Study On Multistage Partial Block Freeze Concentration To Prepare High Content Apple Cider Vinegar

Freeze concentration technology is not widely used in domestic at present,relevant reports are also very scarce,and apple have fairly rich resources in our country,after fermentation of fruit vinegar products also have a broad market.It is very meaningful for apple cider vinegar which content more water to be treated by freeze concentration cryogenic treatment technology to obtain high concentration.This study did experiment many times to improve a set of partial block freezeconcentration apparatus which were researched and developed independently for 5.0% of initial concentration of apple cider vinegar by multistage freeze concentration,and to explore the best technological conditions and the entrainment effectively recycling.At the same time,the original vinegar and different vinegar samples were analyzed in the aspect of the nutrition composition and physicochemical index.Aimed to further improve the freeze concentration technology and quality of apple cider vinegar.The specific research results are as follows:1.The 50 L partial block freeze concentration equipment was improved.In the concentration material tank,there was added a adjustable speed device which composed of three pairs of impeller that can eliminate the phenomenon of concentration polarization;the central tank which were installed a series of on-line temperature recorders can record all temperature points from cold wall to the center of material liquid;it canceled the refrigerant interlining and air gap at the bottom of the tank which led to concentrate discharged difficult;the outside air layer of material tank were connected to a feed tank,after thawing phase it can be bubbled into a next batch of feed liquid that needed to be concentrated,recycling cold and cooling the batch of material liquid,reducing overall energy consumption.Finally,finished the partial block freeze-concentration apparatus.2.It explored the apple cider vinegar two levels of concentration process optimization and the concentration effect.Through contrast experiment,the two levels concentration can be more effective with high quality,low entrainment of concentrated apple cider vinegar.The primary concentration for optimum process conditions: the first phase of the refrigerant temperature is-10.0 ? kept 3.0 h,the second is-16.0 ?,and stirring speed is 900 rpm.After 21.0 h,we can get the primary concentrate 14.74 kg of 12.5%,the primary entrainment 34.47 kg of 1.9%,as well as power consumption is 72 kW·h.The secondary concentration for optimum process conditions: the first phase of the refrigerant temperature is-16.0 ? kept 4.0 h,the second is-24.0 ?,and stirring speed is 900 rpm.After 28.0h,we can get the secondary concentrate 15.11 kg of 25.0%,the secondary entrainment 32.81 kg of 6.7%,and power consumption is 135 kW·h.The best process conditions for entrainment concentration and recovery is : the first phase of the refrigerant temperature is-8.0 ? kept 3.0 h,then lower the refrigerant temperature to-14.0 ?,stirring speed is 900 rpm.After 30.0 h,we can get the recycling solution 7.51 kg of 6.9%,and the final entrainment 21.66 kg of 0.1%,and power consumption is 77kW·h.3.It systematically compared and analyzed the retention of aromatic substances of apple cider vinegar before and after concentration.There are 14 kinds of main aromatic substances in apple cider vinegar determinated by GC-MS,among them there are 6 kinds of esters,2 kinds of alcohols,2 kinds of aldehydes and 2 kinds of phenolic acids.The characteristics of the higher content composition are benzaldehyde,octanoic acid,ethyl benzene acid-2-4-butyl ester,phenylethyl alcohol,phenyl ethyl acetate,etc.Other component content is relatively less.The ultimate entrainment aromatic substances species are less and content are small which can be discarded after concentration.The total loss rate was 2.61%.The loss rates of characteristic components are between 2.36% and 12.00% about benzaldehyde,octanoic acid,4-ethylbenzoic acid,2-butyl ester,phenylethyl alcohol,and acetic acid,2-phenylethyl ester.The taste of the solution of recovery is close to the original vinegar,while the ultimate entrainment is far away.4.It systematically compared and analyzed the retention of organic acids of apple cider vinegar before and after concentration.After primary and secondary freeze concentration,apple original vinegar organic acids total loss rate is only 3.45%,malic acid,lactic acid,acetic acid and succinic acid retention rates are between 79.10 and 88.71%.The loss rate of main organic acid,acetic acid,is only 3.03%,the whole retention rate is more than 95%.After two levels of concentration of recovery,free radical clearance rate compared to the original vinegar only reduced by 7.31%.The secondary entrainment and entrainment recovery still have high concentration and organic acids content,and the antioxidant capacity is higher too.The organic acid content in ultimate entrainment is less,radical scavenging ability is weak.