面向鲜莲子去心的莲仁物理与力学特性

为揭示莲仁浸泡时间对鲜莲子去心质量的影响规律,该研究开展不同浸泡时间下莲仁的物理与力学特性研究。首先分析了莲仁、莲心几何参数随浸泡时间的变化规律;测定了不同浸泡时间下莲仁的硬度、弹性模量、抗压强度和去心力等力学特性,获得了莲仁材料的应力-应变与载荷-位移曲线;采用回归分析方法建立了莲仁物理和力学特性指标与莲仁浸泡时间的对应关系。研究结果表明,莲仁最大短径、长度、尖端裂口长度与最大宽度,莲心长度、根部直径、最大厚度与最大宽度数值均随浸泡时间的增大而增大;莲仁硬度、弹性模量、抗压强度与去心力则随莲仁浸泡时间的增加而降低。其次,基于研制的鲜莲子空气挤出去心机开展了不同浸泡时间下莲仁的去心试验,研究发现,莲仁浸泡时间对通心率、莲仁破损率和莲心完整率有直接影响。当莲仁浸泡时间较短时,通心率和莲心完整率较低,莲仁破损率较高;而随着浸泡时间的增加,通心率和莲心完整率随之增加,莲仁破损率则降低,但浸泡时间过长,破损率又会增加。当浸泡时间为120 min,莲仁含水率为63.08%时,可获得较佳去心效果,通心率为94.67%,莲心完整率为84.00%,莲仁破损率为3.33%。研究结果可为提高鲜莲子去心加工质量、揭示鲜莲子高效低损伤去心机理提供基础数据支撑。

Physical and mechanical properties of lotus kernel for plumule removal of fresh lotus seeds

This study aims to reveal the effect of the soaking time of the lotus kernel on the quality of the plumule removal in the fresh lotus seeds. The physical and mechanical properties of the lotus kernel were investigated under different soaking times. The "Taikong 36" variety lotus seed was chosen as the research object. Firstly, a series of experiments were carried out to establish the relationship between soaking time and moisture content of the lotus kernel. The moisture contents of the lotus kernel at soaking times of 0-180 mins were obtained as 60.75%, 62.06%, 62.54%, 62.85%, 63.08%, 63.23%, and 63.45%, respectively. Secondly, the geometric parameters of the lotus kernel and lotus plumules under different soaking times were measured using an vernier caliper. It was found that the maximum short diameter and length of the lotus kernel, and the length and the maximum width of the pointed fissure at the kernel tip increased with an increasing soaking time, as did the length, root diameter, maximum thickness, and maximum width of the lotus plumule. Thirdly, the hardness of the lotus kernel under different soaking times was measured using a Universal TA texture analyzer. The results showed that their hardness gradually decreased, as the soaking time of the lotus kernel increased. Once the soaking time increased from 0 to 180 min, the hardness of the lotus kernel decreased from 8.76 to 7.83 N. Mechanical properties tests of lotus kernel under different soaking times (including elastic modulus test, compressive strength test, and the force measurement for removing lotus plumule) were conducted using the UTS-4.5KN/T162 universal testing system, in order to obtain the stress-strain curve and load-displacement curve of the lotus kernel material. The relationship between physical and mechanical performance indicators of lotus kernels and their soaking time was established using regression analysis. It was found that the elastic modulus, compressive strength of the lotus kernel, and the force of removing lotus plumules decreased with the increase of soaking time. Once the soaking time increased from 0 to 180 min, the longitudinal compressive modulus of lotus kernel decreased from 5.44 to 5.01 MPa, while the compressive strength decreased from 5.15 to 4.75 MPa, the lateral compressive modulus of lotus kernel decreased from 4.48 to 3.74 MPa, and the compressive strength decreased from 4.07 to 3.54 MPa, the force of removing the lotus plumules using a solid punch needle decreased from 18.26 to 16.16 N, and the force of removing the lotus plumules using a hollow punch needle decreased from 14.54 to 12.31 N. Finally, the air extrusion plumule-removing machine of fresh lotus seed was developed to conduct the plumule-removing experiment of lotus kernel with different soaking times. It was found that the soaking time of the lotus kernel had a direct impact on the plumule complete removal rate, kernel breakage rate, and plumule intactness rate. When the soaking time for the lotus kernel was relatively short, there was also the smaller length and width of the fissure at the tip of the lotus kernel, indicating that the lotus plumules could not squeeze out of the compressed air. The lotus kernel presented the higher hardness, elasticity modulus, compressive strength, and the force of removing the plumule, which can easily cause the breakage of the lotus kernel and plumule. Therefore, the plumule complete removal rate and the plumule intactness rate of the lotus kernel were lower, resulting in a higher lotus kernel breakage rate. The length and width of the fissure at the tip of the lotus kernel also increased, as the soaking time increased. The hardness of the lotus kernel, elastic modulus, compressive strength, and the force of removing the plumule decrease with the increase in soaking time, making it easier for the lotus plumule and lotus kernel to completely separate. Furthermore, the lotus kernel breakage rate remained relatively low with the increase in the plumule complete removal rate and plumule intactness rate. If the soaking time was too long, there was an increase in the moisture content, the breakage rate, as well as the length and width of the fissure at the tip of the lotus kernel, as the soaking time increased. Although compressed air can easily extrude the lotus plumule for the higher plumule complete removal rate, the hardness, elastic modulus, compressive strength, and force of removing the lotus plumule continued to decrease, with the increase in soaking time. The breakage of the lotus kernel and plumule was easily caused by the cracking at the interface between the lotus kernel and embryo, thus increasing the lotus kernel breakage rate with the low intactness rate of the lotus plumule. The optimal removing plumule of lotus kernel can be achieved when the soaking time was 120 mins (the plumule complete removal rate was 94.67%, the plumule intactness rate was 84.00%, and the lotus kernel breakage rate was 3.33%). The finding can provide the basic data support to improve the lotus kernel quality in the efficient and low-damage removal processing of plumule in fresh lotus seeds.