Optimization of salt morphology and oral perception of salt with CFD and CFD- DEM techniques

高钠摄入量是增加高血压和心血管疾病风险的主要因素之一。世界卫生组织（WHO）建议成年人每天的食盐摄取量不应超过5克。然而，在美国、英国和亚洲国家，盐的平均摄入量分别为12克、8.8克和9.4克/天。盐主要来自加工食品（75%），减少这些产品中NaCl的含量是改善公众健康的有效途径。然而，由于NaCl在控制发酵速率、防腐性能和增味方面的作用，降低其含量是困难的。在零食和其他加工食品中，盐可以增强味道，去除盐会改变消费者的认知和接受度，这在任何减盐策略中都应该考虑到。直接减少会影响消费者对咸味的感知，从长远来看，他们有可能会选择含盐量更高的替代产品，或者自己在自己喜欢的产品中添加盐。因此，食品工业寻求的策略是，用较低的盐量给消费者同样的咸感，如盐替代和盐颗粒的改性，以增加钠的可用性和溶解速度在唾液中。也有可能通过逐步减少所有食品中的钠含量来改变消费者的口味偏好，但这是不可行的，也不是对公众健康持续威胁的及时解决办法。近年来，一些替代品如氯化钾被用来代替食盐中的钠。然而，由于不受欢迎的金属和苦味，这种替代品有一些局限性。降低产品含盐量而不影响味道的更好方法是设计优化的盐颗粒，因为受体更快地溶解和吸收，因此可以更好地感知。表面积越大的盐晶体溶解得越快，从而产生更高的咸感。因此，具有较小尺寸或空心结构的晶体是首选。此外，非立方和凝聚晶体溶解更快，内部裂缝和空腔允许晶体在唾液b[1]中分解。Hurst等人（[5]）对不同的盐形态进行了测试，具有细颗粒、柔软的假球形结构、内部有空隙、表面积较大的SODA-LO盐具有最高的溶解速率和较短的被消费者感知的时间。Rios-Mera等人（bbb）和Galvao等人（bbb）分别在火鸡火腿和汉堡中使用了微粉盐晶体，并得出结论，在不影响味道的情况下，盐的摄入量可以减少多达30%。Freire等人的研究表明，使用更小的盐晶体可以使小穗马铃薯的这一比例达到50%。Chokumnoyporn et al.[9]和Moncada et al.[9]分别对烤花生和奶酪饼干得出了相同的结果。因此，设计出具有最大溶解速率和较低摄入量的新型盐颗粒是至关重要的。在这个项目中，我们的目标是通过高保真度的计算机模拟来设计优化的盐粒。首先，我们将从模拟不同形态的盐颗粒的溶解开始。在这个阶段，可以通过CFD模拟得到溶解曲线，并找到具有最大吸收和更高离子传输到受体的优化颗粒。然后，将更复杂的模型添加到模型的流动模式和口腔的静态几何。

High sodium consumption is one of the major factors in increasing the risk of high blood pressure and cardiovascular disease. The World Health Organization (WHO) recommends that adults should not consume more than 5 g/day NaCl [1]. However, in the US, UK, and Asian countries, the average intake of salt is 12, 8.8, and 9.4 g/day, respectively [2]. Salt is largely obtained from processed foods (75%), and decreasing the amount of NaCl in these products is an effective way to improve public health. Nevertheless, reducing NaCl content because of its role in controlling fermentation rate, preservative properties, and adding flavour is difficult [3]. In snacks and other processed foods, salt enhances the taste, and removing salt will change consumer perception and acceptance which should be considered in any salt reduction strategy.Direct reduction will affect the saltiness perception among consumers and, in the long run, there is a possibility that they will choose alternative products with higher salt content or add salt to their favourite product themselves [4]. Thus, food industries seek strategies that give the same saltiness perception to consumers with a lower amount of salt such as, salt substitution and modification of salt particles to increase sodium availability and dissolution rate in saliva. It may also bepossible to alter the taste preference of consumers by gradually reducing the sodium content of all food products which is not feasible and is not a timely solution for an ongoing threat to the public health. Recently, some replacers like potassium chloride are used in order to substitute sodium in salt [2]. However, due to the undesirable metallic and bitter flavour this replacement has some limitations.A better way of reducing the salt content of the product without compromising the taste is to design optimized salt particles that will be perceived better as a result of faster dissolution and absorption by the receptors. Salt crystals with higher surface area dissolve faster and lead to higher saltiness perception. Therefore, crystals with a smaller size or hollow structure are preferred. Furthermore, non-cubic and agglomerated crystals dissolve faster and internal cracks and cavities allow crystal disintegration in saliva [1]. Hurst et al. [5] tested different salt morphologies and SODA-LO salt with fine particles, soft pseudospherical structure with internal voids and higher surface area had the highest dissolution rate and lower time to be perceived by consumers. Rios-Mera et al. [6] and Galvao et al. [7] used micronized salt crystals in turkey ham and burgers, respectively and concluded that the salt consumption can be reduced by up to 30% without compromising the taste. Freire et al. [8] showed that for shoestring potato this can be reached up to 50% by using smaller salt crystals.Chokumnoyporn et al. [9] and Moncada et al. [10] obtained the same result for roasted peanuts and cheese crackers, respectively. Therefore, designing new salt particles with maximum dissolution rate and lower intake is of paramount importance.In this project, we aim to design optimised salt grains through high fidelity computer simulations. First, we will start by simulating the dissolution of salt particles with different morphologies. At this stage dissolution curves can be obtained using CFD simulation and optimized particles that have maximum absorption and higher transport of ions to the receptors will be found. Then, more complicated models will be added to model flow patterns and the static geometry of the oral cavity.