Effect Of Saccharides And Alcohols With Different Chemical Structures And Molecular Weight On Performances Of Starch Based Films

Food packaging research is currently focusing on manufacturing starch-based packaging materials with high levels of safety and performance.Several countries have passed regulations putting restrictions on the application of disposable plastics.Starch is gaining attention in developing a good food packaging film that would be renewable,biodegradable,and environment friendly.The starch-based biodegradable packaging film can be used as a barrier to control water evaporation,oxygen entry,fat oxidation,and the loss of volatile substances to save the quality of processed food products and increase their shelf-life.Furthermore,starch film can be used to develop edible packaging since starch is the most popular food ingredient.The food industries have widely accepted edible starch films as a new packaging material for food safety and nutritional enhancement.Because of their global presence,processability,and cost-effectiveness,edible films made of starch have gained popularity in the packaging industry.Various processing technologies like film casting,injection moulding,and blow moulding have been developed for starch-based materials.However,a well-recognized weakness of starch film is its brittleness,especially under dry conditions.Meanwhile,the hydrophilic nature of starch prevents its function as a matrix for developing starch-based materials.Due to its hydrophilic behaviour and high-water absorption ability,a film’s mechanical and thermal properties,particularly tensile strength and brittleness,deteriorate upon dehydration.So,to overcome these problems,we have explored the development of starch film,particularly the influence of various saccharides and alcohols with different molecular weights and structures as a plasticizer on starch film’s mechanical and structural performances.Furthermore,the starch matrix was plasticized using other substances having hydroxyl groups with distinct molecular weights and chemical structures to avoid these constraints.In addition,various saccharides and alcohols with differing molecular weights and chemical structures were used to enhance starch-based films’ thermomechanical and physiochemical characteristics.We applied saccharides with different structures and molecular weights in the first study.We evaluated them as a plasticizer for starch-based materials,in which the saccharides from monosaccharides,such as glucose,mannose,fructose,xylose,and disaccharides,including sucrose and maltose,to dextrin with different molecular weights,were used.As expected,starch and these saccharides are compactable and miscible since they have similar chemical components.These saccharides must work with water or polyols to function as co-plasticizers since they are all in solid-state under dry conditions.Many monosaccharides or disaccharides with ring structures can stably stay in the starch matrix without significantly affecting the polymer chains’ microstructures.However,the monosaccharides with linear forms,such as fructose and xylose,showed much more efficiency in destroying the ordered structures and enhancing the movement of polymer chains,resulting in higher plasticization efficiency.All these saccharides can generally increase the stability of moisture contained in the starches because of the strong bonding by hydroxyl groups.Thermal properties of the starch-based films were investigated by differential scanning calorimetry,thermal-gravimetric analysis,and dynamic mechanical analysis,and morphologies and microstructures were studied by scanning electron microscopy and X-ray diffraction.These saccharides did not affect the gelatinization temperature of the starch.Tg and starch crystallinity were decreased with added saccharides,indicating that the rigid crystalline range in starch was destroyed.This research increased the knowledge of the plasticizing mechanism and can be used for developing various starch-based products,including food and packaging.In the second study,we investigated the effectiveness of various alcohols as plasticizers for starch-based materials.Specifically,the impact of molecular structures,such as the number of hydroxyl groups,molecular weights,and chemical structures of these compounds,on the performance of starch-based films has been studied.Several alcohols were used,including mono-alcohols(propanol,butanol,pentanol,and hexanol),di-alcohols(ethylene glycol,propanediol,butanediol,and pentanediol),and polyols(glycerol,erythritol,xylitol,sorbitol).Tensile testing and DSC,TGA,DMA,XRD,and SEM characterization of the starch film were used to assess plasticizing effectiveness.Alcohols with low-OH groups,such as mono-alcohols,are not retained in the starch matrix because their compatibility with starch is low.A long alkyl chain in the alcohol reduces compatibility with the starch matrix even more.This type of material had low or no plasticizer efficiency.Di-alcohols are more compatible with starch,especially those with short alkyl chains like ethylene glycol.Polyols with many-OH groups are more compatible with starch.The effectiveness of these alcohols as starch plasticizers is proportional to the number of-OH groups present.All alcohols,whether liquid or solid,must facilitate water’s action.Water acts as a gelatinizing agent and a plasticizer,so the compatibility and stability of these alcohols not only with/in starch but also with/in water is critical.We found that lower glucose and mannose concentrations did not impact mechanical properties.As the concentration of glucose or mannose increased,the modulus and strength of substances with a low molecular weight decreased.These saccharides with a lower molecular weight decreased the tensile strength(elongation)and starch plasticizing performance.As elongation increased,fructose and xylose increased the toughness of the starch film.The sugars fructose and xylose promoted elongation.The presence of fructose and xylose reduced modulus and tensile strength.Sucrose and maltose did not affect starch plasticity.These polysaccharides with low molecular weight decreased modulus and tensile strength with no significant elongation.The increase in elongation and modulus provided strong evidence of adhesion between the saccharides,alcohols,and starch matrix.Saccharides did not affect the gelatinization of starch.The hydroxyl groups of saccharides predominantly faced hydroxyl groups in the starch matrix,decreasing the water contact angle(CA).However,linear fructose and xylose slightly increased CA,indicating that they increased the hydrophobicity of the starch film.Adding dextrin showed minimal mechanical properties;modulus and tensile strength decreased significantly,and dextrins of different molecular weights all decreased the elongation of starch film.Further,more hydroxyl groups and shorter alkyl chains are anticipated to improve starch compatibility.The contact angles with water decreased after adding these alcohols,particularly polyols containing more hydroxyl groups,indicating that the hydrophilic properties of the starch film increased.The plasticization of saccharides and alcohol films resulted in an increase in elongation and a decrease in tensile strength and modulus.All materials used in this study are edible,so all developed films plasticized with various saccharides and alcohols can be used as edible and biodegradable packaging.