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ADVANCED FOOD ANALYSIS 4 - Coggle Diagram

- - - - immersion in the liquid--> used to extract non-volatile/semi volatile compounds that do not readily travel into the gas phase
        
        The amount of analyte is proportionated to its concentration in sample matrix (C0 ) and to
        its distribution constant (Kes ) according to the following equation n= KVC--> The latter indicates that extracted analyte amount is independent by sample volume
        used.
        
        The extraction time represents a critical
        step in the SPME technique. If the main goal is high throughput probably the shortest
        extraction time is best way
        
        Under that condition
        the uptake of analyte onto the fiber
        remains constant. Temperature, ionic
        strength and pH affect the extraction
        
        Sample modification--> pH: sensitivity of SPME is maximum when extracting neutral analytes not disassociated. in case of acidic analytes select a pH lower the pKa of the compounds (about 2 units)
        • in case of basic analytes select a pH higher than pKa (about 2 units).
        
        Ionic strength: Adding salt to an aqueous solution minimizes the variability in ionic
        strength in the sample, since the salt, the increase of ionic strength could affect the volatility of some compounds and could
        cause the extraction of matrix interferences
        
        Dilution: In case of complex matrix, sample dilution could improve the extraction of
        analytes. Temperature: The increase of temperature lead to increase of analyte diffusion
        coefficient, HS capacity, extraction rate as well as speed
        
        fibers--> non polar fibers Polydimethylsiloxane (PDMS) is the
        standard choice. Polar Fibers: Coatings like Polyacrylate and Carbowaxdivinylbenzene (CW-DVB) are tailored for polar analytes. Common commercial phases include singlecoatings or blended combinations to
        expand extraction capability
        
        Desorption--> Typically, the fiber should be desorbed at high temperature to ensure the immediate release of the volatile analytes. . In
        general in GC, the initial oven temperature of oven GC is low (40-50 °C) to allow
        refocussing of the semi and less volatile analytes at the column entrance.
        
        GC Chromatogram: Represents the final
        analytical output. After the compounds are thermally desorbed from the SPME fiber into the gas chromatograph, they are separated and detected
        
        1 more item...
        
        Non-bonded: Stable in aqueous solutions,
        but must not be used with non-polar
        organic solvents to prevent coating
        damage. Bonded: Chemically cross-linked, making
        them stable and compatible with all organic
        solvents.
- - - - light penetrates the sample and interacts with its chemical constituent before exiting random angles--> particle size and shape affect hoe light penetrates and leaves the surface
      - different parts of a food sample can absorb the same types of light, instead scientist use a computer-math method called chemometrics--> test a food group--> scannering with infrared--> computer matched and create a particular formula
        
        Fixing Overcrowded Data and Sorting Foods. Sometimes, giving the computer too much light data causes a problem called overfitting
        
        To fix this, scientists use "data compression" methods (like PLS or PCR) to shrink a massive cloud of complex light data into just a few clean, unique pieces of information--> this technology is also used to classify foods rather than just measure them
        
        key insights--> approved by AACC international to measure protein in various grains, important for the quality of red meats, used for misurazion of butter moisure, applied to monitor total sugars/soluble solids in fruits, vegetables, and juices, as well as sucrose and lactose in chocolate and corn sweeteners. Shows strong potential for tracking chemical changes during storage/processing and directly predicting the end-use quality and processing traits of commodities.