CAJ | 학술논문

旨在建立冷冻浓缩过程冰晶生长的数理模型，用以微观上分析冰晶夹带造成液态食品中溶质损失的问题。探讨结晶时间对冰晶形貌的影响。采用国内外描述相变微观结构的相场模型，将液态食品体系视为水和溶质二元结构，模拟冰晶生长的演变过程。研究等温结晶情况下，计算时间对冰晶生长形貌的影响及其对冰晶内部溶质浓度分布的影响。模拟结果表明，随着时间的延长，冰晶形貌逐渐变大，主干变细，二次分枝乃至三次分枝更加发达；同时，冰晶所包含的溶质浓度越大，各区域的溶质浓度分布也随之改变。由于溶质再分配，冰晶溶质分布曲线存在着波峰与波谷，波峰对应着来不及扩散溶质的冰晶尖端，波谷对应着冰晶固相。结果启示，在等温情况适当控制结晶时间将有效控制冷冻浓缩过程冰晶的形貌演化，降低液态食品冷冻浓缩过程的溶质损失。为进一步研究各种因素对冰晶生长的影响提供理论依据，从而为改进冷冻浓缩工艺、推进其工业化提供技术支持。
지재건립냉동농축과정빙정생장적수리모형，용이미관상분석빙정협대조성액태식품중용질손실적문제。탐토결정시간대빙정형모적영향。채용국내외묘술상변미관결구적상장모형，장액태식품체계시위수화용질이원결구，모의빙정생장적연변과정。연구등온결정정황하，계산시간대빙정생장형모적영향급기대빙정내부용질농도분포적영향。모의결과표명，수착시간적연장，빙정형모축점변대，주간변세，이차분지내지삼차분지경가발체；동시，빙정소포함적용질농도월대，각구역적용질농도분포야수지개변。유우용질재분배，빙정용질분포곡선존재착파봉여파곡，파봉대응착래불급확산용질적빙정첨단，파곡대응착빙정고상。결과계시，재등온정황괄당공제결정시간장유효공제냉동농축과정빙정적형모연화，강저액태식품냉동농축과정적용질손실。위진일보연구각충인소대빙정생장적영향제공이론의거，종이위개진냉동농축공예、추진기공업화제공기술지지。
The quality of products produced through freeze concentration is better than that produced through evaporation concentration and has lower energy consumed. But freeze concentration has been limited for industrial production because of the loss of soluble solids caused by ice crystal entrainment. Reducing the ice crystal entrainment and losses is critical for industrial production of freeze concentration. The breakthrough is to control ice crystal growth behavior. In order to develop a freeze concentration process mathematical model for simulating the evolution of ice crystal growth from the microscopic structure, through regarding liquid food as water and solute in binary system, the phase-field model theory was applied, liquid food system was treated as water and solute in binary system. The effects of ice crystal growth and solute concentration distribution over crystallized time were studied. Results showed that the crystallized time could affect the growth of lateral branch. Ice crystal growed gradually when the main branch become thinner and the secondary dendritic arms were well-developed. Solute field and phase field profiles were consistent. The solute concentration of ice crystals contained was greater, and the regional solute concentration distribution also changed. The precipitatied solute by crystallization was not completely dissoluted into the liquid phase since the solute diffusion velocity was much less than the ice crystal growth rate. The solute concentrated on the ice front of solid liquid interface. The solute concentration distribution was different in different parts of the solid-liquid interface. The solute concentration between crystal branches was the highest since the well-developed lateral dendritic branch captured the partion of the solute. The solute of lateral interface of ice crystals was enriched. The speed in the lateral ice crystals was slower than in the tip of ice crystals, which caused not sufficiently diffusion of the solute in lateral crystals. The solute concentration of ice crystals on cutting-edge solid-liquid interface showed the peaks and troughs by the solute redistribution. The solute concentration peak was formed because the growth rate of ice crystal tips was quickly enough to fully diffuse the solute. The trough corresponded to the ice crystal’s solid phase. The simulation results were consistent with the experiment observation. The entrainment rate of ice crystals increased when the freeze concentrated time reached at a certain time. The entrainment rate of ice crystal could be reduced with properly controlling the crystallized time during freeze concentration process. In this study, we ignored the latent heat released and used an isothermal simulation. The simulation system was treated as dual components with water and solute. The influencing factors such as cooling rate, convection, super-cooling degree need to be further investigated. The non-isothermal algorithm and multiple structure of liquid food also need to be considered in the future research.