Milk secondary drying

Commercially available nonfat dried milk and dried buttermilk have also been shown to contain small but detectable levels of NDMA (, , ). It has been suggested that N-nitrosamine formation is possible in foods that are dried in a direct-fired dryer (65). In such a dryer, the products of combustion come into direct contact with the food being dried, and N-nitrosamine formation is probably due to the reaction between secondary and/or tertiary amines in the food and the oxides of nitrogen that are produced during fuel combusion (65). 

Lipid hydroperoxides are either formed in an autocatalytic process initiated by hydroxyl radicals or they are formed photochemically. Lipid hydroperoxides, known as the primary lipid oxidation products, are tasteless and odourless, but may be cleaved into the so-called secondary lipid oxidation products by heat or by metal ion catalysis. This transformation of hydroperoxides to secondary lipid oxidation products can thus be seen during chill storage of pork (Nielsen et al, 1997). The secondary lipid oxidation products, like hexanal from linoleic acid, are volatile and provide precooked meats, dried milk products and used frying oil with characteristic off-flavours (Shahidi and Pegg, 1994). They may further react with proteins forming fluorescent protein derivatives derived from initially formed Schiff bases (Tappel, 1956). 

N-Nitrosamines, formed principally from the reaction of naturally occurring secondary amines with nitrites that may be added to foods or produced by bacterial reduction of nitrates, have been identified in many food systems including cured meat products, nonfat dried milk, dried malt and beer. In addition, the presence of less volatile and non-volatile N-nitroso compounds or their precursors in foods have been suggested from a number of model system studies. 

Notes. When using biotin-labeled secondary antibodies instead of enzyme-labeled antibodies, you have first to detect biotin with enzyme-labeled (strept) avidin and proceed further with the Substrate Step (9). Do not add normal serum, non-fat dried milk, culture media or other potential sources of biotin to (strept)avidin-containing reagents. This may result in reduced sensitivity. Solutions containing sodium azide or other inhibitors of peroxidase activity should not be used in diluting the peroxidase substrate. 

The serum used in the blocking solution should be normal serum from the species in which the secondary antibody was raised. Store refrigerated (see Note 7). Alternatives include 3% BSA or 10% nonfat dry milk in PBS. 

An ELISA (enzyme-linked immunosorbent assay) allows for rapid screening and quantification of the presence of an antigen in a sample (Fig. 5-28b). Proteins in a sample are adsorbed to an inert surface, usually a 96-well polystyrene plate. The surface is washed with a solution of an inexpensive nonspecific protein (often casein from nonfat dry milk powder) to block proteins introduced in subsequent steps from also adsorbing to these surfaces. The surface is then treated with a solution containing the primary antibody—an antibody against the protein of interest. Unbound antibody is washed away and the surface is treated with a solution containing antibodies against the primary antibody. These secondary antibodies have been linked to an enzyme that catalyzes a reaction that forms a colored product. After unbound secondary antibody is washed away, the substrate of the antibody-linked enzyme is added. Product formation (monitored as color intensity) is proportional to the concentration of the protein of interest in the sample. 

Reagents. Anti-chicken egg albumin antibody (whole antiserum, produced in rabbit), HRP-conjugate polyclonal anti-rabbit IgG antibody (produced in goat), albumin from chicken egg white (ovalbumin), and bovine nonfat dried milk were purchased from Sigma-Aldrich Co (St. Louis, MO, USA). Primary and secondary antibodies were diluted 1 2000 and 1 4000 (v/v), respectively, in PBS/milk... 

Xanthan is used in the recovery of secondary and tertiary petroleum, as a carrier for agricultural chemicals, as a gelling agent for explosives, as a thickener for cosmetics, etc. Since it is not metabolized, it can be used as a calorie-free additive for puddings, salad dressings, dried milk, fruit drinks, etc. 

Secondary oxidation products, 456 Seed extraction, 187,188,250 Segregated oils, 246 Sei whale, 137,139 Selacholeic acid, 3 Selectivity, 209,449,451 Semi-drying oils, 244 Senedesmus obliquus, 517 Serine derivatives, 277 Sesame oil, 52, 87,88, 98,101-07 Sesamin, 87, 88 Sesamol, 88 Sesamum indicum, 87 Sesamum orientale, 87 Sex attractants, 142 Sharpies process, 241 Shea nut oil, 51,88,100,104-06 Sheep milk, 116,167-69 Sheep wax, 144... 

Amadori compounds with different amino acid residues have been detected in many heated and stored foods, e. g., in dried fruit and vegetables, milk products, cocoa beans or soy sauce. Amadori compounds are also found in the blood serum, especially of patients suffering from Diabetes mel-litus. As secondary amino acids, Amadori and Heyns compounds can be analytically detected by amino acid analysis (cf. protein section). 

Cellular proteins were transferred to nitrocellulose in a Trans-Blot cell (Biorad). The gel was pre-equilibrated in transfer buffer (0.7% acetic acid) for 30 min. The transfer was then performed with reversed polarity at 30 v overnight. The nitrocellulose was incubated in blocking buffer (5% Carnation non-fat dry milk in PBS) at 37 C for 30 min. The nitrocellulose was then washed in PBS-Tween (0.05% Tween-20 in PBS) three times for 10 min. A 25 mL solution of primary antibody (12.5 pL polyglue antiserum, 250 pL heat-inactivated horse serum, 24.7 mL PBS-Tween) was added for 1 h. After washing in PBS-Tween three times for 5 min, the secondary antibody solution (goat anti-rabbit IgG coupled to horseradish peroxidase, Cappel) was added for 0.5 h. The nitrocellulose was then washed in PBS-Tween three times for 5 min and PBS once to remove residual Tween. The blot was developed using diaminobenzidine as enzyme substrate. 

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