Study On The Adsorption Of Menthone By Starch With Hydrophobic Modification And Porous Treatment

Menthone is an important flavor substance and additive in products such as flavors and daily chemicals,and has certain antibacterial and antimicrobial effects.However,the high volatility,strong hydrophobicity and heat sensitivity of menthone limit its application in multiple fields.In response to the defects of menthone,encapsulation is now commonly used to expand its application and improve the application effect.The structure and properties of the carrier are important factors affecting the encapsulation effect,so it is important to find a carrier with relatively simple preparation process,mild preparation process conditions and high loading capacity.Starch has been widely used as a carrier because of its wide source,high biocompatibility and easily modified structure.In this thesis,the binding ability between starch and menthone was enhanced by hydrophobic modification of OSA and enzymatic porous treatment with corn starch as raw material.The effects of different modification sequences on the structure and adsorption properties of the carriers were investigated to clarify the relationship between the degree of hydrophobic modification of OSA and the adsorption performance of the carriers.The mechanism of adsorption and release of menthone by the carrier was elucidated.The main contents are as follows:First,OSA hydrophobically modified and then enzymatically porous treated OSA-porous starch,and porous-OSA starch with the reverse modification order were prepared.The effects of the modification order on the starch adsorption properties,particle morphology,specific surface area,crystalline structure,substitution degree and OSA groups distribution were investigated.The results showed that the presence of OSA groups inhibited the enzymatic reaction,and the hydrolysis rate of porous-OSA starch was more than twice that of OSA-porous starch at the same enzyme addition.The number of surface pores,specific surface area and relative crystallinity of OSA-porous starch are smaller than those of porous-OSA starch,which is not favorable for OSA-porous starch to adsorb hydrophobic substances.However,porous-OSA starch had better adsorption performance,with oil absorption rate up to 121.33%.It could be found by laser confocal microscopy as well as Raman spectroscopy that the signal of OSA groups inside the porous-OSA starch granules was enhanced and the granules possessed a more consistent OSA group distribution state.Secondly,porous-OSA starch with different degrees of hydrophobic modification were prepared under enzyme addition of 2.0%for 6 h.The influence of the degree of hydrophobic modification on the starch structure was investigated by using the adsorption performance as the index.With the increase of OSA addition,the hydrophobic property gradually improved,and the maximum contact angle was 80.2°.SEM images showed that the hydrophobic modification resulted in a rough surface of the starch granules and a breakage of the granules at high OSA additions.With the increase of hydrophobic modification,a trend of increasing and then decreasing specific surface area and oil adsorption of porous-OSA starch was observed.The porous-OSA starch with 9%OSA addition had the highest specific surface area of 0.845m~2/g and the best oil absorption capacity.The high addition of OSA resulted in damage to the crystalline structure of starch,a decrease in the relative crystallinity and thermal stability of porous-OSA starch.Finally,the adsorption mechanism and release characteristics of starch on menthone were investigated by examining the interaction between porous-OSA starch and menthone.The results showed that the adsorption of porous-OSA starch on menthone could obtain a maximum loading of 64.34 mg/g by adsorption at 40℃for 120 min,and the adsorption behavior was consistent with the primary adsorption rate model.The adsorption behavior of porous starch on menthone was consistent with single molecular layer adsorption(Langmuir isotherm model),and the adsorption process of porous-OSA starch was more consistent withFreundlich isotherm model due to the presence of OSA groups.The interaction between porous-OSA starch and menthone was in the form of hydrogen bonding and hydrophobic interactions,and the alteration of XRD patterns indicated the formation of a new physical phase.The stability of menthone in the porous-OSA starch-menthone complex was significantly higher than that of the other samples,and the release properties of menthone were more similar to the diffusion-limited kinetics.