| Drinks have the function of supplementing moisture and nutrition,and have excellent taste and unique flavor,which have become a part of the daily diet of modern people.The packaging industry is developing rapidly at home and abroad,and the use of aseptic packaging technology to package beverages is widely used.However,aseptic packaging devices currently on the market have problems such as high cost,cumbersome and complicated operations,and requirement of large factory floor space.It is necessary to develop a convenient,low-cost,safe and effective aseptic packaging device.In this paper,water glass and polyvinyl alcohol solution are first mixed to obtain a casting film solution,and the surface characteristics and properties of the film are evaluated and tested after inverse molding to obtain the optimal parameter film-making process and make the film;finally,water glass-polyvinyl alcohol composite ultrafiltration membrane is applied in a self-made aseptic packaging system,and suitable beverages are aseptically filtered and packaged.The aseptic packaging filtration system is tested by evaluating the integrity of the packaging device and the number of microorganisms after packaging and storage.The full study draws the following conclusions:(1)The study developed a water glass-polyvinyl alcohol composite ultrafiltration membrane formula(5 g/100 m L of polyvinyl alcohol and 5.1%water glass content)and a method for preparing the membrane(the same proportion of polyvinyl alcohol solution and water glass solution,i.e.1:1 ratio,was mixed.The mixture was magnetically stirred for 30 minutes to make a uniform reaction.After standing for 24hours and degasing,8 ml of casting film solution were taken into a 9 mm round plastic petri dish,and dried in an oven at 30?for 24 hours.A flat membrane was prepared.After the membrane was separated from the flat,it was immersed in a 2 mol/L sulfuric acid solution for 24 hours,and then washed with pure water several times,and then soaked in pure water for use.The water flux of the sulfuric acid post-treated water glass-polyvinyl alcohol composite ultrafiltration membrane was 88.08 L/(m~2·h),its egg white protein retention rate was 87.88%,its bovine serum albumin retention rate was 93.24%,and the molecular weight of retained molecules was supposed to be<65000 Da).(2)When filtering the pre-treated drinking water,beer,and cocktails through a composite ultrafiltration membrane made of 5.1%water glass-polyvinyl alcohol,the flux of drinking water was stabilized in 30 minutes,which was 81.93 L/(m~2·h);the flux of beer and cocktail reached a stable state in 60 min,which was 44.59 L/(m~2·h)and 42.92 L/(m~2·h),respectively;when the operating pressure was-0.1 MPa the best flux is 87.05 L/(m~2·h)for drinking water,47.98 L/(m~2·h)for beer,and 52.44 L/(m~2·h)for cocktails.The solids retention was evaluated when beer and cocktails were filtered through a water glass-polyvinyl alcohol composite ultrafiltration membrane.It was found that for beer and cocktails,the solids transmittance was as high as 98%or higher.This means that the loss of nutrients or other functional compounds was low.The polluted membrane after filtration of these two beverages was cleaned by immersing in a 0.1%NaClO solution for 20 minutes,which had the advantage of energy saving,high efficiency,and capacity of environmental protection.The cleaning effect was good so that the membrane beverage flux recovery rate reached up to93.64%.(3)The composite ultrafiltration membrane made of 5.1%water glass-polyvinyl alcohol was applied to self-made aseptic packaging filtration system for beverage filtration packaging.The drinking water flux through the sterile filtration packaging system was 81.36 L/(m~2·h),the beer flux was 41.51 L/(m~2·h),and the cocktail flux was 45.46 L/(m~2·h);the solids transmittance of beer and cocktails was found to be higher than 98%.This conclusion was consistent with the data obtained in Chapter 2.These results demonstrated the integrity of the membrane in the sterile filtration packaging system.The process parameters in the self-made aseptic packaging system for aseptic packaging of the beverages were determined.The best results were obtained by using the following process parameter:2 ml/min or 1 ml/min injecting speed for portable water or beer and cocktail,respectively.The flux of portable water was stabilized after filtration for 30 min while that of beer and cocktail was stabilized after filtration for 60 min.The beverages were aseptically packaged by using the self-made sterile filter packaging system.The experimental result indicated that after 28 days of storage,the total number of microbial colonies in the beverages was within the national standard.Among them,coliforms microbes,Streptococcus faecalis,Pseudomonas aeruginosa,and Clostridium perfringens in portable water were not detected,and neither E.coli nor harmful bacteria were detected in beer or cocktails.After being stored for 180 days,the microbial indicators of all beverages tested still met the national standards.The effectiveness of aseptic filtration and aseptic packaging by using the self-made aseptic filtration packaging system was proved. |
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