Benders'dictionary of nutrition and food technology

411citriol (vitamin d) and thyroid hormone and other nuclearactinghormone receptors.retinol binding protein (1) Plasma protein (RBP) required fortransport of retinol; synthesis falls in protein–energy malnutritionand zinc deficiency, leading to functional vitamin a deficiencydespite adequate liver reserves. Because apo-retinolbinding protein does not occur in plasma, measurement of RBPprovides a sensitive index of vitamin A status.See also relative dose response test; transthyretin.(2) Cellular retinol (and retinoic acid) binding proteins(CRBP and CRABP) are essential for uptake of retinol andretinoic acid into cells, before onward metabolism and bindingto retinoid receptors.retinol equivalents See vitamin a.retort In food technology, an autoclave.retort pouches Laminated plastic or plastic and metal film packagingfor ambient-stable foods that are cooked in the factoryand then reheated in the pouch at home.retrogradation Cooked starch has an amorphous structure; thestaling of bread and other starchy foods is due to crystallisationof the starch, so that crumb loses its softness, a process that canbe delayed by addition of emulsifiers (crumb softeners) such aspolyoxyethylene and fatty acid monoglycerides. A number ofmodified starches (see starch, modified) are used to slow theprocess of retrogradation.retroretinol Isomer of retinol (see vitamin a); one of the physiologicallyactive retinoids.retrovirus RNA-containing virus that can incorporate its geneticmaterial into the DNA of a host cell by making a DNA copy ofthe RNA using reverse transcriptase.reverse osmosis See osmosis, reverse.reverse transcriptase Enzyme (EC 2.7.7.49) encoded by RNAviruses that catalyses the synthesis of dna from an RNA template(the reverse of the process that occurs in transcription).This permits incorporation of a copy of the virus genome intothe host DNA. Reverse transcriptase is widely used in molecularbiology and biotechnology to insert novel genes derived frommRNA into plasmids.Reynolds number (Re) Used to categorise fluid flow = (diameterof pipe × average velocity × fluid density)/fluid viscosity.A value4000 is turbulent.RF heating See microwave cooking.rhamnose A methylated pentose; 33% as sweet as sucrose; widelydistributed in plant foods.rheology The science of the deformation and flow of materials.