A reverse engineering approach to sucrose replacement in biscuits: modelling texture

肥胖、2型糖尿病和冠状动脉疾病等慢性非传染性疾病的全球增加与高糖摄入和过度消耗能量有关。在英国，添加糖的主要饮食来源是软饮料、面包店和糖果产品。饼干的含糖量约为30-40%，是一种多功能产品，受到所有消费群体，尤其是儿童的欢迎。出于对日益增长的儿童肥胖率的担忧，以及为了帮助人们遵循更健康的生活方式，英国政府出台了一项政策，限制高脂肪、高糖和高盐产品（HSFF）的位置和店内促销。这促使食品行业在产品配方方面做出进一步努力。然而，在饼干等烘焙产品中，用更健康的替代品替代蔗糖被证明是具有挑战性的，因为蔗糖除了提供甜味外，还发挥着多种功能。在过去的几十年里，研究主要集中在测试作为糖替代品的成分（多元醇、低聚果糖和菊粉、麦芽糊精、聚葡萄糖等）和评估对饼干质量的影响。最近，一个关于蔗糖、水和生物聚合物（面筋和淀粉）如何在面团和饼干系统中热力学相互作用的新理论被提出，定义了塑化和吸湿性能；决定饼干物理和感官结构特性的主要参数。蔗糖在混合和烘烤过程中被溶解，然后在烘烤过程中形成过饱和溶液（橡胶状态），最后在冷却和储存过程中蔗糖可能再结晶4。烘焙过程中的糖浓度也影响支链淀粉的玻璃化转变温度和淀粉糊化过程。因此，需要进一步了解饼干加工过程中决定碳水化合物转变（熔化、再结晶、糊化）的因素和参数，以便全面了解饼干系统中的热力学变化，以及这些变化如何决定饼干的物理和感官质地特性。本研究的假设是，饼干系统（糖-水-生物聚合物）在加工过程中发生的热力学和动力学变化可以建模，以设计新的蔗糖替代品和重新配方策略，以减少蔗糖，同时达到目标的质地特性。研究目标是：1)评价用蔗糖或蔗糖替代品（多元醇、稀有糖、其他碳水化合物）制作的饼干在混合、烘烤和储存过程中的热力学过程（玻璃化转变和结晶现象）和动力学变化（水扩散）(调制差示扫描量热法；2)利用超小角x射线散射（USAXS）和衍射表征从初始混合到最终产物从分子到微米长度尺度的结构演变。3)评估面团和饼干样品的物理性质（流变仪、质地分析仪、尺寸、x射线断层扫描）。4)分析饼干的口感（口腔加工和描述性定性方法）和甜度（体外和体内糖扩散）的感官知觉。将评估感知和仪器结果之间的相关性。5)利用量子化学模型和经典分子动力学计算蔗糖替代品在单分子、中小簇和体水平上的物理和物相性质。6)通过关联蔗糖替代品的属性（目标1）、纹理相空间（目标2）和纹理描述符（目标3和4），创建定量结构活性关系（qsar）。QSAR模型将被开发和测试，以预测饼干的物理和感官纹理特性。

The global rise in chronic non-communicable diseases such as obesity, type 2 diabetes, and coronary disease has been linked to high intake of sugar and excessive energy consumption. The main dietary source of added sugars in UK are soft drinks, bakery and confectionery products. Biscuits, with around 30-40% sugar content, are versatile products and popular among all consumer groups, particularly children. Owning to concern over increasing childhood obesity rates and with the aim to help people follow a healthier lifestyle a UK Government policy has come into force1 restricting the location and in-store promotion of high fat, sugar, and salt products (HSFF). This has driven further efforts from the food industry in product reformulation. However, the replacement of sucrose with healthier alternatives in bakery products such as biscuits has been proven challenging due to the multifunctional role that sucrose plays, in addition to providing sweetness2. During the last decades research has focused on testing ingredients as sugar replacers (polyols, oligofructose and inulin, maltodextrins, polydextrose,etc) and assessing the effect on biscuit quality. Recently a new theory on how sucrose, water and biopolymers (gluten and starch) interact thermodynamically in dough and biscuit systems has been proposed defining the plasticising and hygroscopic properties; the main parameters that determine physical and sensorial textural properties of biscuits3. Sucrose gets solubilised during mixing and baking, then a supersaturated solution (rubbery state) is formed during baking and finally sucrose may recrystallise during cooling and storage4. Sugar concentration during baking also impacts amylopectin glass transition temperature and starch gelatinisation process. Therefore, a further understanding on the factors and parameters that define carbohydrate transitions (melting, recrystallisation, gelatinisation) during processing of biscuits is needed for the development of a holistic picture of the thermodynamic changes in the biscuit systema and how these define the physical and sensorial textural properties of biscuits.The hypothesis of this study is that thermodynamic and kinetic changes in a biscuit system (sugar-water-biopolymer) that happen during processing could be modelled to design novel sucrose replacers and reformulation strategies to decrease sucrose while achieving targeted textural properties. The research objectives are: 1)To evaluate the thermodynamical processes (glass transition and crystallisation phenomena) and kinetic changes (water diffusion) during mixing, baking and storage of biscuits made with sucrose or sucrose replacers (polyols, rare sugars, other carbohydrates) (Modulated Differential Scanning Calorimetry, low field NMR)2)To characterise the evolution of the structures from initial mixing to final product from molecular to micron length scales using ultra small angle X-ray scattering (USAXS) and diffraction. 3)To assess physical properties of dough and biscuits samples (rheometer, texture analyser, dimensions, X-ray tomography). 4)To analyse the sensory perception of biscuits mouthfeel (oral processing and descriptive qualitative methods) and sweetness (in vitro and in vivo sugar diffusion). Correlations between perception and instrumental results will be assessed.5)To use both quantum chemical models and classical molecular dynamics to calculate physical and phase properties of sucrose replacers at the single molecule, small to medium cluster and bulk levels.6) To create a Quantitative Structure Activity Relationships (QSARs) by correlating sucrose replacers' properties (objective 1), texture phase space (objective 2) and textural descriptors (objective3 & 4), and). The QSAR models will be developed and tested to predict biscuit physical and sensorial textural properties.