Oils and Fats. 



370 



(7) Most of the free acid and the accompanying bad odour and taste is 

 produced in the copra itself before the oil has been expressed. The oil from a 

 sample of copra which had been cut into fine pieces and exposed to moist air 

 for one month increased in acidity from 1*5 to 23-3 per cent. 



(8) The hydrolysis and subsequent destruction of fat in copra is brought 

 about by moulds (the greater part of which are Aspergilli) acting either alone or 

 in symbiosis with certain bacteria, the condition most favorable to this growth 

 being a moderately high, constant temperature and a water content of from about 

 9 to 17 per cent. No organisms were found growing on a sample containing 4'76 per 

 cent of moisture and no change in acidity took place. Samples containing from 

 23 to 50 per cent of water were infested by several species of bacteria which sub- 

 sisted in the nonfatty portion of the copra, but produced very little free acid from 

 the oil. No moulds were found in these samples. 



(7) Ordinarily, commercial copra contains from 9 to 12 per cent of moisture, 

 a very favourable condition for mould growth. The remedy for this rapid deterior 

 ation is simply to dry it so that it contains not more than 5 per cent of moisture, 

 and express the oil as soon as possible, avoiding - long storage in a warm, moist 

 atmosphere. 



Drying. — By comparing the various methods of copra drying, a hot air 

 apparatus, either rotary or stationary, was found to be the most efficient. It is 

 suggested that a combination of centrifugal with hot air drying might prove of 

 considerable value, provided a market could be obtainable for the by-product 

 " coconut cream." Vacuum drying is not of great value in the desiccation of 

 coconuts for oil-making purposes. 



(10) Although a pure coconut oil is not a suitable medium for a growth of 

 micro-organisms, one containing a sufficient amount of nutrient matter and moisture 

 may, under certain conditions, develop a growth of mould which rapidly attacks the 

 oil itself. A sample of pure oil to which had been added 1 per cent of " latic " and 

 1 per cent of water increased in acidity from 0*10 per cent to 8*63 per cent on 

 standing exposed to mould action in an incubator for one week. 



The very slight increase in acidity which a pure oil suffers on long standing 

 is probably due to simple hydrolysis by heat and moisture. 



(11) Besides the production of free acid by moulds and the decomposition of 

 albumen by bacteria in moist copra and in impure oils, one other factor enters into 

 the deterioration of coconut oil. Many samples on long standing develop a slight 

 but noticeably acrid taste and odour, without any marked increase in acidity. Such 

 oils invariably give a blue colouration with Schiff's aldehyde reagent, reduce silver 

 nitrate in Becchi's test for cotton-seed oil and possess the power of liberating iodine 

 from potassium iodide. This process is shown to be a direct oxidation by the air 

 and to depend largely upon the amount of surface exposed. Other conditions 

 favouring it are freedom from moisture and impurities, as is shown by the fact 

 that impure commercial oils, or those which have been acted upon by mould, do not, 

 as a rule, respond to tests for peroxide and aldehyde, while the most marked 

 development of these bodies is noticed in the purest oils. 



(12) The action of light and air on coconut oil is of relatively little 

 importance in comparison with the great changes produced by mould growth, and 

 it can be prevented in a large degree by keeping oil receptacles as nearly full as 

 possible, so as to reduce the amount of surface exposed.— Philippine Journal of 

 Science, Vol. 1, No. 2. 



[This is the summary of a long scientific paper on this subject. The 

 Americans are already setting to work at the scientific investigation of agriculture, 

 and similar matters in their new possessions, and already the scientific staff at 

 Manila is more than twice as large as that at Peradeniya.— Ed.] 



