Development of permanent chemical hydrogel films based on chitosan and carboxy methyl cellulose for moisture absorbing packaging films

Food waste is one of the world's most important problems. In medium and in high income countries, the highest amount of food waste occurs at household level. Dry foods, fresh fruits and vegetables are among the most wasted food products at household level. The main aim of this study is to develop biopolymer based chemical permanent hydrogel films which can be used as a moisture absorber/regulater in food packaging systems with an ultimate goal to prolong the shelf-life of products. In the first part of the study, semi-interpenetrating polymer network (Semi-IPNs) hydrogel films based on genipin crosslinked-chitosan (Ch) and sodium carboxymethyl cellulose (CMC) were prepared by solution-casting method. Swelling degree, thermal and mechanical properties, physical and chemical interactions within network of hydrogel films were characterized and the effect of addition of genipin on biodegradability of hydrogel films in compost environment was tested. Genipin cross-linking increased the tensile modulus, strength and thermal stability of the hydrogel films although decreased the swelling degree of the hydrogel films in water and reduced the biodegradation rate. The results indicated that the developed hydrogel films have a great potential for food packaging applications. In the second part of the study, hydrogel films were applied in food packaging systems and their efficacy in prolonging the secondary shelf-life of Turkish coffee, mushroom (Agaricus bisporus) and broccoli florets (Brassica olerecea) was investigated and performance of hydrogel films on absorbing/regulating the excessive moisture inside packaging atmosphere was studied. Sensorial quality, relative humidity within packaging atmosphere were followed for Turkish coffee stored at both room and refrigerator temperature and moisture loss behavior, microbial load, color and texture of the mushrooms and broccoli florets stored at 5°C and 25°C were analyzed. The results showed that hydrogel films can be effectively used as auxiliary packaging materials for regulating inside the packaging of high moisture containing foods which can help prolonging their shelf-life upon temperature fluctuations.