Storage of milk powders under adverse conditions

Abstract

1. Whole-milk powders containing 25 g water/kg were stored for up to 9 weeks in sealed aluminium containers at elevated temperatures. Lysine and other essential amino acids were measured by chemical and microbiological methods.2. Storage at 60' resulted in the progressive formation of lactulosyl-lysine. After 9 weeks, 30% of the lysine groups were present in this form. The powders still retained their natural colour and the levels of tryptophan, methionine, cyst(e)ine and leucine remained unchanged.3. Storage at 70° resulted in the formation of lactulosyl-lysine followed by its complete degradation with the development of browning. Available tryptophan, methione, leucine and isoleucine decreased progressively during storage.4. The different methods for lysine determination gave widely dissimilar results. The direct fluorodinitrobenzene (FDNB) technique and reactive lysine from furosine were considered to be the most reliable methods. The FDNB-difference, dye-binding lysine, Tetruhymena and Pediococcus methods all seriously underestimated reactive or available lysine in heat-damaged milk powders. Tetrahymenuand Pediococcus appeared to utilize lactulosyl-lysine as a source of lysine.5. The results are discussed in relation to storage and distribution of milk powders in hot climates.During prolonged storage of milk powders, Maillard reactions between milk proteins and lactose may reduce the level of lysine and other essential amino acids. The loss of lysine, the most sensitive amino acid to Maillard damage, increases with increase in temperature and moisture content (Erbersdobler, 1970) and hermetic packaging and cool storage conditions are necessary to reduce the reaction to a minimum. Lysine has been reported to be reasonably stable for at least 1 year in low-moisture milk powders stored in moisture-resistant containers at temperatures up to 37 ' (Henry et al. 1948;Rolls & Porter, 1973; Womack & Holsinger, 1979). In temperate climates, distribution and storage would therefore appear to present little possibility of large losses of amino acids. In hot countries, however, where distribution networks are often less developed, milk powders may be subjected to high temperatures (above 40') at some stage during their transport and storage. Little information is available on the losses of nutrients under these more extreme conditions. In the present paper, we report the losses oflysine and of other amino acids in low-moisture milk powder (25 g water/kg) during storage at high temperatures, and high-moisture powder (100 g water/kg) stored at 37' . At the same time, we have extended earlier studies (Finot & Mauron, 1972;Finot, 1973;Hurrell & Carpenter, 1974 on the ability of different lysine assay methods to accurately predict the extent of lysine damage after Maillard reactions. The dye-binding lysine and furosine techniques, and microbiological methods with Tetrahymena and Pediococcus, have been evaluated. Test materialsSpray-dried whole-milk powder containing 25 g water/kg was packed under air into aluminium cans (4...

Effect of storage conditions on furosine formation in milk–cereal based baby foods

“…Furosine content has been used to estimate the percentage of blocked lysine in samples similar to those used in this study, such as different types of milk subjected to varied thermal treatments (Bujard  Finot, 1978;Finot, Deutsch  Bujard, 1981;Evangelisti et al, 1999a) and during storage (Hurrell, Finot  Ford, 1983), and also in cereal and milk products (Erbersdobler  Hupe, 1991;Pizzoferrato et al, 1998;Evangelisti, Calcagno, Zunin  Nardi, 1999b). …”

Determination of Lactulose and Furosine Formation in Heated Milk as a Milk Quality Indicator

“…Other study (Hurrell et al, 1983) has also reported that the lactulose concentration of the UHT milk was considerably higher than in nonfat dry milks. However, most of the UHT milk samples showed furosine concentration much lower than those of nonfat dry milk; this is because the extent of the Maillard reaction depends not only on the time and temperature of storage but also on the moisture content and the composition of the product.…”

Fluorometric determination of chemically available lysine: Adaptation, validation and application to different milk products

“…Different chemical methods (guanidation, reduction with sodium borhydride, fluorodinitrobenzene direct method and indirect difference method, dye-binding lysine) have been compared [8,20,21], the conclusion being that the determination of furosine and the Carpenter method (1960) are the most appropriate for estimating reactive lysine in milk. However, direct application of the spectrophotometric Carpenter method (1960) to foods having high carbohydrate or reducing sugar contents is not possible, because interfering compounds can be formed with the subsequent overestimation of reactive lysine.…”

“…The intensity of the thermal treatment applied in the manufacturing process and the effects of storage can be evaluated through the losses of available lysine (a specific marker of MR) [2,3]. Lactulosyl-lysine (e-N-deoxy-lactulosil-lysine), formed in the Amadori rearrangement of lactosyl amine, is the first intermediate compound of MR in milk, and is used as an indicator of the first step of the MR. Furosine detected for the first time in an acid hydrolysate of powdered milk [4] and identified, synthesized and characterized by Finot et al [5][6][7], results from the acid hydrolysis of the Amadori compound and permits the determination of lactulosyl-lysine [8][9][10]. Furosine content yields an estimation of blocked and therefore non-reactive lysine [8,[10][11][12], and is considered the most specific indicator of the first MR steps.…”