Effect of Stearic Acid on Barrier and Mechanical Properties of Edible Films Based on Carboxymethyl Cellulose (CMC), Konjac Glucomannan (KGM), and κ-Carrageenan (κCarr)

The objectives of this research were to improve the film-forming properties of Channel Catfish Ictalurus punctatus skin gelatin (CSG) by cross-linking with transglutaminase (TG), determine and optimize the TG reaction time, and characterize the mechanical and barrier properties of CSG edible film. Cross-linking of CSG was performed by TG for 0, 10, 20, 30, and 40 min at 50°C, and the reaction was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The color and mechanical and barrier properties of edible films fabricated with CSG cross-linked with TG were characterized. Gelatin yields from the extraction ranged from 18.2% to 23.3%. SDS-PAGE exhibited dark bands at 120 and 250 kDa, indicating successful TG-mediated cross-linking. The color of CSG film was not affected by TG cross-linking. The tensile strength of CSG films cross-linked with TG decreased from 42.59 to 21.73 MPa and the percent elongation increased from 42.92% to 76.96% as reaction times increased from 0 to 40 min. There was no significant difference in water vapor permeability of CSG films.

Many factors influence physical properties of edible composite films fabricated from hydrocolloids and lipids. Novel edible emulsified films were made using PGP, glycerol and stearic (SA) or oleic (OA) fatty acids by Tween-80 addition and emulsification of filmogenic solutions. In this study, the effect of physical state of fatty acids on the pistachio globulin protein (PGP) edible film properties was investigated. There were significant differences (p < 0.05) in the water vapor permeability (WVP), tensile strength (TS) and opacity of emulsified films containing SA and OA. SA was more effective than OA in WVP diminishing. The decrease values of 42 and 26.5% were observed for films with SA and OA, respectively. TS and elongation at break values of films containing OA were lower than SA ones. Oxygen permeability (OP) was evaluated indirectly applying peroxide value measurement. No significant difference was observed in the OP of the films. Water solubility was not affected by the physical state of fatty acids either. The solid state of SA at the room temperature caused the resultant films to be more opaque than OA containing films. Our findings indicated that PGP films modified with SA had better physical properties special in WVP reduction than OA ones and could be potentially used for primary packaging of foods with high water loss problem.

در تحقیق حاضر بمنظور بهبود خواص فیزیکی و مکانیکی فیلم‌های زیست تخریب‌پذیر خوراکی ترکیب کردن دو پلیمر کربوکسی‌متیل‌سلولز (CMC) و کتیرا مورد مطالعه قرار گرفت. کربوکسی‌متیل‌سلولز و کتیرا با نسبت‌های 25:75، 50:50 و 75:25 با یکدیگر ترکیب شده و میزان نفوذپذیری به بخار آب، درصد حلالیت، خواص مکانیکی و ریزساختار آنها ارزیابی گردید. نتایج نشان داد که در میان سه نسبت مرکب دو پلیمر، میزان استحکام کششی در نسبت 50:50 نسبت به دو ترکیب دیگر بیشتر بود طوری که مقدار آن در نسبت های 50:50، 25:75 و 75:25، به ترتیب 59/44، 82/32 و 59/26 مگاپاسکال بوده است. نفوذپذیری به بخار آب در ترکیب 50:50 و 75:25 نسبت به ترکیب 25:75 از شرایط بهتری برخوردار بود. ویژگی حلالیت در آب در سه فیلم ترکیبی تفاوتی با یکدیگر نداشتند ولیکن دارای کیفیت بهتری نسبت به فیلم خالص CMC بودند طوری که مقدار 52 الی 58 درصد نسبت به فیلم خالص CMC کاهش معنی‌داری را در میزان حلالیت به نمایش گذاشتند. همچنین، ترکیب کردن دو پلیمر در نسبت‌های مختلف توانست از میزان حساسیت فیلم‌ها نسبت به رطوبت بکاهد. بطورکلی، از نتایج این تحقیق دریافت می شود که ترکیب کردن دو پلیمر می تواند برخی ویژگی‌های فیزیکی- مکانیکی فیلم خوراکی تهیه شده از کربوکسی‌متیل‌سلولز- کتیرا را بهبود بخشد.

Farm-raised catfish are important to the economy of the southeastern states in the United States, and catfish processing produces about 55% of by-products for inexpensive sale. Therefore, the utilization of catfish by-products is of great interest to the catfish industry. The objectives of this research were to determine the optimum pretreatment method to extract catfish gelatin for edible film application, and to characterize physical, mechanical, and barrier properties of edible films fabricated with catfish skin gelatin. Catfish skins obtained from a local plant were treated with 6 selected pretreatment methods. The main extraction was performed with deionized water at 50 degrees C after pretreatment. The gelatin yield was calculated and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was performed to characterize molecular weight (MW) profile. Color, tensile strength (TS), elongation, and water barrier property were determined to characterize the fabricated catfish gelatin films. From the results of gelatin yield, color, SDS-PAGE, as well as mechanical and barrier properties of the film, the pretreatment method with 0.25 M NaOH and 0.09 M acetic acid, followed by extraction at 50 degrees C for 3 h, was determined as the optimum extraction method. The catfish gelatin exhibited higher MW fractions than commercial mammalian gelatin. The catfish gelatin extracts possessed film-forming properties determined by TS, elongation, and water vapor permeability (WVP) comparable to those of commercial mammalian gelatin. The selected formula for catfish gelatin film was determined as 1% gelatin and 20% glycerol, resulting in greatest TS and lowest WVP.

High pressure homogenization of mechanically deboned chicken meat protein suspensions to improve mechanical and barrier properties of edible films

Indian jujube (Ziziphus mauritiana Lamk) fruit also known as “Ber” has been a useful fruit in India from age‐old days. It contains antioxidant, anti‐inflammatory, and antibacterial properties, additionally they are rich in vitamin C, thiamine, riboflavin, etc. The jujube puree was used for developing edible films along with varying concentrations of pectin (1, 2, 3, 4, and 5%). The edible films on characterization show that a rise in pectin concentration helps to improve the tensile strength of the film from 54.55 to 472.32 kPa. But the stability or water tolerance of the films were negatively affected by a rise in pectin concentration. The solubility of films was increased to 83.32% from 76.77%. Properties like color, water activity, and water vapor permeability were less affected with the addition of pectin. The work leads to the successful development of jujube puree—pectin‐based edible film that can create a positive influence on film mechanical and barrier properties. The properties of these edible films can be further improved with the administration of suitable cross‐linking agents or bioactive compounds.Practical ApplicationsIndian jujube is a seasonal fruit and generally available for a very short duration mostly from January to April and mostly consumed as raw. The pulp and peel of this fruit are rich in different bioactive compounds. As the fruit is highly perishable major fraction of the total yield gets wasted every year. It is not yet commercially explored to make value‐added products. The development of edible films from these fruit purees helps to introduce novel colors and flavors to the edible film research. The film composition used in the study can also be adapted for coating perishable fruits by spraying, which helps to add barriers to its spoilage. It can also help to increase the nutrition and quality of the product for which the film is used. The study helped to understand the potential of jujube fruit as a novel edible packaging material and opened new opportunities to utilize the indigenous varieties of seasonal fruits that are not celebrated in the market.

Edible film is potentially applied to replace non-biodegradable packaging for animal products, e.g. meat and meat products. The overall objective of this study was to observe the effect of different addition levels of modified casein hydrolysate (casein-catechin complexes) on mechanical (film thickness, water vapor permeability, tensile strength, elasticity), chemical (moisture content, water activity, and solubility) and microstructure properties of composite edible casein film. The edible films were formulated according to different combinations of modified casein hydrolysate and casein film solution (0.50:0.25, 0.50:0.50, 0.75:0.25, and 0.75:0.50) and compared with control (without addition of modified casein). No significant effects of the treatment were found on film thickness, water vapor permeability, tensile strength, elasticity, moisture content, water activity, and solubility of the composite edible film. However, the micrographs show that the amount of polymer was higher as the proportion of catechin was increased. In conclusion, the addition of catechin-added casein (modified casein) to casein edible film solution at up to 0.5% did not alter the mechanical properties, moisture content, water activity and solubility of the composite edible film.

Background: Edible films and coatings are biodegradable that can preserve the quality and extend the shelf life of foods. The aim of this study was to investigate the physical and mechanical properties, and antimicrobial activity of carboxymethyl cellulose (CMC) film containing Artemisia sieberi Essential Oil (AEO). Methods: The studied parameters were the antibacterial activity and physical properties, including Water Vapor Permeability (WVP), Contact Angle (CA), solubility, Moisture Content (MC), and surface color; as well as mechanical properties including Elongation at break% (E%) and Tensile Strength (TS) of CMC incorporated with AEO at levels of 0 (control), 0.5, 1, and 1.5% v/v. Data were statistically analyzed by SPSS software. Results: Camphor (36.38%), 1,8-cineole (15.89%), β-Thujone (6.7%), and camphanone (6.2%) were the main components of AEO. The edible CMC film showed increase in WVP, contact angle, E%, darker color, and yellowness, with decreases in film solubility, MC, and TS after the incorporation of AEO. CMC film with 1.5% of AEO showed the highest a* (greenness) and b* (yellowness) values. The inhibition zones were 9.33, 11.5, and 17.30 mm for Staphylococcus aureus; and 8, 11.50, and 14.33 mm for Escherichia coli at AEO levels of 0.5, 1, and 1.5%, respectively. Conclusion: The overall results of this study showed that CMC films enriched with AEO could be beneficial in food packaging to retard food deterioration.

Modification of the microstructural and physical properties of konjac glucomannan-based films by alkali and sodium carboxymethylcellulose

To apply yuba as an edible film, we evaluated film properties after adding various additives, including plasticizer (glycerol and sorbitol), cross-linking agent (oxidized ferulic acid), emulsifier (sodium pyrophosphate), thicker (sodium carboxymethyl cellulose) and lipid (beeswax), alone or in combination (sodium pyrophosphate and sorbitol; sodium carboxymethyl cellulose and glycerol; and beeswax and glycerol). The addition of beeswax and oxidized ferulic acid enhanced the water resistance of the film, showing a decreased solubility in water and swelling ratio. The results for tensile strength and elongation showed opposite trends, except for sorbitol, sodium pyrophosphate, and sodium carboxymethyl cellulose and glycerol. Tensile strength of sodium carboxymethyl cellulose (9.3MPa) was increased compared to that of yuba without additive (3.5MPa). Elongation was increased in glycerol (132%) compared to that in the control (8%). Water vapor permeability decreased in all samples by 0.7 to 8 times compared to that of the control. X-ray diffraction analysis found that blending additives influenced the crystalline degree and second structure of the film. Atomic force microscopy revealed that the control (37 nm) and sodium carboxymethyl cellulose and glycerol (47 nm) exhibited smooth surface and lower roughness values compared to glycerol (84 nm) and sodium carboxymethyl cellulose and glycerol (87 nm). Our results confirmed that yuba could be used as edible film with a wide range of applications depending on types of additive and purpose of use. The results of the present study revealed that sodium carboxymethyl cellulose and glycerol-added yuba film had exceptional edible film properties, including water resistance, elongation and water vapor permeability based on principal component analysis. © 2018 Society of Chemical Industry.

The growing demand for minimally processed foods with a long shelf life and environmentally friendly materials has forced industry to develop new technologies for food preservation and handling. The use of edible films has emerged as an alternative solution to this problem, and mixtures of carbohydrates and proteins, may be formulated to improve their properties. The objective of this work was to evaluate the effect of protein cross-linking with transglutaminase (TG) of two varieties of quinoa protein isolate (Chenopodium quinoa) [Willd (QW), and Pasankalla (QP)] on the physicochemical and barrier properties of edible films based on chitosan (CT)-quinoa protein. The evaluated properties were water vapor permeability (WVP), solubility, adsorption, roughness determined by atomic force microscopy, and the interactions among the main film components determined by Raman spectroscopy. The results indicated that TG interacted with lysine of QW and QP. CT:QW (1:5, w/w) showed the lowest solubility (14.02 ± 2.17% w/w). WVP varied with the composition of the mixture. The WVP of CT:quinoa protein ranged from 2.85 to 9.95 × 10−11 g cm Pa−1 cm−2 s−1 without TG, whereas adding TG reduced this range to 2.42–4.69 × 10−11 g cm Pa−1 cm−2 s−1. The addition of TG to CT:QP (1:10, w/w) reduced the film surface roughness from 8.0 ± 0.5 nm to 4.4 ± 0.3 nm. According to the sorption isotherm, the addition of TG to CT-QW films improved their stability [monolayer (Xm) = 0.13 ± 0.02 %]. Films with a higher amount of cross-linking showed the highest improvement in the evaluated physical properties, but interactions among proteins that were catalyzed by TG depended on the protein source and profile.

The antimicrobial activities against Escherichia coli O157:H7 as well as the stability of carvacrol, the main constituent of oregano oil, were evaluated during the preparation and storage of apple-based edible films made by two different casting methods, continuous casting and batch casting. Antimicrobial assays of films and high-performance liquid chromatography (HPLC) analysis of film extracts following storage up to 49 days at 5 and 25 degrees C revealed that (a) optimum antimicrobial effects were apparent with carvacrol levels of approximately 1.0% added to the purees prior to film preparation, (b) carvacrol in the films and film weights remained unchanged over the storage period of up to 7 weeks, and (c) casting methods affected carvacrol concentration, bactericidal activity, physicochemical properties, and colors of the apple films. Carvacrol addition to the purees used to prepare the films reduced water vapor and oxygen permeability of apple films. The results indicate that carvacrol has a dual benefit. It can be used to both impart antimicrobial activities and enhance barrier properties of edible films. The cited observations facilitate relating compositional and physicochemical properties of apple puree films containing volatile plant antimicrobials to their use in foods.

Response surface modeling and analysis of barrier and optical properties of maize starch edible films

One method of extending postharvest shelf-life is the use of edible coatings. Such coatings are made of edible materials that are used to enrobe fresh produce, providing a semipermeable barrier to gases and water vapour. Guavas cultivated at Aguascalientes, Mexico were coated with a solution of one of the following polymers: Potato starch, sodium alginate, carragenan, and pectin. The fruit was covered by immersion in the solution at 50°C, then dried at 50°C during 30 minutes. After coating, the maturation process was compared to uncoated fruit. The evaluation of the functional properties of the edible coatings was done by measurement of the barrier properties of edible films to water vapour (gravimetric method) and to aroma compounds (dynamic method). The results showed an increase of the fruit’s shelf-life with at least three days compared to the uncoated fruit, at 25°C and 5070% R.H. The highest efficiency preserving the fruit was obtained with potato starch and pectin based coatings, increasing the preservation of the sensorial characteristics of the fruit (size, yellow colour and aroma) with 15 days. INTRODUCTION The performance of packaging materials depends on their efficiency to reduce transfers between foodstuff and the environment such as the transport of volatile compounds from food to the outer atmosphere or from the surrounding medium to the packaged product (permeation), and the adsorption of volatile compounds at the surface of the packaging (sorption or scalping) (Reineccius, 1991; Benet et al.,1992; Blumenthal, 1997). The technological progress in synthetic packaging materials allows an important and selective reduction of non condensable gas and water vapor exchanges such as that obtained with barrier polymers (Chomon, 1992). Nevertheless, most of plastic packagings have a strong affinity towards hydrophobic volatile compounds, like aroma compounds (Reineccius, 1991; Leufven and Stollman, 1992; Miller and Krochta, 1997). Moreover, plastic materials can not be used to protect any kind of foods: for example, to separate two different parts in a heterogeneous product such as a pie or a pizza (Kamper and Fennema, 1985; Kester and Fennema, 1989). Therefore, the combination of edible and plastic materials has been proposed to improve their functional properties. Many storage techniques have been developed to extend the useful marketing distances and holding periods for fresh horticultural commodities after harvest. Various authorities have estimated that 25 to 80% of harvest fresh fruits are lost due to spoilage. This results in much economic waste in developed countries and more devasting consequences in countries such as Mexico, with economic and agricultural problems in the last 20 years. One method of extending postharvest shelf-life is the use of edible coatings. Such coatings are made of edible materials that are used to enrobe fresh Proc. Postharvest Unltd Eds. B.E. Verlinden et al. Acta Hort. 599, ISHS 2003 590 produce, providing a semipermeable barrier to gases and water vapour. To understand the effect of edible coatings on harvested fruits, a background knowledge of postharvest fruit physiology and storage techniques is necessary (Baldwin, 1994). The objectives of this work were to apply edible coatings based on potato starch, pectin, carragenan or sodium alginate on mexican guava fruit to increase their shelf-life and to better understand the effect of coatings on maturation and respiration of fruits. MATERIALS AND METHODS Preparation of Coatings Guavas cultivated at Aguascalientes, Mexico were coated with a solution of one of the following polymers: Potato starch, sodium alginate, carragenan, and pectin. The polymer content in the solution was between 5 and 10%. Glycerol was used as a plasticizer as commonly signalled in literature (between 10 and 30%). The polymer and plasticizer content in the solution was determined by factorial statistics method. The fruit was covered by immersion in the solution at 50°C, then dried at 50°C during 30 minutes. After coating, the maturation process was compared to uncoated fruit. The evaluation of the functional properties of the edible coatings was done by measurement of the barrier properties of edible films to water vapour (gravimetric method) and to aroma compounds (dynamic method) (Felder, 1978). Water Vapor Permeability Measurement The water vapour transfer rates (WVTR) were determined with the gravimetric method described in the ASTM E96-80 standard used for the determination of water vapour transfer rate through sheet packaging materials and modified by Debeaufort et al. (1993) Films were fixed between two Teflon rings on the top of a glass cell containing a saturated salt solution of potassium chloride (Merck, Germany) of which the water activity is 0.84 at 25°C. Test cells were placed onto the balance plate in a ventilated cupboard which temperature and relative humidity were fixed respectively at 25°C and 22% using potassium acetate saturated solution (Merck, Germany). Permeation cells were continuously weighed and recorded by a computer. When the relationship between the weight loss and time was linear, the slope of the plot was used to calculate the water vapor transfer rate (WVTR) and water vapor permeability (WVP). All the films were equilibrated over silica gel at 5-6% RH and 25°C for 15 days before permeability determinations. Vapor Permeability Measurement A dynamic measurement method of aroma vapor fluxes through films or membranes was used. The apparatus has been described by Debeaufort and Voilley (1994). The permeation cell was composed of two chambers divided by the film to be studied. The film area exposed to transfer was 15.9 cm. The two chambers were continuously swept by a 30 mL.min helium flow. The aroma concentrations in the vapor phase on the upper side of the cell were obtained by mixing two flows : one containing the volatile compound and the other dry helium. Flows containing vapors were obtained from bubbling dry helium through pure compounds. Organic volatile were analyzed with a flame ionizing detector (FID). Samples were weighed before and after permeation measurements to determine the amount, Q, of volatile sorbed within the films, expressed as micrograms of volatile per milliliter of dry film (μg.mLd.f.). The gravimetric method used to determine Q was compared for some samples to values obtained by the method described further in this paper, and they were considered as enough accurate. Films were equilibrated at 0% relative humidity at 25°C before permeability determinations. Permeation measurements were carried out at 25°C. Vapor concentration differentials were between 0 and 2.5 μg. mL He for 2-nonanone, between 0 and 7.0 μg. mL He for 2-octanone and between 0 and 23 μg. mL He for 2-heptanone (Quezada Gallo et al., 1998). The highest concentration of aroma in the vapor phase (saturation) was obtained by bubbling a carrier gas through pure aroma at 25°C and atmospheric

Control of moisture transfer inside composite food products or between food and its environment remains today a major challenge in food preservation. A wide rage of film-forming compounds is now available and facilitates tailoring moisture barriers with optimized functional properties. Despite these huge potentials, a realistic assessment of the film or coating efficacy is still critical. Due to nonlinear water sorption isotherms, water-dependent diffusivities, and variations of physical state, modelling transport phenomena through edible barriers is complex. Water vapor permeability can hardly be considered as an inherent property of films and only gives a relative indication of the barrier efficacy. The formal or mechanistic models reported in literature that describe the influence of testing conditions on the barrier properties of edible films are reviewed and discussed. Most of these models have been validated on a narrow range of conditions. Conversely, few original predictive models based on Fick's Second Law have been developed to assess shelf-life extension of food products including barriers. These models, assuming complex and realistic hypothesis, have been validated in various model foods. The development of nondestructive methods of moisture content measurement should speed up model validation and allow a better comprehension of moisture transfer through edible films.