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Hydrographic measurements from the 1994 Arctic Ocean Section show how the Makarov and Canada basins of the Arctic Ocean are related, and demonstrate their oceanographic connections to the Eurasian Basin. The inflow into the Makarov Basin consists largely of well-ventilated water within a broad band of densities from a boundary flow over the Siberian end of the Lomonosov Ridge. The boundary flow contains a significant component of dense shelf water likely originating in the Barents, Kara, and Laptev Seas. Earlier ice camp data show that the Canada Basin is relatively more isolated from this ventilation source. In the Canada Basin shelf sources influenced by Bering Sea water appear to add cold waters with high silicate concentrations to the halocline and deeper. In 1994 the halocline silicate maximum over the central Makarov Basin was absent, evidence of the recent displacement of the upper (S∼ 33.1) halocline water from the Chukchi-East Siberian Sea region by water from the Eurasian Basin. Much of the Makarov Basin water in and below the halocline is in fact from the Eurasian Basin, with admixture of waters from the Canada Basin suggested by their higher silicate concentrations. Mid-depth eddies may transport anomalous properties into the central Arctic and create property gradients or fronts in mid-depth and deep waters. The complex topography of the Mendeleyev Ridge-Chukchi Plateau region also may assist spreading of water from the boundary into the interior. Atlantic layer characteristics in 1994 differed from previous general depictions. In particular the core temperatures at the Chukchi-Mendeleyev boundary were at least 0.2°C warmer on average than indicated in earlier work. The recent warming at intermediate depth has resulted from inflow of Atlantic waters that have been cooled relatively little during their transit of the Norwegian Sea.

Potential temperature (θ) and salinity (S) data obtained along the perimeter of the southern Canadian Basin north of the East Siberian Sea in 1993 aboard the CCGS Henry Larsen show higher temperatures in waters of Atlantic origin than in available climatological data for the Canadian Basin. In particular, a front is observed near the Mendeleyev Ridge which separates the cooler Atlantic waters of the Canada Basin from the warmer Atlantic waters observed in the Makarov Basin. The front is further characterized by a change in the θ/S slope of Arctic thermocline water, and by thermohaline intrusions (θ and S reversals) within the Atlantic layer. The idea that this warm variety of Atlantic water has come recently from the Eurasian Basin is supported by its higher level of the tracer CFC-11.

The freezing point of seawater has been measured in the salinity range 18‰ < S ≤ 35‰ at atmospheric pressure showing results consistently lower than Hansen's (1904) values. Our data fit the curve Tƒ = −0.036 - 0.0499S -; 0.000112S2 with a standard deviation of ±0.0025°C. This equation also stays within −0.01°C of Hansen's data in the range 9–35‰. Determinations of the change of freezing point with pressure were made for three salinities in the range 27‰ < S ≤ 35‰ showing a constant slope of 7.59×10−3 °C/bar up to 100 bars independent of salinity.

The flavour and nutritional quality of UHT processed milk is discussed and suggestions are made for ways of minimizing undesirable changes during heat treatment. UHT treatment of milk using an infusion heater is described, and it is concluded that whole milk processed in this way is a typical directly heated UHT milk.

SummaryIndirectly heated ultra-high-temperature (UHT) processed milk was prepared with initially high, medium, and low dissolved O2 contents of 8·9, 3·6 and 1·0 ppm respectively, aseptically bottled, and tested at intervals during storage at room temperature for 150 d. Flavour acceptability increased to a maximum after a few days, but declined slowly after about 6 d; the increase was associated with less off-flavour described as ‘cabbagey’, and the decrease with more ‘stale’ off-flavour descriptions. Milks with higher initial O2 contents were preferred up to 8–13 d, but thereafter acceptability was independent of initial O2 content. Sulphydryl group (–SH) contents rapidly decreased and O2 levels correspondingly declined in the first few days as the flavour improved. Loss of –SH was lower with lower initial O2 contents, and moderate –SH content remained in low O2 samples for several weeks. Ferricyanide reducing (FR) values did not satisfactorily measure stale flavour development. They were initially high and decreased during the first 13 d at rates dependent on O2 content. After 20 d the FR values began to rise in high O2 samples, but continued to decline slowly in low O2 samples up to 90d although stale flavour was increasing.High initial O2 contents resulted in rapid depletion of ascorbic acid and folic acid during storage. Losses of vitamin B12 were small, but were higher with high O2 contents than with low.The beneficial effect of O2 on flavour, therefore, appears to be so slight and confined to such a short period in the early life of the milk as to be completely outweighed by the adverse nutritional effects.

SummaryAn experimental ultra-high-temperature milk sterilizer, of 1140 1/h capacity and capable of operation as a plate-type indirect heating plant or as a steaminto-milk direct heating plant, has been installed for comparisons of the milk produced by the direct and indirect processes. The sterilizer and its ancillary equipment are described, together with methods of plant sterilization and milk processing. Time-temperature profiles of the plant are given for both modes of operation.

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SummaryThe distribution of protein nitrogen was determined in milk treated by an experimental ultra-high-temperature (UHT) plant, operating alternatively as an indirect or as a direct heating plant.The extent of denaturation of β-lactoglobulin can be used to assess the relative severity of UHT heat treatments; this criterion was used to compare the indirect and direct arrangements of the plant with each other and with other published results.The time-temperature profiles of the plant were used to calculate the expected extent of denaturation of β-lactoglobulin during treatment of the milk. The results of the calculations are in fair agreement with the analytical results.

SummaryThe variation of sporicidal efficiency with processing temperature was determined for an experimental ultra-high-temperature (UHT) milk sterilizer operating alternatively as an indirect or as a direct heater. Whole milk was inoculated with large numbers of spores of Bacillus subtilis 786 and Bacillus stearothermophilus TH24, and the proportion of spores surviving the sterilizing process was calculated from dilution and colony counts on the untreated and treated milk. The results for B. subtilis spores were unreliable, and the dilution count results for B. stearothermophilus spores were influenced by the inhibitory effect of the UHT processed milk. The results for the colony counts of B. stearothermophilus spores were preferred as a basis for the comparison of the direct and indirect processes. Over the range of processing temperatures 137–145 °C it was found that the sterilizing temperature had to be 3–4 degC higher with direct heating than with indirect heating to give equal spore destructions.

SummaryWhen heat treatments of the same sporicidal effectiveness were given, directly heated ultra-high-temperature sterilized milk gave twice as much sediment as indirectly heated milk after storage at room temperature for 100 days. Both types of process reduced the rate of clotting of the milk with pepsin and rennin, but the effect of the indirect process was markedly greater than that of the direct process.

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SummaryA comparison was made of the effects of direct and of indirect ultra-high-temperature (UHT) processing of milk, under standardized operating conditions giving equal sporicidal effects, on some of the more labile water-soluble vitamins and on vitamin A and carotene. The effects of processing per se were negligibly small, and the method of processing was important only in so far as the presence of residual oxygen in the sterilized milk has been found to cause losses of folic acid and ascorbic acid during storage subsequent to sterilization. The incorporation of a de-aerator vessel, to reduce the oxygen level in the indirectly heated milk and so eliminate the adverse effects of oxygen during storage, had no effect on the vitamin loss occurring during heat treatment. It is concluded that milk produced by indirect heating plant incorporating a de-aerator should be similar in vitamin content to milk produced on a direct heating plant, both immediately after processing and after storage.

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A method for determining low concentrations of hydrogen peroxide (H2O2) in water, based on the chemiluminescent oxidation of 3-aminophthalhydrazide (luminol) by H2O2 in the presence of a copper ion catalyst, is described. Levels of H2O2 down to 3 × 10-8 mol/1 (1 ppb) can be determined. The method may be used to monitor the amount of residual H2O2 in aseptically filled packages sterilized with H2O2 before filling.