Introduction
Background on the Topic
Food engineering and material science is a relatively new thought process inclined towards the development and improvement of new products. It also helps build a keen understanding related to several mechanisms linked with the manufacturing of food and quality control purposes. Material sciences are well-developed studies in areas such as pharmaceutical materials and biotechnology. This approach is required for food systems to improve the shelf-life and quality of the products with the development of new processes and food products (Bhandari and Roos, 2012). Adequate basic science and engineering knowledge are required to apply materials science to the food system completely. Despite the fact that research activities on materials sciences are on-going in different sectors, no knowledge integration from various sectors of the filed as compiled. Food materials require reliability, safety, extended shelf life, and functional properties’ development. Consequently, the in-depth study of engineering and materials sciences will aid in fetching these outcomes.
As the functionality and quality of food products greatly rely on the components and properties, therefore, the structure requires having a strong design to attain the desired properties and qualities. Food materials engineering and science are also anticipated to add up to the development and significance of the advanced delivery system of nutrient with precise sensory, structural and nutrient releasing properties. The science of food materials has developed in line with the introduction and availability of technologies like Atomic Force Microscopy, Confocal Laser Microscopy, Electron Microscopy, Nuclear Magnetic Resonance spectroscopy, thermal analysis, and X-ray diffractometry. With the growth in food product quality and manufacturing, the fields under the scope of food materials science are developing (Bhandari and Roos, 2012).
Mechanism of Digestion
Digestions process is a complex and fascinating procedure. The intricate processes the food living beings consume turns it into energy and waste products. Digestion happens in the gastrointestinal tract which is a long tubular structure starting with the mouth and ending at the anus. The system propels the food forward, alters it with hormones and enzymes into usable particles which are absorbed in the body during the process. The timeframe required for food to travel from the mouth to the anus as waste is calculated to be around 30 to 40 hours.
The entry point of food is in the mouth. Salivary glands in the oral cavity produce saliva. Mastication (chewing) breaks the food into smaller particles; the chewing process makes it easier for salivary enzymes to attack the food. Once the chewed food enters the oesophagus, it is moved down to the stomach. Glands lining the stomach secrete enzymes and acid which aids in breaking down the food further. Then, the muscles in the stomach mix the food further. At the final phase of this process, broken down food is transformed into a thick creamy-textured fluid known as chyme.
Chyme is pushed into the first, shortest segment of the small intestine known as the duodenum. Here, with the help of the enzymes from liver bile and pancreas the broken down food is pushed to the small intestine. The small intestine is comprised of three segments. First being the duodenum, where food is broken down further. The next two segments of the small intestine (ileum and jejunum) are responsible for absorbing the nutrients from the processed material into the bloodstreams via intestinal walls. The leftover waste leaves the upper GI tract. Upper GI tract is basically made up of everything on top of the larger intestines. Finally, the waste travels further to the colon or large intestine (Balentine, 2018).
In-vitro Digestion Models to Evaluate the Digestibility
There are four main functions of the stomach, storing, mixing (with enzymes and juices), breaking food particles, and emptying it into the duodenum. The masticated food undergoes further digestion under the influence of the mechanical and biochemical processing of the stomach. Due to sphincter at the pyloric end of the stomach, the solid food particles having a size greater than 1mm retains back for further disintegration. The structure and composition of food particles greatly affect the digestive process. Food enriched in protein and fat takes longer time as compared to carbohydrates. An understanding of how the food is broken down into the human body is needed in order to deigned food that provides better, regulation, encapsulation of macronutrients and release of nutrients at the targeted place. To clearly understand the gastric process an invitro gastric model is required (Guo et al., 2014).
In vitro model is defined as a model composed of isolated components of an organism. In vitro gastric digestion, models are used to research and study the digestibility, structural changes to the food particles, and release of food particles under specific gastric conditions. The outcomes and results from the in vitro gastric models are often found to be faulty due to the higher complexity if achieving the chemical and physical and physiological properties and effects during the digestive simulation as compared to the events occurring in organisms (Hur et al., 2011).
Several different factors like mechanical and physical forces, enzyme activity, ionic composition, digestion time, characteristics of a sample, especially food components, possess great influence on the outcomes of invitro gastric models. In vivo model conditions can never be applied on in the vitro gastric model. In vitro models are designed to work with specific enzymes and single nutrients. The most important factor in in-vitro models is enzyme activity. Several enzymes characteristics like stability, pH, temperature, inhibitors, incubation period, concentration and activators have crucial significance in understanding the digestive process. The models and the objectives of the study in which in-vitro gastric model is designed to depend on the enzymes and incubation period. Single enzyme method can be helpful in the digestion of single components like protein, lipids, and carbohydrates.
As mentioned earlier, the characteristics of food along with the quantity and type of enzyme controls the digestion process. Increased in lipids and starch results in an increase in lipase and amylase. Similarly, an increase in the proteolytic enzyme is an indication of increased dietary protein. To truly simulate the gastric digestion process, enzyme composition, content and incubation time in the in-vitro gastric model is needed to be regulated accordingly (Hur et al., 2011). Different researches and studies have used in vitro gastric digestion model to find out the bioavailability, digestibility and structural changes to the organs and food particles during digestion; therefore the in vitro gastric models are useful tools analysis of drugs and food digestion.
Food Particle Size and Digestibility
According to Lundin et al., food structure and its impact on digestion, since the size of the food particle controls the digestive process, is the most emerging interest nowadays. Form tiny to bulk, from sub-atomic to atomic and from molecular to sub-molecular level food particles are composed of self-assembled or colloidal, independent and in emulsified structures. Despite the fact that atoms are the main building block of the food particles, the real starting point for the formation of matter is a collection of limited numbers of molecules. The molecular system of food, on the basis of the size of the molecules, is classified into three main types. Macro-structural, micro-structural, and nano-structural (Singh, Kaur and Singh, 2013).
Nanoparticles are as small as a nucleus. Before the formation of crystal, nanoparticles, also can be stated as the embryos of the matter, are just clusters of few molecules. As they grew tighter and together, they start to act like bulk matter. Nanoparticles simply fill the gap in between the atomic level and bulk molecular level of the matter. Having high Ven Dar Waal forces, and high magnetic properties and small nano size of these particles made them of key interest (Singh, Kaur and Singh, 2013).
The physical texture or simply the texture of the food depends on the macro structure that in turn controlled by the molecular level interaction of food components. The texture of the food has a greater significance on the sensorial characteristics of the food. Furthermore, the microstructure of the food plays an important role in providing and delivering the nutrients and in nutritional bioavailability, besides providing the textural characteristics to the food (Bhopatkar, Hamaker and Campanella, 2012). It is, therefore, necessary to understand the proper structuring of the food through micro to macro level scale. The food structure arse controlled by both interactions of food component and arrangement of the individual food particles. Structure of food is further classified as process generated food structure or native generated food structure. The state of food particles, crystalline, colloidal and amorphous, based on the composition of the food particle is responsible for the quality and ability to deliver nutrients.
The microstructure plays a crucial role in calculating the rate of digestion in different foods. The microstructure is extremely reliant on the processing, post-processing, and composition of the food. Two main factors that affect the digestive process are cell wall polymers and microstructure of the food particles. Physical texture of the food also helps in the absorption and digestion of the food (Singh, Kaur and Singh, 2013).
