Effects Of Grinding On Physicochemical Properties And Some Functional Properties Of Carrot Residue

Carrot residue is a by-product of carrot production,which is rich in dietary fiber.The by-product is not used effectively,resulting in a large amount of waste of resources.In recent years,studies have shown that dietary fiber has a certain water holding capacity,expansion,cholesterol,sodium cholate,sodium nitrite and other strong adsorption;At the same time,it can be used as an emulsifier and has good stability to the emulsion,which has potential development and utilization value.In this paper,the carrot residue was used as the experimental material,and the effects of different processing time on the nutrient composition,physical and chemical properties,functional characteristics,structure and emulsification of carrot residue were compared through grinding technology.In order to provide a theoretical basis for the development and utilization of carrot residue.The main research contents and results of this paper are as follows:(1)The effects of different grinding time on the nutrient composition of carrot residue were studied.The results showed that compared with the untreated carrot residue,the protein content(5.33-5.41 g/100g),fat content(13.59-16.56 mg/g)and water content(0.26-0.31 g/100g)of the ground carrot residue had no significant differences(p>0.05),but the yield of total polyphenols(TPC)was significantly increased(p<0.05),the highest yield of TPC was obtained when the grinding time was 30 min,and the content was 3.85 mg/g.After grinding for 40 min,the yield of TPC decreased to a certain extent,and the yield of total flavonoids(TFC)also showed the same trend.Compared with the content of TFC in untreated dietary fiber(1.07mg/g),the yield of TFC reached 1.63mg/g after grinding for 30 min.Insoluble dietary fiber(IDF)decreased from 35.13 g/100g to 23.51 g/100g with the increase of milling time,while soluble dietary fiber(SDF)increased from 9.81 g/100g to 19.72 g/100g(p<0.05).(2)The effects of different grinding time on physicochemical properties of carrot residue were studied.The results showed that the water holding capacity,oil holding capacity and expansion capacity of carrot residue were significantly increased after 30 min grinding(p<0.05).Compared with untreated carrot residue,the water holding capacity,oil holding capacity and expansion capacity at 30 min were 2.1 times,2.86 times and 1.36 times of untreated carrot residue,respectively.According to the loose density and compression index,the fluidity of the samples after grinding is still poor compared with the samples without grinding.(3)The effects of different grinding time on the functional properties of carrot residue were studied.The results showed that the adsorption capacity of the five treatments was stronger than that of the five treatments at pH=2 than that at pH=7.In terms of the maximum adsorption capacity,30 min grinding had the best effect.When pH=7,the adsorption capacity of cholesterol of carrot residue increased,but when pH=2,the adsorption capacity of cholesterol of the sample became weak.The best effect was also obtained when grinding for 30 min,which was consistent with the adsorption result of sodium nitrite.After grinding,the adsorption capacity of sodium cholate was significantly enhanced(p<0.05);In addition,both milled and unmilled samples had strong free radical scavenging ability and total reducing power,which were significantly increased after milled compared with unmilled samples(p<0.05),and with the extension of grinding time,the scavenging ability of DPPH and ABTS free radicals increased first and then decreased,and the best effect was obtained after grinding for 30 min,which was consistent with the previous results of changes in yields of polyphenols and flavonoids.(4)The effects of different grinding time on the structure characterization of carrot residue were studied.The results showed that SEM analysis showed that the microstructure of the dietary fiber in the unground carrot residue was relatively smooth,while the microstructure of the fiber after grinding was honeycomb,uneven or fragmented.X-ray diffraction analysis showed that the crystal shape of dietary fiber in the ground carrot residue was still cellulose type ?,which was the coexistence of crystalline zone and non-crystalline zone.The infrared spectrum showed that the intensity of the absorption peaks of each molecular group in the ground carrot fiber increased to different degrees,which caused the change of the scattering intensity.The results of differential scanning showed that there were endothermic peaks and exothermic peaks in the dietary fiber after grinding,but the whole fiber was in exothermic state.(5)The effects of processing conditions on the stability of carrot residue emulsion were studied.The results showed that the emulsification index,stability and emulsification of carrot residue stabilized emulsion firstly increased and then decreased with the prolonging of grinding time.When the grinding time was 30 min,the emulsification and stability of the emulsion were the best.The emulsification and stability of the emulsion increased with the increase of pH value,but the overall stability was relatively stable,and the stratification was not obvious.The emulsification and stability decreased with the increase of ionic strength and the increase of temperature.