Impact-modified and unmodified L-polylactide and L-polylactide-polycaprolactone co-polymer films were evaluated for their suitability as materials for cheese packaging. The polymers were in some cases compounded with nanoclays as a possible route to enhanced barrier properties and/or with cyclodextrin complexes designed to provide slow release of encapsulated antimicrobials for control of mould growth on packaged cheeses. The materials demonstrated complete biodegradation under controlled composting conditions and the extruded films had acceptable transparency. Moisture uptake by films and a decrease in polymer molecular weight with time of exposure to high humidity were identified as areas of concern, although the polymer stability experiments were undertaken at 25°C and stability at normal cheese storage temperatures (~4°C) is expected to be better. Nanoclay addition enhanced the thermal stability of the polymer but reduction of oxygen and water vapour permeability to target levels through incorporation of 5% w/w nanoclay was not achieved, possibly in part due to inadequate dispersion of the nanoclays in the chosen polymer matrices. On the positive side, a novel impact-modified polylactide was developed that overcame problems with brittleness in unmodified L-polylactide and L-polylactide-polycaprolactone copolymer films, and tests indicated that a cyclodextrin-encapsulated antimicrobial (allyl isothiocyanate) incorporated in L-polylactide-polycaprolactone co-polymer films would be effective in controlling fungi on packaged cheeses. Migration of substances from the L-polylactide or L-polylactide-polycaprolactone films into cheese is not expected to be a problem.

ENS ENS ENS R R R R RISBO ISBO ISBO ISBO ISBO ABSTRA ABSTRA ABSTRA ABSTRA ABSTRACT CT CT CT CT: : : : : The effect of moistur The effect of moistur The effect of moistur The effect of moisturThe effect of moisture sorption on stability of poly(lactic acid) (PL e sorption on stability of poly(lactic acid) (PL e sorption on stability of poly(lactic acid) (PL e sorption on stability of poly(lactic acid) (PL e sorption on stability of poly(lactic acid) (PLA) films at food-packaging condi-A) films at food-packaging condi-A) films at food-packaging condi-A) films at food-packaging condi-A) films at food-packaging conditions, obtained by different humidities (11% to 98% RH) and temperatures (5 °C and 25 °C), was investigated by tions, obtained by different humidities (11% to 98% RH) and temperatures (5 °C and 25 °C), was investigated by tions, obtained by different humidities (11% to 98% RH) and temperatures (5 °C and 25 °C), was investigated by tions, obtained by different humidities (11% to 98% RH) and temperatures (5 °C and 25 °C), was investigated by tions, obtained by different humidities (11% to 98% RH) and temperatures (5 °C and 25 °C), was investigated by decrease in number average molecular weight ( decrease in number average molecular weight ( decrease in number average molecular weight ( decrease in number average molecular weight ( decrease in number average molecular weight (M M M M M n n n n n ) and loss of tensile strength. Hydrolysis of the PLA ester linkages ) and loss of tensile strength. Hydrolysis of the PLA ester linkages ) and loss of tensile strength. Hydrolysis of the PLA ester linkages ) and loss of tensile strength. Hydrolysis of the PLA ester linkages ) and loss of tensile strength. Hydrolysis of the PLA ester linkages resulted in a 75% decrease over 130 d at 25 °C and 98% RH. At cooling conditions the decrease amounted to 35%. resulted in a 75% decrease over 130 d at 25 °C and 98% RH. At cooling conditions the decrease amounted to 35%. resulted in a 75% decrease over 130 d at 25 °C and 98% RH. At cooling conditions the decrease amounted to 35%. resulted in a 75% decrease over 130 d at 25 °C and 98% RH. At cooling conditions the decrease amounted to 35%. resulted in a 75% decrease over 130 d at 25 °C and 98% RH. At cooling conditions the decrease amounted to 35%. An equilibrium moisture sorption isotherm could not be determined as the irreversible hydrolysis of PLA induced An equilibrium moisture sorption isotherm could not be determined as the irreversible hydrolysis of PLA induced An equilibrium moisture sorption isotherm could not be determined as the irreversible hydrolysis of PLA induced An equilibrium moisture sorption isotherm could not be determined as the irreversible hydrolysis of PLA induced An equilibrium moisture sorption isotherm could not be determined as the irreversible hydrolysis of PLA induced an ongoing moisture uptake. The rate increased when the humidity and temperature increased from 5 °C to 25 °C. an ongoing moisture uptake. The rate increased when the humidity and temp...

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Light-induced oxidation of semihard cheese has been evaluated by fluorescence spectroscopy. The cheese was packaged in two packaging materials and exposed to different storage conditions, which included light/dark storage, oxygen availability, and storage time (0, 4, 7, 14, 21, 42, 70, or 84 days). Fluorescence excitation-emission matrices (EEM) were analyzed by PARAFAC, which gave an estimation of the pure excitation and emission spectra of the fluorophores and the concentrations of these. This analysis showed the presence of components such as tryptophan, tyrosine, vitamin A, fluorescent oxidation products, and riboflavin. Effects of packaging material, light or dark storage, and storage time were seen. However, there was no effect of the oxygen availability on the fluorescence measurements. The score values obtained by the PARAFAC models and chemical and physical measurements were analyzed together by principal component analysis (PCA). The loadings showed a separation of the variables into three groups; the first group was related to oxidation, the second group was related to the degradation of both riboflavin and vitamin A, and the third group was linked to the protein structure.

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