Oriented Polypropylene Research Articles

Is the use of correct terms and definitions important in creation of new materials?

and widely applied term is a case in composite community, where the thermodynamic term ‘phase’ is used instead of the term ‘component’. Obviously, the misuse of the term ‘phase’ is a remnant from the time when the colloid chemistry was formulated (second half of 19th century, i.e. long before the polymer science was defined). The confusion of this misuse can be easily demonstrated by poly(vinylidene fluoride) (PVDF) exhibiting five crystalline polymorphic modifications (phases!) and one amorphous phase but PVDF is still a one-component system. While this example does not have a direct effect on the creation of new materials, the next one, the definition of the relatively new type of polymer composites, the single polymer composites (SPCs), does. SPCs have also been called: one polymer composites (R. Porter), homocomposites, self-reinforced composites, one-phase composites, homogeneous composites, or all-polymer composites. The concept of SPCs has been formulated by R. Porter some 40 years ago (DOI: 10.1007/BF00554928) as attempt to solve the basic problem in polymer science and technology, namely, the low adhesion quality between matrix and reinforcement due to their different chemical composition. The approach is quite simple – the matrix and the reinforcement have to be of the same polymer, i.e. to be chemically identical. The idea attracted the attention of academia and industry during the last decade when patents were registered and products were commercialized; nanofibrillar SPCs with superior mechanical properties were also created (DOI: 10.1002/mame.201200226). What is more, similar products were prepared and called also SPCs (DOIs: 10.1007/s10853-009-3792-1, and 10.1016/j.compscitech.2013.12.006) using highly oriented poly propylene (PP) (as reinforcement) and the random copolymer of PP (usually with polyethylene) as a matrix thus neglecting the basic requirement (R. Porter) for identical chemical composition of matrix and reinforcement. Strictly speaking, such composites belong to the category of polymer–polymer composites. The same holds for thermoplastic copolyesters reinforced with ‘homo’-poly(ethylene terephthalate). The argument that the two chemically different components belong to the same polymer family (DOI: 10.1016/j.compscitech.2013.12.006) could hardly be seriously considered – it only smears the boundary between the two types of composites, the polymer-polymer ones and the SPCs and makes the clear definition of single polymer composites hardly possible affecting in this way negatively their further development! In order to make use of the unique properties of SPCs we should not forget that they could be multi-phase but always remain one-component systems!

연신 폴리프로필렌 필름으로 진공 포장된 팽이버섯(Flammulina velutipes)의 저장성 향상

The shelf-life of fresh mushrooms is notably limited because their browning, texture change, and decay are too fast after immediately harvest. Especially, the best management for extending golden needle mushroom’s shelf-life is modified atmosphere packaging under pressure vacuum at cold storage. In this study, three types of films, 20 μm polyethylene+polypropylene (PE+PP), oriented polypropylene (OPP), and low density polyethylene (LDPE) were tested to extend the shelf-life of golden needle mushrooms. Mushrooms were packed under pressure vacuum and stored at 10 °C for 2 weeks. The golden mushrooms in LDPE film as a commercial packaging, were highly perishable and immediately proceed deterioration as browning, elongation, fluctuation of respiratory quotient (RQ) and softening within 7 days after packaging. On the other hand, the mushrooms in OPP and PE+PP film shown that shelf-life were extend to 14 days from 7 days, causing delay breakup of vacuum and maintenance of color, length, and RQ during storage. The breakup of vacuum in PE+PP film was faster few days than OPP film packaging. This present study indicated that the golden needle mushrooms by OPP packaging under pressure vacuum treatment might be extended the shelf-life until approximately 14 days during cold storage.

Electric Field and Temperature Dependence of Electrical Conductivity in Biaxially Oriented Polypropylene Films

In pulsed power systems, metallized film capacitors facilitate the operation of the film with a relatively small margin to its dc breakdown strength. Electrical conduction in metallized biaxially oriented polypropylene (BOPP) film may result in the leakage in high energy density capacitors and thus the reduction of the energy efficiency. This paper investigates the mechanism of the electric field and temperature dependence of electrical conduction in the BOPP film capacitor. A proposed model for the electrical conductivity takes into consideration both the Poole-Frenkel effect and field-enhanced carrier mobility. Experiments are performed to measure the electrical conductivity of the BOPP film at different electric fields and temperatures.

Effect of Modified Atmosphere Packaging on Postharvest Quality of Kohlrabi

Abstract: The effect of modified atmosphere packaging (MAP) on kohlrabi (Brassica olerace L. gongulodes group)’s quality and antioxidant molecule during storage was examined to determine the optimal film package for maintaining freshness. To extend shelf life, MAP was tested using PE 50 μm and oriented polypropylene (OPP) films with oxygen transmission rate (OTR) at 3,000, 10,000, 15,000 mL/m 2 /day/atm. The OPP film packaging with modified oxygen transmission rate showed a delay in a weight loss and extended storage period. The package with OTR 3000 attained the desired gas composition of O 2 3.2-6.7 kPa and CO 2 13.1-19.8 kPa, in storage at room temperature. Kohlrabi stored in this package showed the lowest weight loss and the highest visual quality. Deterioration and off-odor were developed more rapidly in PE 50 μm towards the end of the storage at room temperature. However, there are no differences among OTR films in visual quality and off-odor until 60 days at cold storage. Vitamin C content of kohlrabi was reduced rapidly in OTR 15000 with high transmission rate and showed less loss in PE 50 μm and OTR 3000 in both room temperatures and cold storage. Results revealed that an OPP film with OTR 3000 extended the shelf life of kohlrabi in storage with maintained quality and vitamin C.Additional key words:

Effect of different new packaging materials on biscuit quality during accelerated storage.

The effect of innovative multilayer packaging materials versus a standard one on biscuit quality was studied during accelerated storage at 25, 35, 45 °C and 50% relative humidity for 92 days. Three different packaging materials were used: metalized orientated polypropylene (OPP)/paper (control); metalized poly-lactic acid (PLA)/paper; metalized OPP with ethylene vinyl acetate pro-oxidant additive (EVA-POA)/paper. EVA-POA additive is used to make the plastic layer biodegradable. Various quality sample parameters (moisture, water activity (aw ), texture, peroxide value (PV), hexanal) were analysed during storage. Rate constants (k) and activation energies (Ea ) of hydration reactions and hexanal formation were calculated. No remarkable differences in the evolution of primary and secondary lipid oxidation were observed among differently packed biscuits during storage. All samples maintained PV levels between 4 and 14 meq O2 kg(-1) oil. The product in flexible packaging with PLA reached the highest moisture and aw levels, but they did not significantly and adversely affect the other quality characteristics. The obtained results demonstrate that the new tested packaging materials were suitable for commercial biscuit storage, having similar performance and preservation effects on the overall product quality to those of the standard one. Furthermore, these results could make a contribution to the food industry, encouraging the use of packaging materials with a negligible environmental impact as an alternative to petroleum-based ones.

포장 필름의 종류에 따른 저장 중 콩나물의 품질특성

Correct packaging enables processors to pack fresh produce and extend its shelf life. This study was carried out to investigate the effect of different packaging materials on the weight loss, pH, O2, CO2 and sensory characteristics of soybean sprouts during their storage at 5°C for seven days. Soybean sprouts (320±20 g) were packaged with oriented polypropylene (OPP) and cast polypropylene (CPP) films, respectively. The O2 transmission rate of the packaging materials was set to have a control of 10,000 cc/m.day.atm, and an OP15 and CP15 with 15,000 cc/m.day.atm through a pre-screening test. The average weight loss of the soybean sprouts during their storage was less than 10%, and that of the soybean sprouts with a CPP film was higher than that of the OPP film. The pH of the soybean sprouts increased during their storage regardless of their packaging materials; but compared to the pH of the soybean sprouts packaged with OPP, those packaged with CPP were higher. The CO2 content of the packaging increased with a decrease in the O2 content. The ratio of CO2 to O2 in the soybean sprouts with the OPP film was 3.5 times higher than in the soybean sprouts with the CPP film. The results of the overall sensory test showed that the marketability of the soybean sprouts packaged with OPP film and stored at 5°C seemed to have been maintained effectively for six days (at a 15,000 cc/m.day.atm O2 transmission rate). When the correlation coefficients of the control, OP15 and CP15 were analyzed, the highest correlation was shown between a control and OP15 (0.986; p<0.01).

Master packaging system for sweet persimmon applicable to produce supply chains

Modified-atmosphere-packaged sweet persimmons experience significant quality loss due to temperature fluctuations in the food supply chain, which cause an imbalance between respiration and package gas permeation. This imbalance results in the package atmosphere deviating from the tolerable range. In this study, a master packaging system was designed to maintain a suitable modified atmosphere around the fruit during pre-sale chilled storage and during retail display to preserve freshness. A 50-μm-thick low-density polyethylene (LDPE) outer liner bag containing 46 individual fruit packages (30-μm-thick oriented polypropylene (OPP) film bag with a micro-perforation of about 60μm) was placed within a corrugated paperboard box. Master packaging systems with and without the absorbent sachets were stored for 122d at 0°C and were periodically opened to remove and store the individual primary package units for 10d at 10°C to simulate retail display conditions. The master packaging systems were compared to 10-kg bulk packages containing individual fruit inside a 50-μm-thick LDPE film bag in terms of package atmosphere and fruit quality. Individual fruit packages consisting only of 30-μm-thick, micro-perforated OPP films without an outer liner bag were subjected to the pre-sale 0°C storage for comparison. The master packaging systems maintained an atmosphere with O2 concentrations of 0.8–3.9% and CO2 concentrations of 8.4–15.0% around the fruit during storage at 0°C and during display at 10°C. The high-temperature retail display, after chilled storage at 0°C, resulted in a drastic decline in quality, even with some alleviation offered by the master packaging system. The overall benefits were reduced weight loss, reduced physiological deterioration (e.g., flesh softening and surface blackening) and better retention of firmness and ascorbic acid during the chilled storage and/or the display conditions.

전처리 및 포장방법이 냉풍감압건조 복숭아의 품질에 미치는 영향

This study was conducted to investigate the effects of pretreatment and different packaging methods on the physicochemical properties of cold vacuum-dried peaches. All the dried peach samples were stored such as gas substitution, vacuum and passive packaged with polyethylene (PE) film and oriented polypropylene (OPP)/aluminum (Al)/PE film at for 50 days. The weight change, pH, soluble solids content, titratable acidity, soluble solid-acid ratio (SS/TA), delta E, browning degree and phenolic compounds were analyzed. The weight change and pH were lower in the 0.1% vitamin C-treated group and were significantly lowest in the vacuum-treated OPP/AL/PE. The soluble solids content and the SS/TA were higher in the non-treated groups than in the vitamin C-treated groups. According to the packaging methods, the values were higher in the vacuum, gas and passive package, in that order. In addition, the browning degree and the delta E value were lower in the pretreated groups and significantly lowest in the vacuum-treated OPP/AL/PE with 0.1% vitamin C group. The phenolic compounds were high for the pretreated groups, according to the packaging methods (vacuum > gas> passive), and the OPP/AL/PE was significantly higher than the PE. These results suggest that different packaging materials and pretreatment methods affected the quality of the dried peaches, and the vacuum-OPP/AL/PE film packaging group showed a high quality.

Optimized PLA-based EMAP systems for horticultural produce designed to regulate the targeted in-package atmosphere

An innovative biodegradable bio-based film packaging system has been designed to achieve equilibrium modified atmosphere packaging (EMAP) of high value fresh horticultural produce through tuning the packaging barrier properties combining laser micro-perforation, breathable membrane technologies and materials. The tested commodities were cherry tomatoes and peaches. Laser micro-perforated 30μm polylactic acid (PLA) film was used as the main bio-based packaging material. Key parameters of the novel bio-based EMAP system for the selected horticultural produce were optimized in terms of performance and cost reduction. Laboratory experiments were employed in order to validate the optimal design of the innovative EMA package. Results from lab experiments show improved efficiency of the optimized PLA based EMAP system in prolonging the shelf-life time of horticultural commodities as compared to non-packed commodities and commodities packed with conventional oriented polypropylene (OPP) film. The exposure of the PLA film to the EMA packed fresh produce conditions during the shelf-life period has negligible effect on the mechanical, physical and chemical properties of the film.

Effect of Low-Pressure Nitrogen DC Plasma Treatment on the Surface Properties of Biaxially Oriented Polypropylene, Poly (Methyl Methacrylate) and Polyvinyl Chloride Films

In this study, commercial biaxially oriented polypropylene (BOPP), polyvinyl chloride (PVC) and poly (methyl methacrylate) (PMMA) films were treated with nitrogen plasma over different exposure times in a Pyrex tube surrounded by a DC variable magnetic field. The chemical changes that appeared on the surface of the samples were investigated using Fourier transform infrared (FT-IR) spectroscopy and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy after treatment for 2 min, 4 min and 6 min in a nitrogen plasma chamber. Effects of the plasma treatment on the surface topographies and contact angles of the untreated and plasma treated films were also analyzed by atomic force microscopy (AFM) and a contact angle measuring system. The results show that the plasma treated films become more hydrophilic with an enhanced wettability due to the formation of some new polar groups on the surface of the treated films. Moreover, at higher exposure times, the total surface energy in all treated films increased while a reduction in contact angle occurred. The behavior of surface roughness in each sample was completely different at higher exposure times.

포장방법이 강정의 저장 중 품질특성에 미치는 영향

본 연구에서는 강정의 포장방법 및 포장재질이 강정의 저장 중 품질특성에 미치는 영향을 조사하기 위해서 포장방법별로 개별포장, 대형포장 및 봉지포장의 3가지 방법과 8개의 포장재질을 사용하였다. 강정 포장은 (1) IP: OPP/PE+종이, (2) LP1: OPP/PE+종이, (3) LP2: OPP/PE+관, (4) LP3: OPP/PE+플라스틱, (5) BP1: OPP/PE, (6) BP2: OPP/DL/CPP, (7) BP3: PET/PE/CPP, (8) BP4: OPP/PVDC/PE/CPP로 구분하였다. 강정의 저장초기 지방산 조성은 linoleic acid(54.2%), oleic acid(24.1%), palmitic acid (11.2%) linoleic acid(6.0%) and stearic aicd(3.8%)이었으며, 저장중 수분함량, 수분활성도, 경도, 산가, 과산화물가를 측정하였다. 저장 중 수분함량의 변화가 늦게 나타난 시료는 LP2, BP4 > IP > LP3, BP1, BP2 > LP1 > BP3 순이었다. 수분활성도는 큰 차이를 보이지 않았으며, 경도는 IP, BP3 및 BP4는 저장 60일에 증가의 폭이 가장 크게 나타났다. 산가는 IP, LP1, LP2, LP3, BP1 및 BP2 경우 저장 40일에 기준치인 2.0 mg KOH/g 이하이었으며, 과산화물가는 IP, LP1, LP2 및 BP1의 경우 기준치인 40.0 meq/kg 미만이 20일째인 것으로 나타났다. 결론적으로 포장재질별로는 LP2와 BP1이 저장성이 우수하였으며 포장방법별로는 대형포장 >봉지포장 >개별포장 순으로 나타났다. This study was conducted to improve the packaging technology used for Gangjung and the product's quality characteristics during storage. Packaging materials consisting of (1) IP: OPP (oriented polypropylene)/PE (polyethylene) + Paper, (2) LP1: OPP/PE + Paper, (3) LP2: OPP/PE + Can, (4) LP3: OPP/PE + Plastic, (5) BP1: OPP/PE, (6) BP2: OPP/DL/CPP (cast polypropylene), (7) BP3: PET/PE/CPP, and (8) BP4: OPP/PVDC (polyvinylidene chloride)/PE/CPP were used. The major fatty acids including 54.2% linoleic acid, 24.1% oleic acid, 11.2% palmitic acid and 6.0% linoleic acid were assessed. The packages effective in maintaining moisture were in the order of LP2, BP4 > IP > LP3, BP1, BP2 > LP1 > BP3. There were no significant differences in water content and the products in IP, BP3, and BP showed the highest level in the increase in hardness on day 60 of storage. Acid values of IP, LP1, LP2, LP3, BP1, and BP2 were maintained at <2.0 during 40 days of storage. IP, LP1, LP2 and BP1.

어린잎 채소 다채의 포장방법이 품질에 미치는 영향

The effect of the packing methods for enhancing the shelf life and improving the postharvest quality of the Chinese cabbage baby leaf vegetable was studied during storage. Fresh baby leaf vegetables were packed in four commercial packaging types: (1) a non-perforated bag with a 0.03-mm oriented polypropylene (OPP) film; (2) a perforated bag with 1.0-mm-diameter holes on an OPP film; (3) a 0.40-mm polyethylene terephthalate (PET) container with a hinged lid; and (4) an expanded polystyrene (EPS) tray wrapped with a 0.02-mm polyvinyl chloride (PVC) film. The quality parameters, such as the weight loss, moisture content change, color difference, and appearance of the baby leaf vegetables were investigated. The baby leaf vegetables in the PET container and in the non-perforated OPP film bag showed relatively low weight loss, high moisture content, and good external appearance compared to those in the EPS tray and in the perforated OPP film bag during limited storage periods, at . The PET container also protected the baby leaf vegetables from physical damage. The study results will enable the selection of a better packaging system for extending the freshness and increasing the market ability of baby leaf vegetables.

Improvement of oxygen barrier of oriented polypropylene films coated by gravure ink‐containing nanoclays

AbstractThe feasibility of a gravure ink‐containing nanoclays as an alternative oxygen (O2) barrier material to oriented polypropylene (OPP) film was investigated. The gravure ink was effectively dispersed through the clay using an ultrasonic homogenizer. Barrier properties of OPP films coated by the gravure ink‐containing nanoclays were evaluated with respect to dispersion time, clay content, and different types of nanoclays (Cloisite Na+, Cloisite 25A, and Cloisite 30B). Barrier and morphology properties of the OPP films were tested by measuring selected film properties such as O2 transmission rate (OTR), and water vapor transmission rate, and by field emission scanning electron microscopy, X‐ray diffraction (XRD), and transmission electron microscopy (TEM). OTR of control OPP film coated solely with gravure ink was 1653 cm3 m−2 day, while use of OPP films coated by the three different types of gravure ink‐containing nanoclays (nanoclay content: 1% w/w) reduced OTR by 12–37%. OTR values measured using the gravure ink‐containing modified montmorillonite (Cloisite 25A and Cloisite 30B) were markedly lower than measured by pristine gravure ink‐containing unmodified montmorillonite (Cloisite Na+). On the other hand, no remarkable differences were evident in the water vapor barrier performance of control OPP film and gravure ink‐containing nanoclay‐coated OPP film. As nanoclay content and dispersion time increased, OTR values of the OPP films coated by gravure ink‐containing nanoclays decreased. And the TEM and XRD observation indicated that intercalated and exfoliated types were generated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Structural Transformations during the Low-Temperature Annealing of Biaxially Oriented Polypropylene Film

By differential scanning calorimetry, and from the buildup of longitudinal shrinkage, a study was made of the kinetics of structural relaxation during the low-temperature annealing of biaxially oriented polypropylene film. It was established that the first, rapid stage of structural relaxation normally occurs in the process of product manufacture. The second, slow stage, comprising the process of secondary crystallisation, occurs in the course of storage and service. The kinetic parameters of secondary crystallisation and accompanying longitudinal shrinkage that make it possible to predict the kinetics of these processes in a wide range of temperatures and observation times were determined.

Analysis of the effect of perforation on the permeability of biodegradable non-barrier films

Perforated plastic films are used in Equilibrium Modified Atmosphere Packaging (EMAP) of fresh produce such as fruits and vegetables. The most common material used in such applications is the oriented polypropylene (OPP), which has low permeability with respect to relevant gases, namely water vapor (WV), CO2, and O2. Therefore, the synthesis of the in-package atmosphere is regulated only by the size and number of perforated holes. The replacement of the OPP films with biodegradable ones made of polylactic acid (PLA) or starch based polymers for environmental reasons results into difficulties with respect to designing the EMAP system, since these films are more permeable to the relevant gases and in particular to WV. As a result, the effect of micro-perforation is influenced by the permeability of the film. In the present work, the dependence of the gas flux through perforation on the permeability of the film for the same gas was investigated by experimental and numerical methods. It was shown that the effect of perforation decreases as the permeability of the film increases. The diffusive gas flux through perforation becomes independent of the film permeability, if it is about 100 times smaller than the diffusivity of the studied gas in air.

Plasma Surface Functionalization of Biaxially Oriented Polypropylene Films with Trimethyl Borate

The radiofrequency plasma (13.56 MHz) was employed to polymerize trimethyl borate (TMB) monomer/N2 gas mixture on the surface of biaxially oriented polypropylene (BOPP) films. Plasma polymer coated polypropylene films were examined by flame retardancy test (limiting oxygen index, LOI). The highest LOI value calculated for the untreated BOPP sample was 18.4 (v/v O2%) and 24.2 (v/v O2%) for the 55 W 30 minutes treated sample. The plasma polymers were characterized by FTIR spectroscopy and AFM. According to the FTIR results, the -OH, B-CH3, B-O, and BH2 functional groups were detected. It was found that the highest surface roughness belonged to 40 W 30 min treated BOPP sample which was calculated as 9.78 nm (10 μm × 10 μm). Moreover, the wettability of the modified BOPP film surfaces was characterized via contact angle measurements. The water contact angle values have decreased from 109.6? to the lowest value of 68.2? after the plasma treatment. The results showed that TMB/N2 plasma modification could be used as an alternative method for the enhancement of flame retardancy and hydrophilicity of BOPP film.

Classification of OPP adhesive tapes according to pyrogram of adhesives

Pressure sensitive adhesives (PSAs) of colorless and transparent oriented polypropylene (OPP) adhesive tapes were analyzed by pyrolysis/gas chromatography/mass spectrometry (Py/GC/MS). The PSAs were acrylic and rubber-based PSAs and the tapes were classified according to total ion current (TIC) chromatograms of the PSAs. The main pyrolyzates of the acrylic PSAs were decomposition products of monomers, monomers, dimmers and trimers. Those of the rubber-based PSAs were the monomers of elastomers, and subtle peaks observed were the pyrolyzates of tackifiers and volatile additives in the TIC chromatograms. Small differences were observed among the classifications of the acrylic PSAs by Py/GC/MS, attenuated total reflection Fourier transform infrared (ATR FT-IR) and Matrix-assisted laser desorption/ionization mass spectrometry (MALDI/MS). The classification of the rubber-based PSAs by Py/GC/MS and that by ATR FT-IR were the same, and a slight difference was observed between those by Py/GC/MS and MALDI MS.

AN EMPIRICAL APPROACH FOR ASSESSMENT OF SAFE STORAGE PERIOD FOR BUTTON MUSHROOM (AGARICUS BISPORUS) BASED UPON COLOR CHANGES UNDER MODIFIED ATMOSPHERE PACKAGING

ABSTRACT White button mushroom accounts for 35–45% of the total mushroom produced in the world. Modified atmosphere packaging or MAP is a technology that, along with low temperature storage, helps in extending the shelf life and maintenance of quality of the produce packaged in polymeric films. The present study mathematically modeled the various transport processes associated with the mushroom under MAP at 15C and 75% relative humidity (RH) using the enzyme kinetics approach. Low density polyethylene (LDPE), polypropylene (PP) and oriented polypropylene (OPP) films were used to pack the mushroom. Numerical solutions to the transient state equations were programed in a computer programing language to predict the in-pack gaseous partial pressures at any instant of time. The model was experimentally validated, and a simple qualitative tool based upon optimum whiteness of mushroom was developed using the predictions to determine the safe period of storage. The predicted and experimental in-pack partial pressures of O2 and CO2 were in fair agreement with each other. In the OPP film packages, the O2 and CO2 levels stabilized around 6.87 and 12.93 kPa, respectively. Whereas, O2 levels decreased drastically in LDPE and PP film packages. A combination of predicted in-pack environment in all the film packages, storage time and whiteness of mushroom led to the conclusion that mushrooms can be stored safely for 32, 44 and 108 h in the gaseous environment available in the LDPE, PP and OPP film packages, respectively. PRACTICAL APPLICATIONS The empirical approach followed in this study through assimilation of various transient state in-pack variables with a single qualitative attribute of mushroom can serve as a measure of assessment of the mushroom's safe storage period under modified atmosphere packaging. Further, the mathematical approach suggested in this study can also serve as a benchmark for its application to other fruits and vegetables, taking into consideration their respective limiting qualitative characteristics. Thus, the results detailed in the study can be easily applied for their direct practical application during storage as well as for further academic exercises.

Modelling Moisture Uptake by Binary Mixtures of Products Packaged in Polymeric Films

In this paper a mathematical model for prediction of moisture gain over storage time for binary mixtures of moisture sensitive products was developed, which considered both the moisture transfer through the polymeric film to the headspace and from the headspace to the product. Moisture content within the product was assumed to be uniform for a given time and to relate to the headspace humidity by the GAB sorption isotherm. The transient period of these experiments was used to estimate the mass transfer coefficients. The model was validated by monitoring the moisture take up by breakfast cereal and chocolate powder mixture in different materials, oriented polypropylene (OPP) and low density polythelene (LDPE), during storage at 25°C and 75% relative humidity (RH). The model showed that for mixes some bias was clear, particularly for the cereal, probably owing to interactions between the products. If the resistance of the product to moisture uptake were not taken into consideration, the model would over-predict the experimental results by up to 20%.

A Mathematical Model to Predict Moisture Uptake of Dry Products Packaged Individually in Flexible Films

This work present a model for prediction of moisture gain over storage time for individually packaged, which considered both the moisture transfer through the polymeric film to the headspace and from the headspace to the product. The transport of moisture between the headspace and each product was assumed to be controlled by external resistance. No interaction between the packaged components was considered. Moisture content within the product was assumed to be uniform for a given time and to relate to the headspace humidity by the GAB sorption isotherm. The isotherm parameters were determined by equilibrating samples at different relative humidity. The transient period of these experiments was used to estimate the mass transfer coefficients. The model was validated by monitoring the moisture take up by breakfast cereal and chocolate powder packed individually in different materials, oriented polypropylene (OPP) and low density polythelene (LDPE), during storage at 25°C and 75% RH (relative humidity). The model provided very good fits for the products packaged individually (with r2 above 0.99).