DAIRYING APPARATUS.

New Zealand Herald, Volume LXVI, Issue 20365, 20 September 1929, Page 7

DAIRYING APPARATUS.

METAL EFFECTS ON MILK. j

.vt RESULTS OF WORLD RESEARCH.

HOPES FOR NEW NICKEL-STEEL.

One of the most interesting branches of research in the dairying industry centres upon the effects on milk and milk-pro-ducts of the metals used in dairy, machinery. A very comprehensive report on the latest world-knowledge of tho subject has been supplied to tho*** Dairy Research Management Committee by Dr. F. H. McDowall, of the Dairy Research Institute. Palmerston North. There are two aspects of the problem of finding a satisfactory metal for use in the manufacture of dairy machinery, he states. Milk should not have a deleterious effect on the metal, and the metals should have no effect on milk or its products. The metal should be non-corrosive, stainless, a good conductor of heat, and reasonably easily worked into the shapes required. A wealth of research had been centred upon the effect of metals on miik and its products. It had been shown that small amounts of copper could cause offi flavours in market milk. As small a proportion as one part in 1,000.000 in butter could cause " fishiness" and " tallowness." Rusty cans wero often responsible for a metallic flavour in but* ter, and in milk for marketing purposes.. It had recently been demonstrated, too, that oiliness in milk could result from tho use of a cooler of tinned copper from which the tinning had been partly, <:'■! worn away. - . ' Metallic Salts in' Produce. Tho effect of small quantities of metallic salts in dairy products had a special significance to New Zealand since the faults engendered by their presence were for the most part ovidcut only after storage for some time. While some metals were under test at the Dairy Research Institute, stated Dr. McDowall, his present report mainly embodied fhe result of observations and inquiries made during a recent world tour. Dealing first with copper, tho report stated that from tho points of view of ease of working, smoothness of surface, mechanical strength and. even, in mauy cases, durability, it was a very suitable metal for dairy equipment, and'in former years was quite widely used in the industry. It had been shown, however, I hat copper was dissolved in appreciable quantities even by fresh milk. Tests and difficulties in practice had led largely to the elimination in dairies . of bare. . copper surfaces in places where they came v# •'= in contact with* milk. This elimination, however, was by no means complete. The copper pipe was still being used in many countries for the transference of milk C/j from one holder to another, and - the copEer evaporating pan for condensing miik { \i". ad not been superseded in any country, although in the future nickel might prove a suitable substitute. Dangers ol Worn Tinning. In New Zealand dairy practice them was no opportunity for cheese milk to take up. appreciable amounts Of copper, but in 'many butter factories there were coolers auid holding tanks for cream from which fhe tinned coating had been worn. Such equipment was a source of great danger. Examples were cited of New Zealand butter which, due to a copper taint, had been rendered quite unfit for human consumption by tho time it arrived in England. In spite of their disadvantages, tinned copper, brass, iron, and steel had not been superseded in any country for general dairy work. The fact remained, however, thai tho tin coating on copper or steel was not entirely satisfactory. w When the sheet of iron or copper was smooth and the tin coating had been well applied, it acted as a good protective agent. However, tin was quite appreciably . T;f. soluble in fresh milk and in lactic acid. It was not immune from the action of strong alkaline solutions used for cleans- .V':'ing purposes and, as it was very 6offc, itwas easily removed by mechanical wear. Recent tests in somo butter, factories near Palmerston North had shown that there 'was a distinct rise in ' the ..copper content of cream held overnight'in vats showing only a small surface of bare copper. j / Aluminium and Alloys. From many points of viewl aluminium was a very suitable metal for dairy equipment. It was relatively inexpensive, easy to fabricate, and although distinctly soluble in milk, aluminium salts • were almost tasteless and had no effect on flavour and keeping qualities of milk and dairy products unless they had a very high acidity. Aluminium was not, however, regarded as a suitable metal for whey, storage tanks, and a general disadvantage was its softness and lack of strength. . . . Nickel was more readily soluble than tin in milk and milk-products, more especially in milk with a high acidity. Loading research workers, however, had shown that the metal had no appreciable effect on the flavour and quality of sweet milk. Hitherto the use of nickel in dairy equipment had been limited by expense and by difliculties of fabrication. Both difficulties were being overcome and the metal was being extensively used in America for dairy purposes. As a coating on other metals, nickel was not a satisfactory protective agent. A nickel cooler was under trial at the Massey Agricultural College dairy ■ factory. * A Steel with Possibilities. Copper-nickel alloys were, widely used for milk pipes and connections, for winch they were more suitable .than > for vats and little was seen of them in cheese and butter factories. • . Opinions as to the value of stainless steel in the manufacture of dairy equipment were at variance, but Dr. Mc- •: Dowall expressed the opinion that at least two grades widely tested could not be regarded as suitable substitutes for tinned copper in ordinary dairy prae- -..jg. tIC As a result of laboratory tests made by Professor Hunziker, at least one class of chromium-nickel steel was regarded as i the most suitable material for dairy pur- •*/. poses on account of its slxnost coroplct© f resistance to the corroding action of milk : and its products. It appeared thai where great durability was required, chromiumnickel steels would eventually replace •;/( glass-lined equipment for most purposes, and probably they would also replace tinned copper or ' enamelled steel for rpany types of dairy equipment. MATURITY OF CHEESE. In advices received from the director of the dairy division, Mr. W. M. Singleton, who is on a visit to Europe, he makes ' several recommendations for improving •the maturity of cheese made during August and September, and for safeguarding against soft crowns. » : ! Ho suggests that factories instal steam /•< heating pipes iB curing rooms to centred the curing temperatui'o at from... 65 to 69 degrees Fahrenheit. Tho curds should bo cooked and not m&jM manufacture. All cheeses shou d be so made that each will have not than,. half an inch of air-space on t if each compartment of the crate.