Jan. 15, 191S Changes in Sweet Potatoes During Storage 



337 



The data in Table I show that under the conditions of this experi- 

 ment the moisture content of the roots remains fairly constant. There 

 is a slight decrease in the moisture content, more marked in the 

 Southern Queen than in the Big Stem variety, during the curing process, 

 but on the whole there is comparatively little change in the percentage of 

 moisture. The loss of moisture is probably compensated in part by the 

 water formed by respiration, while the loss of substance by respiration 

 would increase the relative moisture content, thus tending to conceal 

 actual water lost. 



The percentage of starch shows a rather sudden decrease immediately 

 after the potatoes are dug. The subsequent decrease is more gradual, and 

 continues until a minimum is reached in March. After that time there is 

 a continuous rise in the percentage of starch until the last date on which 

 the potatoes were examined. 



Concomitant with the changes in the percentage of starch there is an 

 inverse change in the percentage of sugar. Corresponding with the first 

 sudden decrease of starch, there is an equally sudden increase in sugar. 

 Later the increase in sugar content is more gradual, and reaches a maxi- 

 mum at the time of the starch minimum. After the sugar content has 

 reached a maximum there is a gradual decrease, which, however, is not 

 as marked as the increase during the first part of the season. 

 ■ The course of the changes in the percentage of cane sugar follows that 

 of the total sugar in both varieties, but in the Southern Queen the invert 

 sugar after the initial rise shows an almost continuous decrease, whereas 

 in the Big Stem the invert sugar content also shows a distinct maximum. 



The total carbohydrate content in both types remains fairly constant; 

 consequently the numbers showing the loss (or gain) of starch between 

 the successive dates of sampling show a fairly close agreement with those 

 showing the corresponding' gain (or loss) of total sugar. The aberrations 

 are probably to be attributed partly to the loss of substance through 

 respiration, but mostly to nonconformity of samples. 



The data showing the carbohydrate transformation in sweet potatoes 

 stored at low temperatures (approximately 4° C.) are given in Table II. 



Table II. — Carbohydrate transformations in sweet potatoes in cold storage 



BIG STEM, FIRST LOT" 



Starch. 



Cane 

 sugar. 



Reduc- 

 ing 

 sugar 

 as glu- 

 cose. 



Total 

 sugar 

 as glu- 

 cose. 



Total 

 carbo- 

 hy- 

 drates 

 as glu- 

 cose. 



Gain or 

 loss of 

 starch 

 (as glu- 

 cose).'' 



Gain or 

 loss of 

 sugar 

 (as glu- 

 cose).'' 



Average 

 weekly tem- 

 perature. 



Mov. J. 



Dec. Q. . 

 Dec. a I . 



P.cl. 



72. V9 



P.cl. 

 16.94 



P.cl. 

 J- SI 



6.46 



P. cl. 

 ■•3> 



1.60 



P.cl. 

 5. 03 



P.cl. 



23. fia 



Gvi. 



-4. 03 



-2. 79 



+ 3-»o 



Week 

 ending — 

 Oct. 33 

 Oct. 30 

 Nov. 6 

 Nov. 13 

 Nov. 20 

 Nov. 27 

 Dec. 4 

 Dec. 1 1 

 Dec. 18 

 Dec. 35 



o The figures are alt calculated for the original water content of the roots, 73.50 per cent. 

 ^ Per 100 gm. of material. 



