Functionalized Agricultural Packaging Preedawan Duangchan a, Rathanawan Magaraphan* a a The Petroleum and Petrochemical College, Chulalongkorn University Keywords : Active Packaging, Carboxymethyl cellulose, vanilla, control release ABSTRACT Durian is the aroma overpowering and revolting. The persistence of its odour, So searching for the use of environmentally friendly products and new applications, The production of Active packaging and more specifically control aroma and antimicrobial packaging films are innovative concepts in food packaging. The influence of water vapour conditions on mass transport and barrier properties of CMC based films and coatings were studied in relation to structural properties. Water contact angles, material swelling, barrier properties (PO 2, WVTR) and aroma diffusion coefficients were determined. The solvent nature and the presence of essential oils (vanilla and rosemary) influenced the surface and structural properties and then the barrier performance of activated CMC films. Increasing RH led to a significant increase in material swelling. The plasticization effect of water was more pronounced at high humid environment, while at low RH the matrix plasticization was induced by essential oils. The essential oils release from the CMC matrix was strongly influenced by RH. A temperature increase from 25 to 40 C also had an impact on essential oil diffusivity but to a lesser extent than RH. INTRODUCTION Thailand is famous for foods including fruits and vegetables with excellent taste. There are many foods with strong smell e.g. marinated vegetables and fishes. Durian is known as king of fruits also having the aroma overpowering and revolting. The smell evokes reactions from deep appreciation to intense disgust The persistence of infavored odour, which may linger for several days, has led to the banishment from certain hotels and public transportation. With the new awareness in searching for the use of environmentally friendly products and new applications, a novel kind of active packaging referred to as interactive or Smart packaging, is designed based on bio-plastics (polylactic acid, PLA and carboxymethyl cellulose, CMC) with ability to be stimulated by the food inside and responded by controlling or alleviating the smell. The aim of this study was to investigate the influence of RH on the surface and thermal properties of bio-based polymer self standing films and coatings applied onto PLA films. For this purpose we used CMC and essential oils as models of biopolymer matrices and active compounds with an antimicrobial potential. The effect of incorporated essential oils on the structure changes was studied. Water vapour, oxygen and carbon dioxide permeability has also been studied in order to monitor the film behaviour according to the temperature and RH and studied aroma diffusion coefficients Petrochemical and Materials Technology Tuesday May 23, 2017, Pathumwan Princess Hotel, Bangkok, Thailand Page 1
EXPERIMENTAL A. Materials Lactide monomer (LA) (99.5% purity) was obtained from Shenzhen Bright China Industrial Co., Ltd. Poly(vinyl alcohol) (PVOH, PVA, or PVAl) has the idealized formula [CH 2 CH(OH)] n. Commercial Carboxymethyl Cellulose, A food-grade ;Vanilla Essential Oil and Rosemary Essential Oil. All materials were used without further purification. B. Film preparation 1.) Self standing CMC films A CMC solution was prepared by dissolving the CMC in a distilled water, to obtain 0.5, 1, 1.5, 2% (w/v) film forming solutions, the solution was homogenized at 5,000 rpm for 30 minute temperature at 70 C. To achieve a complete dispersion of the CMC. Adding polyvinyl alcohol 1% (w/w) and Polysorbate 80 0.5% (w/v) into CMC solution,was homogenized. After that, Vanilla ( 0.5%, 0.75%, 1% w/v) mixing with CMC solution was homogenized, to obtain film forming solutions with an incorporated aroma compound. In order to obtain films, The mixture was gradually dried in a desiccator at 40 C and 30% RH to remove excess water. 2.) CMC coated polylactid acid film The carboxymethyl cellulose solution with/or without rosemary or vanilla was prepared as described in Section 1.) The coating was using Compression molding. After laminating, the films were stored in a desiccator before measurements at 25 C and 30% RH. C. Film characterisation 1.) Contact angle and Wettability The contact angle, surface hydrophobicity and wettability of films were measured by the sessile drop method, in which a drop-let of the tested liquid was placed on a horizontal film surface 2.) Water vapour transmission rate (WVTR) The WVTR of films was determined gravimetrically using a modified ASTM E 96 standard method, using the RH of 90 2 % and the temperature of 38 ± 1 C. Prior to the WVTR measurements, all the film samples were equilibrated at 38 ± 1 C and 90% RH for 24 h. The conditions under which the measurement is made has a considerable influence on the result. Both the temperature of and humidity gradient across the sample need to be measured, controlled and recorded with the result WVTR (g.m 2 /day) 3.) Oxygen Transmission Rate The OTR of films was determined gravimetrically using a modified ASTM D 3985 standard method, the measurement of the amount of oxygen gas that passes through a material over a given period of time. OTR is measured in either cc/m 2 /24 hours 4.) Differential scanning calorimetry (DSC) DSC (Perkin Elmer) will be used to determined Heat Capacity of samples. The 4-8 mg of samples was put into aluminum pan. The samples were heated from 25 to 220 o C at heating rate 10 o C/min. Petrochemical and Materials Technology Tuesday May 23, 2017, Pathumwan Princess Hotel, Bangkok, Thailand Page 2
RESULTS AND DISCUSSION A. Surface hydrophobicity 1.) Contact Angle First of all, material wettability was tested in order to better understand how % of CMC influences the surface properties of CMC based films and coatings. From Fig. 3 and Fig. 4 ; three types of behaviour can be observed. Changes in behaviour were depended on the polymer nature. Indeed, the water cannot be absorbed on the PLA. On the coated PLA the water droplet profile began to change immediately upon deposition onto the CMC-coated surface (Fig. 3). Close values of swelling (63.1 ± 1.11, 13.8 ± 1.29, 21.1% ± 1.87 for PLA and coated PLA, respectively), explain why no significant changes were observed in the contact angle values of PLA and coated PLA. Still, the presence of the thin CMC layer caused the swelling of the coated side. Contrarily, films based on CMC have non-linear behaviour where changes such as solvatation, hydration and/or swelling occurred Figure 1 : Shape and volume changes of water drop deposit on different carboxymethyl cellulose 0.5 % w/w/polyvinyl alcohol based films (a ; t = 0s), carboxymethyl cellulose 1 %w/w/polyvinyl alcohol based films (b ; t = 0s), carboxymethyl cellulose 1.5 %w/w /polyvinyl alcohol (c ; t = 0s), carboxymethyl cellulose 2 %w/w /polyvinyl alcohol based films (d ; t = 0s) ; * coated Polylactic acid B.Barrier properties 2.) Water vapour transmission rate Barrier properties are vary important in packaging applications. Because of the potential for fully green cellulose composites in packaging field, WVTR of all CMC* coated PLA films are significantly increased as compared to pure PLA. The amount of carboxymethyl cellulose is significant effect on WVTR of carboxymethyl cellulose self-standing film. The WVTR values for all CMC films increased, probably could be explained by higher hydrophilic groups of CMC after substitued by carboxymethyl groups on cellulose structure. Petrochemical and Materials Technology Tuesday May 23, 2017, Pathumwan Princess Hotel, Bangkok, Thailand Page 3
Figure 2 : At 38 C and %90RH of CMC* self-standing films compared to CMC* self-standing coated PLA and PLA films. Figure 3 : Oxygen transmission rate (OTR) at 23 C and 0%RH of CMC* self-standing coated PLA films. 3.) Oxygen transmission rate Second studies about OTR for comfirm ability of CMC bio based film In this graph show that PLA giving high OTR but the oxygen transmission rate values of the samples coated with polylactic acid were reduce largely to very low OTR. the permeability of gas decrease with the incorporation of percentage content of carboxymethyl cellulose While the film from 2% carboxymethyl cellulose coated PLA showed the lowest value of OTR. It good properties for packaging because it cannot occer lipid peroxidation (oxidative degradation of lipids) CMC 0.5 % CMC 1 % CMC 1.5 % CMC 2 % Figure 3 : The carboxymethyl cellulose* self-standing films coated PLA films. Figure 4 : durian testing during 18 day at 60%RH and (a) temp. 25 C (b) temp. 40 C C. Optical property The apparently anomalous variations of the shape constants of carboxymethyl cellulose with Poly(vinyl alcohol) coated polylactic acid films with different the amount of carboxymethyl cellulose can be attributed to the nature of such films. Accordingly, it turns out that the shape property play an important role in the packaging film. it can be seen that shape of carboxymethyl cellulose self-standing films with polyvinyl alcohol coated polylactic acid. 0.5% carboxymethyl cellulose cannot hold a temporary thickness of film is lowest (113 m) Petrochemical and Materials Technology Tuesday May 23, 2017, Pathumwan Princess Hotel, Bangkok, Thailand Page 4
while 2% carboxymethyl cellulose have high thickness (120 m) it can still hold a temporary shape properly use for packaging film D. Active packaging Testing Figure 5 : Kinetic of Vanilla release from carboxymethyl cellulose* self-standing coated PLA films during 18 days influenced by both relative humidity and temperature 25 C (a) and 40 C (b). The release mechanisms are quite important from the application point of view. When estimating the shelf life of the active packaging film. we want to avoid active compound loss. On the contrary, as soon as the packaging is put in the atmosphere of a real fresh food product, where temperature in environment and thus RH in the packaging is high, accumulated water vapour would favour the release of vanilla and thus induce the adsorption on the food surface.after storage 18 day it can found that shape of durian changed shown in Figure 4 suggest that when storage over time durian was dry and it have odour of durian smaller than first day, it can confirm that vanilla-releasable bio-plastic film (2 wt% CMC/PLA with specified loading of vanilla) can absorb water ( self anti-fog ) following from contact angle and mitigate odour of durian following evaluation CONCLUSIONS 2% of CMC* content showed great potential to be used as self-standing film. CMC* coated PLA films showed great potential to be used as active aroma support matrices. These matrices can provide activity to food packaging films, by humidity and temperature induced release mechanisms The vanilla release was strongly influenced by temperature and humidity ACKNOWLEDGEMENTS The author is grateful thanks for the scholarship and funding of the thesis work provided by the Petroleum and Petrochemical College; Petrochemical and Materials Technology Tuesday May 23, 2017, Pathumwan Princess Hotel, Bangkok, Thailand Page 5
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