Food Quality - Fundamental Concepts 2024 PDF

Food Quality Fundamental concepts Rosalind Deaker FOOD2000 Principles of Food Science  Learning outcomes By the end of this week you should be able to: – List parameters that define food quality and describe why these are important – Describe different types of meas...

Food Quality Fundamental concepts Rosalind Deaker FOOD2000 Principles of Food Science  Learning outcomes By the end of this week you should be able to: – List parameters that define food quality and describe why these are important – Describe different types of measurements and protocols used in the food industry to measure quality – Describe critical elements of analysis used for quality assessment and the importance of accuracy and precision  Overview of lectures Lecture 1 a) Definition of 'quality’? b) Quality parameters – visual and texture Lecture 2 a) Quality parameters - sensory b) Analytical approach – precision, accuracy and sources of error In FOOD2000 fresh produce is the context but principles are extendable to all foods What is ‘quality‘?  Terms and definitions Quality Suitability of a product for a specified purpose – judged against defined criteria Needs to be defined for each product Shelf life Period of time food is considered suitable for sale, use or consumption Food safety Free of harmful chemical, physical or biological contaminants Functionality Properties that contribute usefulness for a specific purpose e.g. dough strength, emulsifying agent, thickening agent  Importance of quality Quality is an important property of all foods and ingredients Consumer acceptability – sensory/organoleptic (flavour, texture etc.) Product consistency for both fresh consumption and processing (variability in raw materials unavoidable) Nutritional value Reducing waste, spoilage – meeting Drivers of food purchases specifications, maintaining quality over time International Food Information Council (ific.org) Trade (price and market share) – product differentiation Sensory properties of foods - highest importance for consumers  How is quality measured? Quality analyses may be… – Subjective – appearance (visual), texture and flavour – Objective – physical/physicochemical (e.g. texture), spectroscopic (e.g. colour), chemical/biochemical (e.g. nutritional), biological (e.g. microbiological), chromatographic (flavour volatiles) Relating the two is a big Quantitative, semi-quantitative and qualitative challenge in measures food science Traditional analytical, instrumental and sensory analyses Consumer acceptability is not easy to measure  Visual quality attributes The first quality attributes experienced by consumers Morphology (size, shape), appearance (colour, gloss, clarity, consistency) Physical defects (mechanical or pest injury, shrivelling/dehydration) Blemishes (physiological disorders, spoilage) Intermarché – Inglorious Fruit Campaign 2014 30% cheaper Importance of visual quality attributes Appearance has a halo effect that modifies subsequent perception of flavour and overall acceptability Consumers associate colour with other attributes, e.g., flavour, healthy nutrition, satisfaction  Visual quality attributes are used for differentiation or grading Average Very good Excellent Automated spectral and imaging technologies used in some industries to detect/reject on appearance attributes  Assessment of visual quality attributes Visual quality charts/specifications may be used to dictate limits of acceptability… Lentils Eg. Kimberley large cream chickpea - premium Desi chickpea  Colour charts are important in some industries Chiquita Banana Chart  Quantitative colour systems Many systems for quantifying colour – e.g. RGB, CMYK… CIE L*a*b* widely adopted for foods - designed to approximate human vision L* Lightness a* Red-Green b* Blue-Yellow ColorMeter RGB Other colour systems – Hunter Lab, Colorimeter for iPhone Munsell colour chart, spectrophotometry, $5 - 6 computer vision systems (pixels)  Texture Related to the rheological Liquids properties of food Newtonian eg. water, sugar – Elastic – (solid) can be syrup deformed and will return Non-Newtonian eg. to shape after stress cornstarch + water (shear – Viscous – (liquid) resistance to flow thickening), tomato sauce – Plastic – (solid) can be (shear thinning) moulded Foods are complex – don’t fit into one category e.g. viscoelasticity of dough  Textural quality attributes ISO definition - combination of mechanical, geometrical and surface attributes perceptible by mechanical, tactile, visual and auditory receptors Texture is experienced by: CRUNCH Finger tips - complex array of mechanoreceptors (mechanical resistance, surface topography, …) Lips - sense temperature and surface roughness Upper surface of tongue - very sensitive to detection of particle size (1-2 mm), shape, lubrication and friction Jaw and teeth - sensitive to mechanical attributes  More to mouthfeel than structure Consumers evaluate a lot of things about food texture during a short residence time in the mouth Stieger et al., 2013 Texture interacts with the way taste chemicals are released from food matrix Awareness of texture is often subconscious - when expectations are not met, the reaction may be strongly negative  Instrumental assessment of textural quality attributes Specialised instruments to measure textural attributes in specific food products Standardised compression patterns and accessories used to measure texture profiles  Instrumental assessment of texture Texture can be decomposed into measurements of resistance to force - compression tests eg. squeezing - shear tests eg. shearing through a food matrix - cut/break tests eg. applying force to cause a fracture - tensile strength tests eg. pulling a muffin apart - rheological (viscosity and shear) tests in fluid or semi-solid foods (eg. Brookfield viscometer) Texture analysis is complementary to physicochemical analyses eg. particle & bulk density, porosity, thermodynamic properties, chemical composition Texture analyser https://www.youtube.com/watch?v=DIGGcORgsas Descriptive terms for texture attributes Helps to translate properties to the consumer Descriptive terms for texture attributes Descriptive terms for texture attributes Source: Jowitt (1974)  Summary Quality parameters are specific to each product and related to intended use or purpose Quality parameters can be measured subjectively and objectively – may be qualitative, quantitative and semi-quantitative Colour and texture are both important sensory qualities - can also be measured using instruments