Characteristics And Application In Brewing Of Okra

Okra is a kind of vegetables with the properties of intensive growing period and short shelf life.Therefore,it is essential to study proper harvest stages and drying methods for okra effective utilization.Okra polysaccharides had the high viscosity.Putting okra into cloudy beer brewing process could improve the nutrition contents,give cloudy beer new flavour,rise the viscosity and turbidity of cloudy beer,improve yeast suspending power in cloudy beer and rich the types of beer.The main conclusions were listed as following:(1)Effect of harvest stages on nutrition and volatiles in okra fruitsThe okra named 'lujian' as material,the results indicated that growth rate of okra fruit was higher but dry matter content was lower after flowering 7 d?9 d.However,the insoluble dietary fiber content increased,while soluble dietary fiber content decreased rapidly after flowering 11d.Along with the delay of harvest stages,the contents of protein,amino acid,total sugar,soluble sugar and ash decreased,whereas the total phenol,flavones were higher by 14.10%and 5.16%respectively after flowering 11d than 7 d.Although pectin relative content at 11 d decreased about 12.08%comparing with 7 d;fresh fruit weight increased nearly twice and made total pectin increasing.The major volatiles of different harvest stages included dimethyl sulfide,2-methyl furan,3-methyl butanal,2-ethyl-5-methyl tetrahydrofuran,2H-pyran-2-methanol,tetrahydro-,1-hexanol,2-nonenal(E),tetradecanal.The relative contents of dimethyl sulfide,2-methyl furan,1-hexanol,tetradecanal decreased with the increase of flowering days.3-methyl butanal,2H-pyran-2-methanol,tetrahydro-,2-nonenal(E)showed opposite trend.The fruit volatiles of different harvest stages were basically same but the relative contents had significant differences.In conclusion,fresh okra was appropriate to pick after flowering 7 d?9 d,and intensive processing with functional components after flowering 11d.(2)Effects of drying methods on nutrition and antioxidant capacities in okra fruitsFresh okra fruits as the test material,were dehydrated by hot-air drying(HD),freeze drying(FD),microwave drying(MD)and natural drying(ND),respectively.As the result stated,the total dietary fiber,sugar,total nitrogen and ash contents of okra fruits were not affected by these drying methods.Among four drying methods,the FD sample has the highest soluble dietary fiber(14.21%),pectin(7.38%),flavonoid(1.72%),and Vc(322.7 mg/kg)content that had no significant difference with fresh okra fruits(p>0.05).The total phenol content of okra fruits decreased after post-drying.The total reducing capacity of okra fruits dehydrated by ND was the lowest(0.767 mmol/L),but the total reducing capacity of okra fruits dehydrated by other drying methods were same as fresh okra(0.856 mmol/L)that had no significant difference.For the scavenging capacities against DPPH and · OH,FD sample and fresh fruits were better than the other frying methods.However,the scavenging capacity against O2-· of fresh okra was significantly higher than any other drying method.Consequently,freeze drying method,which could retain the nutrition and antioxidant capacity of fresh okra,should be the primary processing method to make ready-to-eat okra food.When it comes to natural drying method,due to the benefits of naturally dried okra fruit such as low cost,large processing load,and high pectin content,it could be applied for food intensive processing required for dehydration of okra.(3)Separation,purification and physicochemical property analysis of okra water-soluble polysaccharidesThere was a significant difference between crude polysaccharide and refined polysaccharide.The optimum adding amount and hydrolysis time of amylase(4000 U/g)and protease(16 U/g)for polysaccharide purification were 50 ?L 10 min and 100 ?L 2 h.The galacturonic acid,nitrogen,ash and xylan contents of crude polysaccharide were 48.62%,1.37%,10.81%,2.69%,respectively.Molecular weight was 1.319×103 kDa and intrinsic viscosity was 294.69 mL/g.The galacturonic acid,nitrogen,ash and xylan contents of refined polysaccharide were 62.47%,0.49%,5.750%,1.12%,respectively.Molecular weight was 2.050×103 kDa and intrinsic viscosity was 332.15 mL/g.Comparing with crude polysaccharide,the galacturonic acid content of refined polysaccharide increased by 28.49%,ash and xylan decreased 46.81%and 55.02%,nitrogen decreased 64.23%.Calcium ion content,the highest in refined polysaccharide,was 0.164%.Sodion and potassium ion were the second and third,0.146%and 0.064%,respectively.The total hydrolyzed monosaccharide of crude and refined polysaccharides were 16.73%and 13.47%.The refined polysaccharide did not contain mannose and glucose.The group distributions of both polysaccharides were similar.Their peak temperatures of differential scanning calorimetry were 127.8 ? and 116.2 ? with well thermal stability.The exothermic peak of refined polysaccharide was more intensive.As for rheology,both polysaccharides were pseudo-plastic fluid exhibited shear thinning behavior.The refined polysaccharide at levels from 1%to 4%that exhibited a linear positive correlation with the zero shear viscosity in logarithm.For oscillatory measurements,the 4%refined polysaccharide showed an elastic behavior(G'>G")over a wide range of frequencies(1 rad/s?10 rad/s),at a stress of 6 Pa,while the concentration below 2%showed predominantly viscous responses(G'<G")over the same frequency range.(4)Preparation of Okra beerOkra were added to wort to brew okra beer,determined the dried okra optimum adding proportion was 0.1%?0.5%.The chromaticity,turbidity and viscosity increased 4.05%?34.46%,20%?60%,and 7.14%?28.57%comparing with control beer.The alcohol of control beer was higher than okra beer,while the acid was lower than the latter.The colour of okra beer was golden yellow and the foam was rich,white and smooth with typical malty and okra aroma.The fragrance was pure and coordinates.Okra tasted outstanding and residual clean.