| Starch has good film-forming properties,and the prepared film is non-toxic,odorless,and has high transparency.However,it has problems such as strong hydrophilicity and poor mechanical properties.Agar is a natural polysaccharide obtained from seaweed,which has advantages such as renewability,biodegradability,and good gelling properties.Mixing starch and agar to prepare a composite film can effectively improve the mechanical and waterproof properties of pure starch film.Anthocyanins are p H sensitive and can be added to starch/agar composite membranes to monitor the freshness of food.However,the poor stability of anthocyanins limits their application.This article uses hydroxypropyl cross-linked starch and agar as film-forming materials to prepare p H responsive starch/agar anthocyanin composite membranes by adding five different sources and different contents of anthocyanins.The structural and physicochemical characteristics of the membranes were studied,and anthocyanins were further embedded to prepare nanocomposites.anthocyanins were added to the starch/agar membrane to improve the stability of anthocyanins,and applied to monitoring the freshness of milk,pork,and fresh shrimp.The main research findings are as follows:（1）The addition of different anthocyanins has a significant impact on the performance of starch/agar membranes.The addition of anthocyanins improved the opacity and water vapor barrier of starch/agar membranes,and reduced the water content of the membranes.The starch/agar anthocyanin film is sensitive to p H and volatile ammonia response,and the color intensity is proportional to the amount of anthocyanin added.The starch/agar-L.ruthenicum anthocyanins film（SA-LRA）has the highest sensitivity and best color rendering.The membrane with a 4%addition of anthocyanins exhibits the best performance.（2）Different plant sources of anthocyanins have a significant impact on the structure and application performance of starch/agar membranes.Scanning electron microscopy showed good compatibility between anthocyanins from purple potatoes（PSA）and black rice（BRA）and the substrate,without phase separation.Fourier transform infrared spectroscopy confirmed the existence of intermolecular forces between anthocyanins and the film-forming matrix.The X-ray diffraction pattern shows that the addition of anthocyanins has little effect on the crystallinity of starch/agar membranes.The antioxidant test showed that the starch/agar anthocyanin membrane had the ability to scavenge DPPH radicals,while the SA-LRA membrane had the highest antioxidant activity（86.27%）.In the color stability test,starch/agar purple potato anthocyanin film（SA-PSA）and starch/agar black currant anthocyanin film（SA-BCA）showed better stability.Different sources of anthocyanin films have shown color changes in monitoring the freshness of milk and pork,which can be used to indicate the freshness of milk and pork.Among them,SA-LRA film has the best color rendering effect.（3）Anthocyanins-loaded nanocomplexes have a significant impact on the performance of starch/agar membranes.The average particle size of the anthocyanins-loaded nanocomplexes is 355.97 nm,the zeta potential is+5.17 m V,the polydispersity index is 0.32,and the embedding rate is 44.9%.Compared to the non embedded starch/agar-L.ruthenicum anthocyanins film,the nanocomposite film has higher tensile strength（6.75 MPa）and Young’s modulus（205.05 MPa）,as well as the lowest water vapor permeability coefficient(1.45×10-10 g m-1s-1 Pa-1)and good color stability.Both membranes can effectively indicate shrimp spoilage,but anthocyanins-loaded nanocomplexes membranes have better stability and are more suitable for practical applications. |
PDF Full Text Request