Effects Of Different Drying Methods On Edible Quality And Application Characteristics In Bread Of Hawthorn Powder

Hawthorn（Crataegus pinnatifida Bunge）is a fruit with the same origin of medicine and food.It contains a lot of pectin,flavonoids,vitamins and other nutrients.It has high nutritional value and health care function.This paper aims to study the drying characteristics of hawthorn and the edible quality and application characteristics of hawthorn powder prepared after drying.The main results are as follows:1.The effects of different drying methods on the drying characteristics of hawthorn and the structure and properties of pectin,an important functional component of hawthorn,were compared and analyzed.The results show that freeze drying rate is the slowest and accelerate with the increase of hot air temperature and microwave power.Freeze drying and convection drying belong to deceleration drying.Microwave drying belongs to deceleration drying in the early and late stage,and constant speed drying in the middle stage.The three common models can represent the changes of moisture during freeze drying,convection and microwave drying.Newton,Henderson and Pabis and Parabolic models fit the moisture curves of freeze drying,convection and microwave drying better respectively.The physicochemical properties,rheological properties,gel properties and emulsifying properties of pectin treated by different drying methods are different.All pectin galacturonic acid（Gal A）contents are more than 65%,The degree of esterification is more than 50%,which belongs to high methoxy pectin.Fourier transform infrared spectroscopy（FT-IR）shows that the pectin obtained by different drying methods have pectin characteristic functional groups,indicating that the pectin structure had not changed.The main chain length,side chain branching degree,molecular weight and particle size decrease gradually with the increase of convection temperature and microwave power.The apparent viscosity decreases with the increase of shear rate,convection temperature and microwave power.Both have good gel and emulsifying properties.2.The effects of different drying and grinding methods on the edible quality of hawthorn powder were analyzed.The results shows that under the same grinding conditions,the D₅₀ and volume average diameter of hawthorn powder obtained by freeze drying are lower than those obtained by other drying treatments,and the specific surface area,cell fragmentation rate,water holding capacity,oil holding capacity,water solubility index,flavonoids and polyphenols content are higher than those obtained by other drying treatments.With the increase of convection temperature and microwave power,it gradually increased.It shows that it has better hydration,processing properties and biological activity.Under the same drying conditions,the D₅₀ and volume average diameter of hawthorn powder obtained by ball milling are lower than those obtained by high-speed shear,and the specific surface area,cell fragmentation rate,water holding capacity,oil holding capacity,water solubility index,flavonoids and polyphenols are higher than those obtained by high-speed shear.It shows that it has better edible quality.3.The effect of hawthorn powder on bread properties was analyzed.The results show that hawthorn powder had no significant effect on bread texture and sensory properties.The digestibility of starch,the content of rapidly digestible starch（RDS）,slowly digestible starch（SDS）and the estimated glycemic index（EGI）in bread decreased,while the content of resistant starch（RS）increase.It can effectively inhibit the digestion rate of starch in bread and enhance the nutritional characteristics of bread.