Modern trends in use of by-products in milk industry

Abstract

Skim milk has only a half energetic value of full milk and therefore it is a good raw material for production of a wide scope of dietetic milk products. Skim milk powder has been used in ice-cream industry, confectionery industry, bakery industry, for production of casein (rennet, acid and low viscosity), caseinates, glues etc. Utilization of whey, a by-product of the cheese manufacture, is a major problem of the dairy industry in Yugoslavia. Countries with the poor utilization of whey are severely affected by the water pollution due to whey disposal in water streams. Composition of whey include more than 50% of milk total solids and more than 20% of milk total nitrogen. Whey proteins are of very high nutritive value owing to the high content of essential amino acids. The nutritive value of whey proteins is even higher than egg-protein, usually referred as 100. Whey can be used in the production of many foods and feeds. Evaporated, concentrated whey can be used as a supplement in many industrial food products, such as bread and baked products, creams, meat and dairy products. Fermentation industries use whey as a raw material. The low protein content of whey in relation to lactose has hampered the problem of utilizing of whey as an animal feed supplement. The content of nonprotein nitrogen in whey can be substantially increased by the treatment with ammonia. This can be done by the introduction of anhydrous ammonia and thus neutralizing of whey during lactic acid fermentation. Fermented ammoniated condensed whey (FACW) is a product of a great importance for whey processing in order to obtain a product of increased content of digestible nitrogen. Ruminants are able to digest nonprotein nitrogen from the FACW.

Obrano mleko zbog manjeg sadržaja mlečne masti ima za 50% manju energetsku vrednost i zbog toga predstavlja dobru sirovinu za proizvodnju različitih vrsta dijetetskih mlečnih proizvoda. Obrano mleko u prahu koristi se u proizvodnji sladoleda, konditorskoj industriji, pekarskoj industriji, itd. Ono predstavlja osnovnu sirovinu za izradu kazeina (slatkog, kiselog, niskog viskoziteta), kazeinata, lepkova i dr. Iskorišćenje surutke stvara ogromne probleme u domaćoj industriji mleka, jer 80-90% od prerađenog mleka otpada na surutku, te se permanentno traže rešenja za njenu preradu u različite proizvode namenjene prehrambenoj i farmaceutskoj industriji. Hemijski sastav surutke zavisi od načina dobijanja, vrste mleka, tipa sira ili kazeina, načina izvođenja pojedinih tehnoloških operacija. Danas postoje različiti postupci prerade surutke kao što su: evaporacija, sušenje, elektrodijaliza, gelfiltracija, ultrafiltracija, koagulacija toplotom, fermentacija i hidroliza, obrazovanje koprecipitata i koagregata proteina mleka. Savremeni vid iskorišćenja surutke, namenjene za ishranu preživara, je proizvodnja amonijačne surutke kod koje je višestruko povećan sadržaj neproteinskog azota u obliku amonijum laktata, čija je biološka vrednost kao i kod proteina soje. Na području Mediterana, u Norveškoj i Severnoj Americi, od surutke se proizvode različiti albuminski sirevi kao što su Rikota, Manur, Misost, Sera, Brasi i Urda. Proizvodnja koprecipitata i koagregata proteina mleka je jedan od načina većeg iskorišćenja proteina surutke. Surutka dobijena u procesu izrade koprecipitata sadrži u najvećoj meri NPN i pogodna je sirovina za proizvodnju laktoze.