Preparation Of Arabic Gum Composite Coolant And Its Application In The Preservation Of Blueberry

With the development of science and technology,people are increasingly demanding for fresh and high-quality fruit and vegetable.It is a great challenge for us to ensure the quality of fruit and vegetable during the transportation and storage based on cold-chain logistics technology.China is not only a country with a huge production of fruit and vegetable,but also a country with huge circulation loss.The main reason for this situation is the incapability of the cold-chain logistics,which leads to the high temperature in the environment and a short preservation period.It is necessary to develop a phase-change material with great performance,which will ensure that fruits and vegetables are maintained in a certain low temperature environment,reduce their intensity of respiration,and reduce the loss in the transportation.Therefore,this study used natural edible colloids as a thickener to develop a compound phase-change material with good thermal performance without pollution,and used blueberries as the experimental object to verify the application value of this phase-changed material.The main results are as follows:(1)The gel and freeze-thaw conditions of 13 kinds of natural edible colloids were investigated.It was found that the arabic gum had good cooling rate and cold preservation effect,and no phase separation.Then,the effects of the concentrations of sodium chloride and glycerol and the kinds of nano-particles on the phase transition temperature and latent heat of liquid coolant were studied by single factor experiment.The results showed that with the increase of the concentration of Na Cl and glycerol,the phase transition temperature gradually decreased,while the latent heat of phase transition gradually increased,and the effect of silicon dioxide on the latent heat of phase transition was smaller and the cost was lower.Based on the above conclusions,the main formulation of the coolant is as follows: 2% sodium chloride,0.01% nano silicon dioxide,0.5% glycerol and water.Under this condition,the phase transition temperature of the coolant is-5.37℃,and the latent heat of phase transformation was 326.8 J/g.(2)The addition amount of gum arabic in the compound coolant was investigated.It was found that the phase transition temperature showed a trend of increased first and then decreased under the concentrations of 0%,0.3%,0.6%,0.9% and 1.5%.However,the latent heat decreased first and then increased,and the holding time and the supercooling degree decreased gradually.Considered the optimum dosage of gum Arabic was 1.5%,the phase change temperature and latent heat of the composite coolant were-4.73℃ and 321.97 J/g,respectively.The supercooling degree was only 0.067 and the cold preservation time was longer,and the performance was more stable.In order to study the effect of gum arabic on the coolant,the ice-crystal states of 0% and 1.5% gum arabic were observed by fluorescence inversion microscope,it was found that the aggregation of ice-crystals in 1.5% Arabic gum and nucleation was obvious.The results showed that the arabic gum coolant had lower phase transition temperature and supercooling degree,and could maintain lower temperature of storage environment and meet the requirement of fruit and vegetable transportation.(3)The effect of arabia gum composite coolant on blueberry was studied by comparing with the control group without coolant and the treatment group with water and commercial coolant.The results showed that the arabic gum coolant could maintain the low temperature environment in the box for a long time and keep the low temperature below 12℃ for 24 hours compared with other treatment groups.Moreover,the arabic gum coolant inhibited the activities of PPO,POD and PG,and maintained the scavenging rates of DPPH and ABTS and high antioxidant activity,and promoted the accumulation of total phenol and anthocyanin,thus ensured better hardness,color and soluble solid content with better sensory quality.