Summary Effect of heat and pH on colour and texture of green vegetables
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Course
Year 1 Term 1 Food Products
Institution
Hogeschool Van Hall Larenstein (VHL)
Summary of Effect of heat and pH on colour and texture of green vegetables year 1 term 1 of Food Technology.
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effect of heat and ph on colour and texture of green vegetables
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Hogeschool Van Hall Larenstein (VHL)
Food Technology
Year 1 Term 1 Food Products
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Effect of heat and pH on colour and texture of green beans
Heating can release organic acids → reaction acids with chlorophyll → Mg-atom replaced
with H-atom → Olive green pigment Pheophytin
Heating in alkaline solution → replacement methyl alcohol and phytyl alcohol groups by Na-
ions → bright green pigment Chlorophyll
Removal from phytyl alcohol → Chlorophyllin water soluble → leakage from vegetable in
solution
Effect heating on texture → Function hemicellulose
Hemicellulose is een verzamelnaam voor een reeks zeer nauw verwante koolhydraten die
worden gemaakt in planten. Hemicellulose is een belangrijke component van de celwand en
vormt meestal een soort matrix waarin cellulosemoleculen ingebed liggen.
Cell = basic structural unit of all plant tissues → surrounded by cell walls that provide
an elastic support for retaining the contents of the cell.
Cell membrane layer → located just inside cell wand, controls the passage of liquids
into and out of the cell.
Cell = filled with cytoplasm (jelly-like substance) composed of: protein, sugars, salts
& other substances dispersed in water.
Plastids (separate inclusion bodies, 4-10 nm in diameter) located in cytoplasm →
contain pigment chlorophyll
Mature cells contain vacuoles → separate compartments filled cell sap (fluid)
composed of: sugars, salts, organic acids pigments and other materials.
Green vegetables contain green pigment chlorophyll → plays key role in transferring
light energy to chemical energy during the growth & development of the plant by the
process of photosynthesis.
Altered forms Chlorophyll → Pheophytin & Chlorophyllin
Vegetable processing
Thermal processing or canning → most common commercial method of preservation.
Process: vegetables → cleaned → trimmed → cut → packed into cans → sealed → heated
to sufficiently high temperatures (240⁰F) to destroy micro-organisms that cause spoilage &
disease.
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