The Effect of polyolphine films coated with alpha - tocopherol in preventing the oxidation of traditional butter stored in the refrigerator

Studies in recent years have led to the emergence of a new concept in the packaging industry namely “Active packaging”. Contrary to popular packaging that needs to be completely neutral and ineffective, in different kinds of active packaging, there is an interaction with food or environment, and has an active role in food materials maintenance (Brody et al, 2008). Nowadays, various kinds of polymeric materials and their different characteristics and forms has resulted in easy design and production of packaging based on special requirements of a food product (Lopez-rubio et al, 2004). Polyethylene and polypropylene along with cardboard boxes are used for packing butter (Milts, 1988). It has been proved that Alpha-Tocopherol maintains its stability in the processing conditions and low aw also maintain its stability, alpha – Tocopherol has desirable migration characteristics and excellent solubility in polyolephines. use of alpha- Tocopherol is more affordable compared to other antioxidants (Lee, 2005; Wessling et al, 1998).The aim of this study was to investigate the effect of alpha-tocopherol coating on the surface of polymer films in preventing the oxidation of lipid in butter.
: Materials
DL-alpha-tocopherol acetate, low density polyethylene film(LDPE) , biaxial oriented polypropylene film (BOPP), traditional-lactic butter with salt made from cow's milk .
Methods Preparation of films: In this stage, first alpha-tocopherol was prepared with three concentrations of %0.1, %0.15and %0.2, and %70 ethanol was used as solvent. In the next step, low density polyethylene and polypropylene films were prepared in enough dimensions and numbers, and were washed and sterilized by %70 ethanol. Then, different concentrations of alpha-tocopherol (%0.1, %0.15,%0.2) were separately covered on a sufficient number of films via spraying (under identical conditions).to complete coverage of the films surface, spraying alpha-tocopherol was performed 3 times. after drying, films were kept in dark place (Pereira et al, 2011).
Packaging and storage of butter: At this stage, butter pieces weighing 45 grams covered with LDPE and BOPP films with three different concentrations of alpha-tocopherol (%0.1,%0.15,%0.2) were packed. To prepare the control sample, butter was packed with alpha-tocopherol lacked films. The experiments of determining the amount of peroxide and acidity, and Sensory evaluation test was conducted on a sample of butter before packaging, and were repeated in tenth, twentieth ,and thirtieth days.
Determining the amount of alpha-tocopherol remained on the films : At this stage, in order to determine the amount of alpha-tocopherol remaining on the films, weight difference of films before and after spraying alpha-tocopherol, and drying them on the films was measured. The amount was calculated by mg/cm2 stated (Contini et al, 2012).
Measurement of alpha-tocopherol migration to ethanol: The total amount of alpha-tocopherol migrate from the films into the similar lipid matter(%95 ethanol)were calculated by the colorimetric method using a standard alpha-control solution and drawing the calibration curve(Corrales et al, 2009).
The Sensory evaluation test: To evaluate the sensory properties including taste, color, smell and public acceptance, five-point hedonic test was used(Tafreshi et al, 2013).
Methods and tools for data analysis: All tests were repeated three times. For data analysis, a factorial experiment in a completely randomized design was used. Alpha-tocopherol concentration, time and type of film were the main factors. Duncan multiple range test was used to assess the differences between means in the confidence level of %5.For all statistical analysis, MSTAT-C software version 14 was used.
Findings from surveying the migration process into 95% ethanol solution, indicates that alpha-tocopherol were remained on the surface of polymeric films (LDPE &BOPP) after drying, and migrated from the surface of films into ethanol %95. With the increase of time and concentration of alpha-tocopherol, migration from the surface of films into ethanol increased (p