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nitrogen in foods While pondering this question, I came across an article in the Manawatu Standard from 1885 entitled The Object of Eating. In this article it was stated: “we eat for warmth and strength; hence almost all articles of food have both these elements: have carbon to warm, and nitrogen to strengthen.” To the general public this statement still rings true today. We often hear about the need to “carbo load” (to ensure one has the energy to compete in a race) and one only has to wander down the health supplement aisles at the supermarket to see that there is clearly a public association between protein intake and strength. The reality is that the importance of nitrogen in foods is much wider than as a means of providing “strength”. There have been many advances in our understanding of the nutritional importance of nitrogen over the last hundred years, however, these will only be given cursory attention. Instead, this article focuses on how food technologists can utilize nitrogen containing compounds to design foods that achieve targets that may be set by nutritionists, consumers, marketers, legislators and food companies.
Nitrogen for health As noted in the opening paragraph, one of the key nutritional reasons for consuming nitrogen is for “strength”. The nitrogen consumed for this purpose has traditionally been in the form of proteins. Additionally, the proteins in turn have been consumed in a largely undifferentiated form such as “a steak”,“an egg”, or “a glass of milk”. However, the term “protein” covers a class of chemicals consisting of any combination of nitrogen containing amino acids in any number. Proteins between species and within a single species may have similarities but will have different amino acid compositions and therefore varying secondary and tertiary structures. Thus, consumers may consume a diet
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having an equivalent protein mass intake, but it does not necessarily follow that the physiological affect of the diet, protein-wise, will be equivalent. Recognition of this fact has led food technologists to develop processes to isolate specific proteins from the “raw food” at a commercial scale thus enabling new foods to be manufactured that maximize a particular benefit to the consumer. Going back to the “nitrogen for strength” idea and perusing the body building beverage aisles, one finds that the majority of formulations contain whey protein as the protein source and there is a good nutritional reason for this: branched chain amino acids are a significant component of muscles and the whey proteins in milk are a rich source of them. An athlete/body builder consuming undifferentiated “milk protein” would not observe the same rate of muscle growth as an athlete consuming only the whey protein fraction. Understanding the nutrition is really only one side of the equation – in order for this knowledge to have an impact on society foods must be designed that can deliver the desired outcome. In this case the specific form of protein must be available at commercial quantities.
nitrogen
Food technologists can utilize nitrogen containing compounds to design foods that achieve targets that may be set by nutritionists, consumers, marketers, legislators and food companies, writes Alistair Carr, Massey University. Why should we care about nitrogen in food?
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Isolating proteins The question then becomes: how does one manufacture these specific ingredients? In general, to isolate a protein – in this case the whey proteins from milk (which also contain fat, casein proteins, salts and lactose) – a food technologist must find a property of the component that is different to at least one of the other components. The property may be physical, such as size or density; or chemical, such as binding constants to charged surfaces. The next task is to create an environment that leverages this difference and thus destabilizing the system and affecting a separation. Typically in a milk system the first process chosen is one that increases the effect of gravity which results in separation based predominantly on density, and partially on fat globule size, through use of a disc centrifuge. Centrifugation results in two product streams: cream (a low density fat rich stream); and skim milk (a high density
Figure 1: Schematic of methods for promoting casein micelle aggregation: neutralizing surface charge by acid addition and removal of surface charge by enzyme (rennet) addition.
New Zealand Association of Science Educators
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