Benders'dictionary of nutrition and food technology

309micronutrients vitamins and minerals, which are needed in verysmall amounts (µg or mg per day), as distinct from fats, carbohydratesand proteins which are macronutrients, needed in considerablygreater amounts.micro-organisms Bacteria, yeasts and moulds; can cause foodspoilage, and disease (pathogens); used to process and preservefood by fermentation and have been used as foodstuffs (singlecell protein and mycoprotein).See also food poisoning.microscope, atomic force Microscope in which the surface of thespecimen is scanned by a sharp probe that is repulsed away fromthe surface by atomic forces; measuring the deflection of theprobe permits the production of a detailed topographical map ofthe sample at the molecular level.microscope, confocal Microscope in which a point light source(commonly from a laser) is focused on a small region of thesample, so that only the in-focus plane is illuminated, with theout of focus regions appearing as a black background.microscope, electron Microscope using a focused electron beamrather than light; permits resolution of the order of 0.2nm, comparedwith light microscopy with a resolution of 0.25 µm. In scanningelectron microscopy the electron beam is reflected from thesurface of the sample; in transmission electron microscopy it istransmitted through the sample.microvilli Hair-like projections (∼5µm long) from the surfaceof epithelial cells, e.g. in the gastrointestinal tract. Whenmicrovilli form a dense covering on the surface of a cell, this isthe brush border.microwave cooking Rapid heating by passing high-frequencyelectromagnetic waves (commonly 2450 MHz, sometimes896 MHz in Europe and 915 MHz in the USA) from a magnetronthrough the food or liquid to be heated. The process is based onthe electric dipole produced by the negatively charged oxygenatom and the positively charged hydrogen atoms in water. Theapplication of a rapidly oscillating electric field causes thedipoles to reorient with each change in the field direction, dissipatingenergy as heat. The ratio of the capacitance of the foodto the capacitance of air is the dielectric constant and dependson the number of dipoles, temperature and the changes inducedby the electric fields.middlings See wheatfeed.mid-upper-arm circumference (MUAC) A rapid way of assessingnutritional status, especially applicable to children.See also anthropometry; quac stick.migaki-nishin Japanese; mixture of dried fish fillets and abalone.