纳米纤维素涂层软包装材料的制备及其隔氧性能评价

Preparation of cellulose nanocrystals coated soft packaging material and evaluation of its oxygen barrier performance

为了将纳米纤维素优良的阻隔性能在食品包装材料上进行应用研究,该试验通过将纳米纤维素(cellulose nanocrystals,CNs)涂层在4种软包装基材上进行涂覆并对其性能进行评价。研究结果表明,纳米纤维素均匀的涂覆在4种基材表面,且与原始基材相比,带涂层材料表面的摩擦系数显著降低,隔氧能力得到了显著的提升,但是CNs涂覆方式并未能很好的改善复合膜的光学性能。试验结果表明带CNs涂层的取向聚酰胺薄膜(oriented polyamide,OPA)制得的复合膜隔氧效果最好,其隔氧系数为0.003 cm3·μm/(m2·24h·k Pa),相比于聚对苯二甲酸乙二醇酯薄膜(poly ethylene terephthalate),PET),赛璐玢薄膜(cellophane,CELL),定向聚丙烯薄膜(oriented polypropylene,OPP)3种基材,其隔氧系数显著降低。应用隔氧系数最高的取向聚酰胺薄膜(oriented polyamide,OPA)制作的隔氧膜对鲜切苹果进行包装保鲜,在温度为3~5℃条件下贮藏4 d,与对照组相比,以OPA为基底的隔氧复合膜在第4 d时的亮度值提高了11.7%,且其营养成分指标可滴定酸、维生素C含量和可溶性固形物含量分别提高了1.05倍、42.6%和36.2%。本研究制得的复合膜隔氧性能优异,可以较为显著的增强原始基材的隔氧效果进而延长了对氧气较为敏感食品的货架期。

In this paper,the preparation process of nanofibers with oxygen barrier materials was studied and the oxygen barrier effect of cellulose nanocrystals(CNs)coatings on 4 kinds of flexible packaging substrate was compared.The preparation process was as follows:First,the nanocellulose crystal with 1%content was prepared by the method of acid hydrolysis,and then a suitable amount of nanoscale crystal was dissolved in the distilled water by ultrasonic dissolution.When it became clear and transparent,the nanoscale coating solution with a concentration of 8%was obtained.The corresponding composite film was prepared by placing 4 kinds of substrate on a coating machine and the coating liquid was uniformly applied to the surface of the substrate at a coating speed of 2.5 mm/s.The obtained composite film was observed under an atomic force microscope.The results showed that the nanocellulose was evenly coated on 4 kinds of substrate to form a dense composite membrane structure.Moreover,the surface roughness of coated materials was significantly reduced,making it difficult for microorganisms to pollute the membrane.Based on the evaluation of the basic properties of the composite film,it was found that the coefficient of friction on the surface of the coated material was significantly lower than that of the original substrate except the oriented polypropylene(OPP)film,making the resulting composite membrane easier to mass-produce on high-speed packaging machines.The CNs coating method did not improve the optical properties of the composite film very well,and its optical performance was not significantly different from that of the original substrate.Evaluation of the oxygen barrier performance of the composite membrane revealed that CNs coating greatly increased the oxygen barrier properties of the substrate.The oxygen barrier performance of the original basement membrane was greatly improved by the composite film coated with CNs.The oxygen transmission of all composite films decreased by more than 98%,except the composite film made by OPP substrate.The application of the composite membrane on fresh-cut apples showed that the 4 kinds of oxygen-insulating composite membranes could effectively prevent the infiltration of oxygen,which effectively inhibited the decrease of the color of fresh-cut apple slices and the loss of its nutrients.The experimental results also showed that the oxygen isolation effect of oriented polyamide(OPA)film coated with CNs was the best,and the oxygen isolation coefficient was 0.003 cm3·μm/(m2·d·kPa).Compared to PET(polybutylene terephthalate),CELL(celluloid)and OPP film,the oxygen coefficient of OPA film was increased significantly,respectively.The fresh-cut apple was stored for 4 d under the temperature of 3-5℃.On the 4th day,compared with the control group,the luminance value of the OPA based oxygen insulating composite membrane was increased by 11.7%,and the contents of titratable acid,vitamin C and soluble solids increased by 105%,42.6%and 36.2%respectively.This study provides a completely new process for the preparation of oxygen barrier membranes and a new method for preventing browning and preservation of fresh-cut apples.