Preparation Of Nano Preservative Film And Its Preservation Research On Golden Needle Mushrooms (Flammulina Velutipes)

With polyethylene (PE) as the main material, add four nanometer active particles (nano-Ag, nano-TiO2,nano-SiO2, nano-attapulgite) and anti-fog masterbatch, prepare a new polyethylene (PE) nano preservative film and research its preservation effect on Flammulina velutipes, at the same time, packaging some Flammulina velutipes with the normal preservative film and no packaging as control. Measure the Flammulina velutipes’ organoleptic indicator (weight-loss rate and browning degree (BD))、nutritional index (soluble protein、soluble solids and VC)、physiological index (respiratory intensity, malondialdehyde (MDA)、membrane permeability and antioxidant enzymes activity, et al.) in the storage period. The main research results were as follows:1. A mixture of 15 wt.% of nano-powders (30 wt.% of nano-Ag,35 wt.% of nano-TiO2, 25 wt.% of nano-attapulgite and 10 wt.% of nano-SiO2),46 wt.% of LDPE,22% wt.% of LLDPE,10 wt.% of dispersing agent,5 wt.% of lubricant and 2 wt.% of cross-link reagent immingled for 0.5 hour was fed into a co-rotating twin screw extruder and cut into masterbatch nano-granules. Then immingle 7.5 wt.% of the prepared nano masterbatch,8 wt.% of anti-fog masterbatch and 84.5 wt.% of LLDPE, and cast into a film of 18μm thickness via a double-layer co-extrusion casting machine.2.The morphological characterization, tensile strength, nominal strain fracture, angle tear strength, light transmission, oxygen permeability, water vapor permeability, penetration rate of carbon dioxide, anti-fog effect of nano preservative film were conducted. The results indicated that nano-particles were evenly distributed in the nano preservative film, tensile strength and some other physical indexes, oxygen permeability and penetration rate of carbon dioxide compared to normal film had improved, which contribute to maintain a suitable air environment, water vapor permeability drop, which can reduce water evaporation, anti-fog properties was enhanced, all of these were helpful for the fresh-keeping of edible mushroom. Secondly, the hygienic property of nano preservative film is conformity to the GB 9687-1988《Hygienic standard for polyethylene products used as food containers》.Thirdly, according to GB 9685-2008《Hygienic standards for uses of additives in food containers and packaging materials》,the nano-particles (Ag、TiO2、SiO2 and attapulgite) were allowed to be added into the preservative film in a right amount.3.By taking Flammulina velutipes which people like to eat in daily life, but tend to browning、opening the cap、elongating the handle、spoiling in the storage period as the research object, study the fresh-keeping mechanism of nano preservative film for it. Flammulina velutipes (250g per case) during the 15d storage at 4℃, nano preservative film slowed down the phenomenon that opening the cap、browning、water loss,et al.The results indicated that the weight-loss and browning degree (BD) lower than normal film by 17.35% and 7.46%, soluble protein、soluble solids and VC content maintained 3.28mg·g-1、6.1% and 8.03μg·mg-1 prot, which were significant more than normal film which just maintained 2.46 mg·g-1、5.03% and 7.67μg·mg-1 prot.Activities of SOD, POD and CAT were improved by 44.27%、57.02% and 8.47% respectively, respiratory intensity、superoxide anion free radical、H2O2、MDA and membrane permeability were inhibited by 15.73%、20.97%、4.75%. 19.94% and 10.59% respectively, the Flammulina velutipes with no packaging had the worst quality compared to normal and nano packaging.Nano preservative film kept Flammulina velutipes antioxidant enzymes activity in a high standard, effectively swept the superoxide anion free radical and H2O2 away, slowed down the senescence of Flammulina velutipes in the post-harvest,meanwhile, reduced the loss of nutrient content,inhibited the respiratory intensity and membrane lipid peroxidation, protected the structure of cell membrane, extended Flammulina velutipes’storage period.