Benders'dictionary of nutrition and food technology

244humidity, absolute (or specific) The water vapour content ofmoist air, usually expressed on a dry-weight basis, e.g. kilogramsof water vapour per kilogram of dry air. Sometimes expressedon a volume basis, e.g. kilograms of water vapour per cubic metreof dry air.humid volume The volume of moist air containing unit mass ofdry air at a pressure of one atmosphere and a specifiedtemperature.hummus Middle Eastern hors d’oeuvre; a purée of chickpeas andtahini with garlic, oil and lemon juice.humulones Bitter aromatic acids (humulone, cohumulone andadhumulone) in hops, used to flavour and preserve beer. Convertedto isohumulones during boiling of the wort. Also knownas α-acids, to distinguish them from the lupulones (β-acids).hurdle technology The concept of mild but effective food preservationbased on considering all the different factors that inhibit(or act as hurdles to) the growth of spoilage organisms.hursting mill Horizontal stone grinders formerly used for grainmilling.husk (or hull) The outer woody cellulose covering of seeds andgrains. In wheat it is loosely attached and removed during threshing;in rice it is firmly attached. High in fibre content and oflimited use as animal feed.HVP Hydrolysed vegetable protein; used as a flavour enhancer.hyaluronidase Enzyme that catalyses random cleavage of 1,4links (EC 3.2.1.35) or 1,3 links (EC 3.2.1.36) between glucuronicacid and N-acetylglucosamine in hyaluronic acid. Injected underthe skin of poultry before slaughter to enhance tenderness andflavour.See also tenderisers.hydrocooling Vegetables are washed in cold water, then subjectedto vacuum while still wet. The evaporation of the waterchills the vegetables for transport. Also applied to vegetableswashed in ice-water without vacuum treatment.hydrodyne process Method of tenderising meat in which it is subjectedto supersonic shock waves generated under water by asmall explosive charge to shatter the fibres without affecting itsother properties; faster than other methods.hydrogen Formed in small amounts by intestinal bacterial fermentation;measurement of exhaled hydrogen on the breath providesa sensitive way of diagnosing disaccharide intolerance.hydrogenation Conversion of liquid oils to semi-hard fats by theaddition of hydrogen across carbon–carbon double bonds; usedfor margarines and shortenings intended for bakery products.See fatty acids, unsaturated.