Weekly+Lecture+Summary+LSF

__Week 1__ This week introduce about the physical properties of food.What is the physical properties of food?Physical properties of food is study the properties of food. It is important to appreciate that physical properties such as colour, texture, flow behaviour, surface property, phase transition (e.g., crystallization) are important parameters to consider, together with the chemical properties and reactions in food systems. Some examples of the applications of physical properties of food in food processing, formulation and product development.

__Week 2__

What is rheology?The subject rheology is concerned with the study of deformation and flow of matter.Rheology aim at measuring those properties of material that control their deformation and flow behaviour when subjected to external force.The example of external force are spreadind,spraying, kneading and so on.When subjected to external forces, solids will deform whereas liquids will flow.We encounter the rheology in our daily life.For example, we pouring tomato sauce into plate or we kneading the toothpaste.



__Week 3__ This week still study about the rhelogy of food but in the part of stress and strain.We all deal stress and strain in our daily lives,but the way food materials respond to stress and strain impacts in processing,appearance and most importantly texture.Strain in the context of rheology is simply a quantitative measure of the extent to which an element of material has been deformed.We know that deformation implies a change of shape.Stress is simply defined as a force per unit area.Thus, rheology is mainly concerned with the relationship between strain, stress, and timeS strain and stress are related to deformation and force, respectively. Strain accounts for the size effect on material deformation due to difference in length (or height) of specimens, whereas stress accounts for the size effect on applied force due to difference in cross-sectional area of specimens. Using strain and stress, rheologists are able to obtain true material properties independent of the sample size and geometry, and compare results for sample of different sizes and geometries

__Week 4__ This week we study about the newtonian and non-newtonian fluid and also shear rate.Newtonian flow which is classified as newtonian is characteristed by a viscosity which is independent of the shear rate.Example of newtonian fluid include water, mineral, various syrup,honey, milk ,fruit juices and wine.Non-newtonian is dependent on shear rate.Non-newtonian can be either time independent or time dependent.The term 'independent' and 'dependent' refer to the effect that shearing energy input has on the viscosity of a fluid as it is being sheared.For time independent system,viscosity chsnges as shear rate is changed. For time independent syatem, the viscosity changes with time under a constant shear rate.Time independent, non -newtonian flow includes pseudoplastic,bingham plastic and dilatant plastic.Non-newtonian flow in time dependant are thixotropic fluid.Time independent and time dependent both exhibit shear thining behaviour.Pseudoplastic are fluids which decrease in viscosity as shear rate increase.This type of flow bwhaviour is reversible and known as shear thining.Example of psedoplastic fluid is emulsion and dispersion.The example of bingham plastic are tomato ketchup,mayonnaise and topping.For dilatant,its viscosity increases with increasing speed.It described as shear thickening.For thixotropic fluid,it viscosity is measured from low to high shear rate then back to low shear rate,and the viscoties coming down are lower than those going up.These fluid loss viscosity under constant shear.Example are tomato paste and apple sauce.

__Week 5__ This week study about viscpelastic material and deborah number.Some foods are solid, such as hard cheese, hard candy, or even an ice cube. What about foods such as jelly, bread, cakes, dough, noodle, tofu, soft cheese, etc.? These are materials which have some solid-like and some liquid-like properties – or we call them “viscoelastic materials”.Viscoelastic materials are both elastic (having solid-like) and viscous (having liquid-like). Their rheological properties depend on the relative degrees of elasticity and viscosity and are also dependent on the time-scale of the deformation.Deborah number is defined as the ratio between a characteristic time of the material and a characteristic time of deformation process,which is taken as the experimental time scale.The time of the deformation process is the stress relaxation time.We also learn the measurement of texture.Viscoelastic properties are measured by using a rheometer. The test is known as small-amplitude oscillatory tests (SAOS). SAOS measurements enable quantification of elastic and viscous components of a material simultaneously. Basically, a small oscillation (sinusoidal) stress (or strain) is applied on the sample and the respective deformation and the phase relationship between viscous and elastic components is measured. This is non-destructive test, i.e., the structure of the material is not destroyed during the test. The stress and the strain is very small, just sufficient to measure the viscoelastic properties of the material.

rheometer

__Week 6__ This week study about food texture measurement.Texture is such an important physical attribute of food. In fact, when assessing the overall organoleptic quality of a food, texture must be considered together with flavor and appearance.Texture measurements are based on stress-strain relationships or rheological properties.Texture instruments have been classified as measuring force,distance,time and energy.They may also measure ratios of these variables or measure in multiple units.Texture instruments have application in the areas of product development,product substitution and quality control.

__Week 7__

This week learn about the emulsion and surface tension.A dispersion or suspension of liquid droplet in a liquid continuous phase is called an emulsion.An emulsion consists of two immiscible liquid (oil and water),with one of the liquids dispersed as small spherical droplets in the other.There are two type of emulsion that are water in oil (w/o):butter and margerine.The second type are oil in water (o/w): mayonnaise,salad dressing,milkand sauces.Surface tension is defined as the force acting over the surface of the liquid per unit length of the surface perpendicular to thye force.Surface tension is the property of a liquid in contact with air that makes it behave as if it was covered with a thin membrane under tension.Molecule inside the liquid interact equally with other molecule,from allsides, whereas the molecule at the surface is affected only by the molecule below it. The molecules exposed to air behave differently and try to contract to the smallest possible ares.



spider can walk on the surface of water is due to surface tension

__Week 8__ This week learn about the foam.A foam is a coarse dispersion of gas bubbles in a liquid (or solid) continuous phase. Some of the foods we eat are foam, or prepared from foam! Ice cream, bread, marshmallow – these are examples of food foams. In the process of preparation, many food products are mixed or beaten and bubbles of gas are dispersed in them. Food foams (aerated foods) may be classified according to food type, history, aeration process, air content, rheology, stability or stabilization mechanism .A bubbly foam is formed when the amount of gas incorporated is low enough for bubbles to retain roughly spherical shape.

foam form when pour beer to glass