Testing Milkofix, a new preservative preparation for milk samples used for infrared analysis of milk components. II. Verification of its preservative effects in relation to infrared analysis]

For the purposes of the infrared analysis of the basic milk composition, Milkofix, an ecologically friendly preparation used for milk sample preservation (Trzicky, 1990), was compared with untreated samples (N) and with samples preserved with sodium azide (A), bronopol (B) and potassium dichromate (C) at a storage temperature of 20 degrees C (I) and 4 degrees C (II) in samples kept for 14 and 18 days. Pursuant to the recommendations cited in literature, the preservatives had these concentrations: A = 0.0085 g NaN3 and 0.0630 g NaCl; B = 0.0050 g bronopol and 0.0500 g NaCl; C = 0.0330 g K2Cr2O7 and 0.0670 g KCl; M = 0.1250 g, all amounts are per 25 ml milk. Three bulk milk samples were used which were analyzed on an automatic Milko-Scan 133 B infraanalyzer (Foss Electric, Denmark) every day. On the basis of a graphical evaluation of the results by IDF recommendations (1985) the times within which the applicable results could be obtained were determined for the various methods of milk sample treatment (Figs. 1 to 6): N I--0 days; A I--9; B I--10; C I--13; M I--4; N II--10; A II--5; B II--11; C II--15; M II--10 (Tab. I). The results recorded for Milkofix are in agreement with the conclusions drawn in the previous study, where the intervals of four and nine days were determined. The days to milk sample coagulation were as follows: N I--1 day, M I--10 days. The coagulation in A I, B I, C I and N II samples was not observed even after 13-day storage and in A II, B II, C II and M II samples not even after 17 days of storage. The results for particular components (fat, proteins, lactose) of milk samples differently treated in time are presented in Tabs. II, III and IV. A system of evaluating criteria (Tab. V) was used to determine the order beginning from the most convenient method of milk sample treatment for the given purpose: 1. C II, 2. C I, 3. B II and A I, 4. B I, 5. M II, 6. N II, 7. A II, 8. M I and 9. N I.(ABSTRACT TRUNCATED AT 400 WORDS)