

Malcolm. — Com position of some Xew Zealand Foodstuffs. 269 



and coiled like a watch-spring — occur fairly often; they are probably 

 quite harmless. 



III. Kumara, or Sweet Potato. 



The kumara, or Maori sweet potato, is cultivated to a considerable 

 extent in the North Island of New Zealand. It seems to be the same as 

 the sweet potato of America and the Pacific islands generally, but some 

 slight differences in the composition were found, and these deserve to be 

 put on record. No complete detailed analysis was made. 



Carbohydrate. — Starch, in the form of granules which present the 

 usual appearance of batata-starch, constitutes the most important of the 

 solids. On hydrolysis it yields a dextro-rotatory reducing-sugar. 



Dextrin. — Fresh kumaras were extracted first with absolute alcohol to 

 remove sugar and other substances, then with cold water after driving 

 off the traces of alcohol. On adding alcohol this yielded a flocculent 

 precipitate when the alcohol present amounted to 60 per cent. This 

 precipitate was separated out and dissolved in water. It gave reactions 

 corresponding to those of a dextrin — viz., no reduction till after hydro- 

 lysis — and with iodine a dull-violet colour. 



Cane Sugar (?). — An alcoholic extract of kumaras contains all the 

 reducing-sugar present. If a watery solution of these sugars be hydrolysed 

 the reducing-power is markedly increased. Thus in two separate samples 

 the increase in reducing-power on hydrolysis indicated that 63'6 per cent, 

 of the sugar was in this form. 



Monosaccharide (? ). — A fresh watery extract of kumaras always shows 

 reduction. If left lying in the laboratory for a few weeks the kumaras 

 tend to grow mouldy, probably due to the sugars present, and the amount 

 of sugar of both kinds shows a slight increase (O'll per cent, in seventeen 

 days in one case). In the process of drying minced kumaras to produce 

 a powder for analysis there seems to be an increase in the amount of 

 sugar formed. If the drying is done on a water bath where steam can 

 reach the material, it forms gum-like masses, due to dextrin-formation, 

 so that for analytical purposes drying is best done in an oven. 



Protein. — The amount of protein is comparatively small, being at 

 most not more than 3 per cent., as indicated by the total nitrogen. An 

 estimation of the nitrogen in the flocculent precipitate obtained on boiling 

 a cold-water extract of kumaras indicated less than 1 per cent, protein. 



Fat. — The ether-soluble substances form a very small percentage of 

 the solids (0"27 per cent.). They resemble resins or oleo-resins more than 

 true fats, and it seems to be to these that kumaras owe their flavour. 



Ash. — The ash contains calcium, iron, magnesium, and phosphoric 

 anhydride. 



The following table gives the main points examined : — 



Tat)le IV. — Composition of Kumara. 



Sample 1. Sample 2. Sample 3. American. 

 Water, per cent. ... ... 68"44 67"7 77"35 690 



Solids (by difference), per cent, 3P56 323 22"65 3T0 



Starch, per cent. 



Cane sugar, per cent — 



Monosaccharide, per cent, 



Protein, per cent. 



Fat, per cent. 



A.sh, per cent. 



1 24-84 ' 3 ' 7 ^ 



262 

 2-7 217 



171 2-84 T73 13 



0-27 ... . . 0-6 



1-05 ... ... 0-8 



