Abstract:
Flexible packing is steadily gaining importance in the packing industry with improved barrier
properties and lower cost compared to rigid packing. The objective of this research was to
evaluate different flexible laminates for water vapour transmission rate and identify the best
suitable material for hygroscopic foods with different flexible laminates, using critical
moisture contents of foods.
Seven types of flexible materials namely LDPE, OPP/CPP, OPP/LLDPE, PET/LLDPE,
PET/MPET/LLDPE (SL), PET/ALUFOIL/LLDPE, and PET/MPET/LLDPE (SB) were used.
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Cereal (Rice flour), Condiment (Chilly powder), Beverage (Coffee powder) and
Confectionary (Biscuit) were used as hygroscopic foods.
The hygroscopic foods were packed using above flexible laminates and kept under normal
environmental conditions. Water vapour transmission rate (WVTR) of different dried foods
were measured at absorption phase and desorption phase with different laminates. Initial
moisture content (MC) of foods, total weight of packed sample and the area of water vapour
transmission was measured. .
The value of the WVTR of the flexible laminates LDPE (1.1132g/m2 /day) and PET/LLDPE
(1.2082g/m2/ day) had higher than others at absorption phase. The lowest value of WVTR was
observed in PET/ALUFOIL/LLDPE (0.004 lg/m2/ day) than other triple laminates type such
as PET/MPET/LLDPE (SB) and PET/MPET/LLDPE (SL). It could be observed that triple
laminate has lower WVTR than single films or double laminates.
Triple laminates had taken longer time period to reach critical MC of hygroscopic foods.
Single films or double laminates can be used for rice flour, chilly powder and coffee powder if
longer shelf life is not required as it is cost effective.
More suitable laminate type for packing rice flour and chHly powder were identified as any
kind of triple laminates and PET/ALUFOIL/LLDPE respectively. Coffee powder can be
packed-safely in PET/ALUFOIL/LLDPE and PET/MPET/LLDPE (SL). Single laminates and
double laminates cannot be used for biscuit which has lowest critical moisture content value.
