Study On Physicochemical Properties Of Electrolyzed Water With Negative Redox Potential And Its Effect On The Quality Of Cold-brewing Tea

As consumers attach great importance to health,drinking water requirements change from health safety to functional health.The electrolyzed water with negative oxidation-reduction potential（ORP）has certain anti lipid peroxidation ability and has good adjuvant therapeutic effect on many diseases.Compared with hot tea,cold tea has lower caffeine content,less bitter taste and better taste.However,at present,there are some problems,such as less leaching of active components in cold tea compared with hot tea,longer brewing time,limiting industrial production and so on.Electrolytic water with negative ORP value can be used as extraction solvent because of its high negative redox potential,low surface tension and strong permeability.Therefore,exploring the corresponding relationship between the negative ORP value and p H value of electrolytic water and the relationship between the negative ORP value and p H value and the antioxidant and gastric acid neutralizing ability of electrolytic water will provide guidance and new choices for consumers’health needs of drinking water,and play a positive role in developing electrolytic water and providing reference for natural antioxidants and antacids.Secondly,it is envisaged to use electrolytic water with negative ORP value as water for cold tea making,improve the dissolution rate of biochemical components of tea,and solve the problem of low dissolution rate.Due to the simple preparation,low cost and no pollution to the environment,using electrolytic water as water for cold tea making has great industrial application prospects.At the same time,it will expand the application scope of electrolytic water and provide reference for the development and function exploration of new drinks.In this paper,by adjusting the electrolysis time to produce electrolytic drinking water with different negative ORP values,green tea,black tea and black tea were selected.Firstly,the antioxidant capacity and neutralization capacity of electrolytic water with different negative ORP values were studied;Secondly,through electrolytic water-cooled tea making with different negative ORP values,the effects of electrolytic water and bottled drinking water on the quality of cold tea were compared and analyzed,and the technical feasibility of electrolytic water as cold tea processing water was analyzed and discussed,and the most suitable cold tea making and negative ORP electrolytic water were selected;Finally,compare the effects of ultrasonic assisted cold bubble and ordinary cold bubble on the quality of tea soup,select the best cold bubble method,optimize the electrolytic water-cooled tea making process,and compare it with the standard hot tea making,so as to develop a new electrolytic water-cooled tea making beverage with good sensory quality and strong antioxidant activity,and provide reference for the selection of water for cold tea processing.The main research methods and results are as follows:（1）The basic physical and chemical properties,antioxidation and the ability to alleviate gastric acid excess of electrolytic water with different negative ORP values were studied by means of p H/ORP meter,ICP-MS,ultraviolet spectrophotometer and simulated artificial stomach model.The results showed that the basic physical and chemical indexes of electrolyzed water 1 and 2 with different negative ORP values met the relevant drinking standards of domestic soda water,and the negative ORP value of electrolyzed water was significantly positively correlated with p H value（P<0.01）.The antioxidant capacity of electrolytic water was significantly higher than that of drinking water（P<0.05）,and was significantly positively correlated with negative ORP value.Electrolytic water has the ability to neutralize gastric acid,which is significantly different from drinking water（P<0.05）.The comparison shows that electrolyzed water sample 2（obtained by electrolyzing drinking water for 4 min,ORP=-372±1.00 m V）has strong antioxidant capacity,and its superoxide anion,hydroxyl radical,ABTS radical scavenging capacity and malondialdehyde（MDA）inhibition rate are（49.06±0.16）μg Vc/m L,（1.46±0.03）μg Vc/m L,（3.00±0.08）μg Vc/m L,（20.40±1.56）%,the ability to relieve gastric acid is equivalent to 0.2%Na HCO₃.（2）The quality of electrolytic water-cooled tea with different negative ORP values was studied by means of p H/ORP meter,chromatometer,ultraviolet spectrophotometer and HPLC.The results showed that the p H value of cold tea brewed with electrolytic water（hereinafter referred to as electrolytic water）with negative ORP value was weakly alkaline,and the content of total soluble solids（TDS）and extraction rate were higher than those of bottled drinking water-cooled tea.Among them,the ORP value of electrolytic water-cooled green tea is negative,the l*value is higher than that of bottled drinking water-cooled green tea,and the l*value of electrolytic water-cooled black tea and black tea is significantly lower than that of bottled drinking water-cooled green tea.The green degree（-a*）of electrolytic water-cooled green tea is higher than that of bottled water-cooled green tea,and the water sample 2 is the largest.The yellowness（b*）of electrolytic water-cooled tea making was higher than that of bottled drinking water-cooled tea making,and the water sample 2 cold brewed black tea was the largest;With different negative ORP values,the dissolution of the active components of electrolytic water-cooled green tea was higher than that of bottled water-cooled green tea,of which water sample 2 was the highest.There was no significant difference between the dissolution of the active components of electrolytic water-cooled black tea and black tea soup and bottled water-cooled green tea except for the total amount of free amino acids and caffeine;The antioxidant activity of electrolyzed water-cooled green tea soup was better than that of bottled water-cooled green tea,and water sample 2 was the highest.The antioxidant activity of black tea and black tea made by electrolytic water cooling was lower than that of bottled water cooling;The sensory scores of electrolytic water-cooled tea making soup were higher than those of bottled water-cooled tea making,and water sample 2 was the best.（3）The effects of ultrasonic assisted extraction and ordinary extraction on the quality of electrolytic water-cooled green tea were studied and compared by means of p H/ORP meter,colorimeter,ultraviolet spectrophotometer,HPLC,headspace solid-phase microextraction and gas chromatography-mass spectrometry.The results showed that the ORP value of ultrasonic assisted extraction was negative,and the extraction rate,chromaticity value,active ingredient content,antioxidant activity and sensory quality of tea soup were better than those of ordinary extraction.The optimal technology of ultrasonic assisted electrolytic water-cooling green tea brewing was determined by orthogonal optimization experiment:tea water ratio 3/160,ultrasonic brewing temperature 30℃and brewing time 25 min.Secondly,the ORP value of ultrasonic assisted electrolytic water-cooled green tea was negative,and the extraction rate was significantly higher than that of standard hot tea（P<0.05）;The contents of active components except EGC and caffeine were significantly higher than those of standard hot tea（P<0.05）;The antioxidant activity and sensory score were significantly higher than those of standard hot tea（P<0.05）;Compared with the standard hot tea soup,which has bitter aroma and contains more unpleasant fat aroma substances,electrolytic water-cooled green tea has richer aroma components,pure aroma and slightly floral aroma.