values were not affected by DA. As pH increased, WVP and TSM of chitosan films tended to increase while TS decreased significantly ( P < 0.05). Chitosan films with acetic and propionic acid solvents had low WVP and TSM and high TS, while films with lactic acid solvent had high E and TSM and the lowest TS. Fourier-transform infrared showed peak shifting in the spectra with different solvents and at different pH values. Chitosan films with lactic acid solvent showed a peak shift to a lower frequency range. The NH₃⁺ band was absent in the pH 5.0 chitosan film spectra.     

Sorption Behavior of Crawfish Chitosan Films as Affected by Chitosan Extraction Processes and Solvent Types

Effects of chitosan extraction processes and solvent types on sorption behavior of unplasticized crawfish chitosan films were investigated. Four different chitosans prepared from crawfish shell were dissolved in 1% v/v acetic, formic, lactic, or malic acids at 1% w/v concentration. Chitosans dissolved in acetic or formic acid formed flexible and transparent films that are desirable for packaging applications. Chitosan acetate films maintained lower moisture contents at any relative humidity level compared with chitosan formate films. The type of chitosan significantly influenced the sorption isotherms of chitosan formate films but not chitosan acetate films. The Guggenheim‐Anderson‐de Boer, Oswin, and Caurie models (R²= 0.98, 0.95, and 0.95, respectively) could be used to predict sorption behavior of crawfish chitosan acetate and formate films.     

Characteristics of Different Molecular Weight Chitosan Films Affected by the Type of Organic Solvents

ABSTRACT: Chitosan films were prepared using 3 chitosan molecular weights and 4 organic acid solvents without plasticizer. Tensile strength (TS) and elongation (E) ranged from 6.7 to 150.2 MPa, and from 4.1 to 117.8%, respectively. Water vapor permeability (WVP) and oxygen permeability (OP) ranged from 0.3 to 0.7 ng-m/m²-s-Pa and OP from 0.4 to 5.8 × 10 ⁻⁸ cc/m²-day-atm, respectively. TS increased with chitosan molecular weight. Acetic acid resulted in the toughest films followed by malic, lactic, and citric acid, respectively. Films prepared with citric acid had the highest E values. WVP was not influenced significantly by the molecular weight of chitosan. OP of films prepared with malic acid was the lowest, followed by acetic, lactic, and citric acid.     

Preparation and characterization of kafirin‐quercetin film for packaging cod during cold storage

This study mainly evaluated the physical properties of kafirin‐quercetin (KQ) edible films and their application on the quality of cod fillets during cold storage. The results showed that the addition of quercetin significantly increased mechanical properties of KQ films, while decreased water vapor permeability, water solubility, and transparency. As quercetin was 0.4% (wt/vol), the film had the highest tensile strength (4.96 ± 1.23 MPa), the lowest water vapor permeability (1.08 ± 0.09 g·mm·m^?2·h·KPa^?1) and water solubility (22.02 ± 0.45%). Moreover, compared with the pure kafirin and polythylene films, KQ films could effectively inhibit the cod meat deterioration by restraining the growth of microorganisms and decreasing TVB‐N and TBARs. The KQ_0.4% film was the best to prolong the shelf life of cod fillets during cold storage. Therefore, KQ edible films could be used as a potential food packaging material to protect and retain the quality of aquatic products.     

Effect of Molecular Weight,Acid, and Plasticizer on the Physicochemical and Antibacterial Properties of β‐Chitosan Based Films

Abstract: Effects of chitosan molecular weight (1815 and 366 kDa), type of acid (1% acetic, formic, and propionic acid, or 0.5% lactic acid) and plasticizer (0, 25% glycerol or sorbital w/w chitosan) on the mechanical, water barrier, and antibacterial properties of β‐chitosan films were investigated. Tensile strength (TS) of high molecular weight (Hw) films was 53% higher than that of low molecular weight (Lw) ones, acetate, and propionate films had the highest TS (43 and 40 MPa) among tested acids, and plasticizer‐reduced film TS 34%. Film elongation at break (EL) was higher in Hw films than in Lw ones, in which formate and acetate films were the highest (9% and 8%, respectively), and plasticizer increased the film EL 128%. Molecular weight of chitosan did not influence water vapor permeability (WVP) of the films. Acetate and propionate films had lower WVP than other acid types of films, and plasticizer increased film WVP about 35%. No difference was found between glycerol and sorbitol films in terms of film mechanical and water barrier properties. Lw β‐chitosan films showed significant antibacterial activity against E. coli and L. innocua. This study demonstrated that β‐chitosan films are compatible to α‐chitosan films in physicochemical properties and antibacterial activity, yet with simple sample preparation. Practical Application: β‐chitosan based edible films at molecular weight of about 300 kDa showed great antibacterial activity against Gram‐positive and Gram‐negative bacteria. The films have similar mechanical and water barrier properties to α‐chitosan based films at the similar molecular weight, but simple sample preparation procedures and more attractive color. The release of active chitosan fragment from the film matrix acts as an antibacterial agent, making β‐chitosan films suitable as intelligent food wraps or coatings for a wide range of food products to control moisture loss and prevent surface bacterial growth.     

Inhibition of surface spoilage bacteria in processed meats by application of antimicrobial films prepared with chitosan

A study was undertaken to evaluate the feasibility of using antimicrobial films, designed to slowly release bacterial inhibitors, to improve the preservation of vacuum-packaged processed meats during refrigerated storage. The antimicrobial films were prepared by incorporating acetic or propionic acid into a chitosan matrix, with or without addition of lauric acid or cinnamaldehyde, and were applied onto bologna, regular cooked ham, or pastrami. At various times during storage, packages were opened and the amounts of antimicrobial agents remaining in the chitosan matrix were measured. Regardless of film composition or meat product type, propionic acid was nearly completely released from the chitosan matrix within 48 h of application, whereas release of acetic acid was more limited, with 2-22% of the acid remaining in chitosan after 168 h of storage. Addition of lauric acid, but not cinnamaldehyde, to the chitosan matrix generally reduced the release of acetic acid significantly (P < or = 0.05) and the release was more limited onto bologna than onto ham or pastrami. In addition, the efficacies of the various films for inhibiting bacterial growth were tested against indigenous lactic acid bacteria and Enterobacteriaceae, and against Lactobacillus sakei or Serratia liqueficiens, surface-inoculated onto the meat products. Whereas lactic acid bacteria were not affected by the antimicrobial films under study, the growth of Enterobacteriaceae and S. liquefaciens was delayed or completely inhibited as a result of film application. Strongest inhibition was observed on drier surfaces (bologna), onto which acid release was slower, and with films containing cinnamaldehyde, as a result of its greater antimicrobial activity under these conditions.     

葡萄酵素发酵过程中代谢产物的动态变化

为探究葡萄酵素接种发酵过程中物质变化规律,以葡萄为原料,分析了接种酵母菌、醋酸菌以及乳酸菌发酵过程中总酸、有机酸、乙醇体积分数、总酚、主要功效酶（超氧化物歧化酶及β-葡萄糖苷酶）以及香气成分等代谢产物的变化。结果表明：发酵过程中总酸质量浓度呈先上升后下降的趋势,于第34天达到最大值19.37 g/L;在接种酵母菌（0～6 d）发酵过程中有机酸主要以柠檬酸、苹果酸、酒石酸为主,且乙醇主要产生于该阶段;接种醋酸菌后（6～27 d）主要产生乙酸;而后接种乳酸菌后（27～41 d）,乳酸、柠檬酸质量浓度逐渐增加至最大值102.09 mg/L和67.70 mg/L,而苹果酸减少,此时乙醇体积分数降低至最小值0.47%并趋于稳定;总酚含量与β-葡萄糖苷酶活力的变化趋势一致,主要于接种酵母菌（0～6 d）发酵以及接种乳酸菌发酵后期（34～41 d）产生,超氧化物歧化酶活力总体呈波动上升趋势;葡萄酵素发酵过程中产生的挥发性物质主要以醇类、酸类和酯类化合物为主。以上研究结果可为葡萄酵素的精准制备以及品质优化提供理论依据。     

发酵前后甜石榴汁中有机酸的变化研究

本试验利用反相液相色谱（RP-HPLC）法分离测定发酵前后甜石榴汁中有机酸种类和含量。在甜石榴汁中检测到的有机酸包括草酸、苹果酸、α-酮戊二酸、乳酸、乙酸、柠檬酸与富马酸,其中主要有机酸为乳酸（占总有机酸的51.2%）、草酸（占总有机酸的26.8%）和柠檬酸（占总有机酸的16.8%）。发酵后甜石榴汁中的草酸与乳酸含量下降,乙酸含量增加,新生成酒石酸、丙酮酸与琥珀酸;苹果酸与柠檬酸含量增加。发酵后甜石榴汁的有机酸总量下降了7.8%.     

Preparation of tofu using chitosan as a coagulant for improved shelf-life

The potential of chitosan as a coagulant in commercial tofu preparation was investigated with six chitosans of different molecular weights using various treatments. The following optimum processing conditions for tofu preparation were proposed: chitosan with a molecular weight of 28 kDa; chitosan solution type, 1% chitosan/1% acetic acid; chitosan solution to soymilk ratio, 1 : 8; coagulation temperature, 80 °C; coagulation time, 15 min. However, the sensory quality of tofu was notably improved using a 1 : 1 mixture of 1% acetic acid and 1% lactic acid instead of 1% acetic acid alone as a chitosan solvent. Tofu prepared with chitosan had lower ash and higher protein content than those of commercial products tested. In storage tests, the chitosan‐tofu had a longer shelf‐life, about 3 days, than tofu made with CaCl₂. This added shelf‐life is significant in view of the magnitude (366 000 tonnes year^?1) of tofu produced from commercial tofu plants (1407 plants as of 1998) in Korea.     

Properties and release kinetics of pine bark incorporated agar and carrageenan film

Effects of plasticisers (glycerol, sorbitol and polypropylene glycol) and blend ratios on release behaviour, molecular vibration, mechanical and water barrier properties in agar and carrageenan films incorporating pine bark extract were investigated. Infrared spectra indicated hydrogen bonding of sorbitol and polypropylene glycol with film polymers which improved water diffusion and agar solubility but showed no effect in carrageenan films due to high water affinity. Hydrophilicity of the plasticisers modified dissolution of films and strongly affected the release behaviours of polyphenols and antioxidant capacity (DPPH• and FRAP). Film solubility showed high correlation to release behaviours. Fick’s diffusion kinetics fitted well to release behaviour of pine bark to aqueous media (water, 3% acetic acid and 10% ethanol). Agar gave a higher diffusion coefficient that was improved by the addition of sorbitol and polypropylene glycol. Increased diffusion coefficients enhanced degree of release, with some diversions suggesting that solvent modified matrices and, hence, release properties.     

Effect of storage time and temperature on structure,mechanical and barrier properties of chitosan-based films

The mechanical (tensile strength, elongation at break, mechanical work of deformation) and barrier (water vapor permeability and water vapor uptake) properties of chitosan films produced with acetic and lactic acids have been studied as a function of storage time, molecular weight of chitosans, concentration of plasticiser and the storage temperature. It was demonstrated that mechanical properties of chitosan-based films can be improved to a great extent during storage at low temperatures in freezer and refrigerator. Transition of chitosan molecules during storage in the solid state to more extended conformations and free volume changes are considered as mechanisms for the improvement of mechanical and barrier properties of chitosan films. The best mechanical properties are achieved for chitosan films produced with acetic acid and plasticized by the addition of 20% of glycerol. Sharp decrease in water vapor permeability has been demonstrated for thinner chitosan films and related to more dense packing and orientation of linear chitosan macromolecules.     

Effect of freezing on physical properties of whey protein emulsion films

The objective of this work was to study the effect of the freezing process on physical properties of whey protein emulsion films with different beeswax content dried at 5 °C. Thickness, microstructure, water vapour permeability, solubility in water, sorption isotherms and mechanical properties were measured in Control and Frozen films. The freezing process did not cause fractures or perforations in films, but films with beeswax showed a change in the appearance of the lipids after freezing. Only films with 40% of beeswax showed a significant increase in the water vapour permeability after freezing. The freezing process did not affect film solubility in water but produced small differences in the equilibrium moisture content values. In the puncture test, the freezing process increased puncture strength and deformation of films without beeswax but those parameters were not affected in films with beeswax. In tensile test, tensile strength and elastic modulus decreased, but elongation was not affected by freezing process. Principal component analysis accomplished an adequate condensation of the date grouping samples according to film formulation and treatment (Control and Frozen films). Indeed, the relationships of sample grouping and measured parameters were enlightened by principal component analysis. In conclusion, whey protein emulsion films were resistant to the freezing process (freezing, frozen storage and thawing) and could be a good alternative as a treatment to preserve the quality of frozen foods.     

原汁苹果醋中的有机酸

以苹果汁为原料 ,采用液态酒精发酵和醋酸发酵法制作苹果醋 ,采用反相高效液相色谱法分析苹果醋中有机酸 ,研究了苹果品种、醋酸菌种、醋酸发酵方法及过程对有机酸的影响。认为苹果酸是苹果醋中的主要有机果酸 ,其与液态粮食醋有机酸组成的差别主要体现在苹果酸、酒石酸和乳酸的含量上 ,苹果品种是影响原汁苹果醋中有机酸的种类和含量主要因素 ,醋酸菌在醋酸发酵过程中有代谢各种有机酸的作用 ,发酵方法会影响醋酸菌对有机酸代谢作用的程度 ,试验中所采用的 5种醋酸菌在醋酸发酵过程中通过消耗苹果酸、乳酸、琥珀酸 ,而产生和积累柠檬酸。     

Development of bioactive edible film from turmeric dye solvent extraction residue

We developed and characterized turmeric flour films using the turmeric dye solvent extraction residue. We evaluated how the heating temperature and pH affected film properties using a 2² central composite design. Multi-response analysis furnished the film formulation that offered larger resistance to break, as well as lower water solubility, WVP, and opacity. The heating temperature and pH affected the mechanical properties, solubility, moisture content, WVP, and opacity of the resulting film. High heating temperature promoted more interactions between the polymers present in the turmeric flour (starch, protein, lipid, and fiber), affording a more resistant polymeric structure with lower WVP, moisture content, and opacity. Higher pH values also favored a more mechanically resistant and dense matrix with lower water solubility and WVP. The optimized conditions were: T = 86.7 °C and pH = 8.5. The films produced under these conditions displayed high mechanical strength (18 MPa), low solubility (36%), and low WVP (0.167 g mm h⁻¹ m⁻² kPa⁻¹). However, because these films contained lignocellulosic fibers, they presented low elongation at break (1.8%), which elicited a non-continuous structure. HPLC and DPPH assays showed that the turmeric dye solvent extraction residue can be a promising source to develop films with antioxidant activity.     

Chitosan Treatment Affects Yield, Ascorbic Acid Content, and Hardness of Soybean Sprouts

ABSTRACT: The effects of molecular weights, concentrations and solvents of chitosan, soaking times, and soybeans/chitosan solution ratios on growth and quality of soybean sprouts were investigated. Among 5 chitosans, treatment with 493 kDa chitosan was the most effective in increasing total weight, vitamin C content, and hardness. Use of acetic acid rather than lactic acid as a chitosan solvent increased hypocotyl weight and vitamin C content. Soaking of soybeans in chitosan solution for 8 h increased total weight by 13% and vitamin C content by about 10%. Optimal cultivation conditions involve soaking in 0.05% chitosan with 493 kDa in 0.05% acetic acid for 8 h and a soybean/chitosan solution ratio of 1:4.     

Effects of various plasticizers on mechanical and water vapor barrier properties of gelatin films

Different kinds of plasticizers were chosen to study the effects of plasticizer composition, size and shape on the mechanical properties and water vapor permeability (WVP) of gelatin films in this paper. Firstly, oligosaccharides – sucrose, and some organic acids such as oleic acid, citric acid, tartaric acid, malic acid (MA) were added to gelatin. It was found that only MA could improve the ductility of gelatin film, and the visual appearance of MA modified gelatin film was better. Secondly, polyethylene glycols (PEG) with different molecular weights (300, 400, 600, 800, 1500, 4000, 10?000, 20?000) were used to plasticize gelatin films. This showed that PEG of lower molecular weights exhibited better plasticizing effect for gelatin films, and such films had better visual properties. This shows that mannitol (Man) and sorbitol (Sor) could make gelatin films flexible, whereas Man could crystallize from gelatin film. Following this, the plasticization of ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG) series and ethanolamine (EA), diethanolamine (DEA), triethanolamine (TEA) series was studied. At last, suitable plasticizers (MA, PEG300, sorbitol, EG, DEG, TEG, EA, DEA, TEA) for gelatin were selected to investigate the WVP and water content of these plasticized gelatin films. The mechanical properties of these films were also compared.     

小麦麦芽制麦过程中酸感物质的变化

为了能够更好地了解小麦麦芽在不同制麦阶段酸感物质的变化,为小麦麦芽制麦工艺的优化提供技术参考,本研究选取琥珀酸、乙酸、柠檬酸、苹果酸和乳酸作为酸感物质的代表,按照微型制麦工艺对样品进行制麦操作,采用高效液相色谱~（HPLC）对不同制麦时间的酸感物质进行检测分析,结果发现：小麦在发芽期间,总酸感物质含量逐渐升高;苹果酸在整个制麦过程一直处于动态平衡过程中;乙酸、乳酸、柠檬酸和琥珀酸都随时间逐渐升高,较小麦分别增加了11．2倍、6．1倍、7．0倍、4．7倍,且都在发芽阶段时大量增加。     

Effect of Plasticizer Concentration and Solvent Types on Shelf-life of Eggs Coated with Chitosan

ABSTRACT:  Effects of plasticizer concentrations (0, 0.5, 1.0, 1.5, and 2.0% glycerol) and solvent types (1% acetic and 1% lactic acid) on internal quality of eggs coated with 2% chitosan solution were evaluated during 5 wk of storage at 25 °C. In comparison of plasticizer concentrations, eggs coated with chitosan dissolved in acetic acid containing 2% glycerol showed significant reduction in weight loss compared with the noncoated eggs during 5 wk of storage. At 2% glycerol, the Haugh unit and yolk index values suggested that chitosan-coated eggs can be preserved for at least 3 wk longer than the control noncoated eggs during 5 wk of storage at 25 °C. Use of acetic acid rather than lactic acid as a chitosan solvent was more advantageous in view of shelf-life extension of eggs.