Effects Of Cryogenic Grinding On Flavor Composition And Odor Characteristics Of Spices

In this paper,cinnamon of cortex fiber,pepper of fruit and garlic of high humidity and high viscosity were used as raw materials to study the influence of cryogenic grinding on the composition characteristics of flavor substances of spices,and to explore the influence mechanism of the physical characteristics of spices and cryogenic grinding conditions on the wall breaking and extraction effect of spices.The main research contents and results are as follows:Firstly,the effects of cryogenic grinding on particle size distribution,morphology characteristics,contents of volatile oil and cinnamaldehyde,flavor composition and odor characteristics of cinnamon powder were studied.The results showed that the hardness and brittleness of cinnamon increased first and then decreased with the decrease of freezing temperature.The wall-breaking rate and specific surface area of cinnamon powder were increased by 1.19 and 1.22 times than at room temperature by cryogenic grinding,respectively.The contents of essential oil and cinnamaldehyde reached the highest at -35 ℃,which were 3.484%±0.02% and 181.43±4.52 μg/g.The contents of terpenes,aromatic hydrocarbons and alcohols increased,while the contents of aldehydes decreased slightly and the flavor richness was better.And the response value of sour taste,bitterness and bitter aftertaste increased.Furthermore,the contents of volatile oil and flavor changes of cinnamon were analyzed by two-phase aqueous extraction.Using the yield of volatile oil as the index,the optimal process was as follows: the mass fraction of ethanol 25%,the mass fraction of sodium dihydrogen phosphate 34%,the solid-liquid ratio 1:15 g/mL,the extraction time 60 min and the temperature of extraction 35 ℃.Under these conditions,the yield of essential oil and cinnamaldehyde were 2.82%±0.02% and 0.037%±0.001%,which were 1.07 and 1.31 times higher than that of conventional steam distillation,respectively.The volatile oil obtained by two-phase aqueous extraction contained more terpenes and retained the contents of long-chain alkanes,alcohols and aldehydes and ketones.Secondly,the effects of moisture content and grinding temperature on particle size distribution,morphology characteristics,contents of volatile oil and piperine,flavor composition and odor characteristics of pepper powder during cryogenic grinding were studied.The results showed that the hardness and brittleness of pepper increased first and then decreased with the increase of moisture content.The hardness of pepper increased with the decrease of freezing temperature,while the brittleness of pepper increased first and then decreased.After cryogenic grinding,the dispersion of pepper powder decreased,the wall breaking rate increased,and the contents of volatile oil and piperine increased to 1.14 times and 1.38 times of normal temperature grinding,respectively.The contents of the main terpenes in pepper flavor decreased with the increase of moisture content,increased first and then decreased with the decrease of grinding temperature,and enhanced the aroma intensity of alkanes and alcohols.Meanwhile,the total amount of flavor compounds in pepper oil was 1.41 times higher than that of conventional grinding materials,in which the contents of major terpenes and alcohols were increased and the odor intensity of methyl and aromatic organic sulfide was enhanced.Further,the eutectic solvent method was used to extract piperine from cryogenic ground pepper.The optimal parameters of choline chloride-citric acid system were as follows: the mole ratio 3:1,the content of water 25%,the solid-liquid ratio 1:50 g/mL and the extraction time 20 min,and the highest yield of piperine was 32.38±0.18 mg/g.Under the above extraction conditions,the yield of piperine increased with the reduction of grinding temperature and the increase of water content,and the maximum yield of piperine reached 45.38±0.54 mg/g at -40 ℃,which was 68.76% higher than that at room temperature.Thirdly,the effects of cryogenic grinding on garlic powder particle size distribution,morphology and structure,powder properties,contents of volatile oil and allicin,flavor composition and odor characteristics were studied.The results showed that the hardness and brittleness of garlic slices increased first and then decreased with the decrease of freezing temperature.The wall breaking rate and specific surface area of the garlic powder were increased,the settling rate,reclining angle and slip angle of the garlic powder were decreased,while the contents of volatile oil and allicin in the garlic powder were increased to 1.51 and 1.36 times of normal temperature grinding,respectively.After cryogenic grinding,the contents of alkanes and amides in garlic powder increased significantly and the odor intensity of nitrogen oxide,methyl and organic sulfide was enhanced.The contents of alkanes and ethers in garlic oil increased significantly,while the aldehydes decreased and the enrichment of benzene,ammonia,short-chain alkanes and sulfide was promoted.Finally,correlation analysis and structural equation model were used to study the influence mechanism of physical properties of spices and crushing conditions on wall breaking and extraction.The results showed that the stronger the hardness and brittleness of spices were,the higher the wall breaking rate and the extraction rate of active ingredients were.The higher the moisture content of the material,the stronger the hardness and brittleness of the mechanical properties of the material.With the increase of mechanical properties of materials and the decrease of grinding temperature,the effect of cryogenic grinding on material is enhanced.Therefore,by regulating the moisture content of materials,the mechanical properties of suitable grinding can be theoretically obtained,and by enhancing the mechanical properties of materials and reducing the grinding temperature,the particle size effect of cryogenic grinding can be theoretically obtained,which provides theoretical guidance for the intensive processing and utilization of spices.