30 MASS. EXPERIMENT STATION BULLETIN 388 



Chemical Investigation of the Onion. (Emmett Bennett). One paper on the 

 effect of storage of the Ebenezer onion has been published in Volume 39 of the 

 Proceedings of the American Society for Horticultural Science. 



A preliminary examination of the soluble carbohydrates indicates that the 

 reducing sugars are probably glucose and fructose. This indication is substan- 

 tiated by the formation of osazones characteristic of these sugars and by the 

 products of oxidation produced by iodine. According to the latter test the non- 

 reducing sugars are composed of approximately one third aldose sugar and two 

 thirds ketose sugar. This general distribution is to some extent substantiated 

 by the polariscopic behavior of solutions of the mixed sugar fractions. Prior 

 to inversion the optical rotation is usually slightly negative. After hydrolysis 

 the optical activity is decidedly more negative. Such response is usually in- 

 dicative of an inulide fraction. Further identification of these carbohydrate 

 groups by means of definite derivatives has not been successful. Analytical meth- 

 ods for other compounds concerned with the several phases of the project have 

 also been evaluated. 



Chemical Changes in the Cooking Quality of Vegetables. (Monroe E. Free- 

 man and W. S. Ritchie.) A new technique for estimating the texture of cooked 

 potato tissue was reported in the annual report for 1940. This technique has been 

 developed into a quantitative method based on the observation that mealy tissue 

 becomes porous on drying while waxy or soggy tissue becomes non-porous. The 

 pore volume of dried slices of tissue can be measured quantitatively by weighing 

 the samples under toluene when the pores are filled with air and when filled with 

 toluene. From these data the weight percent of toluene filling the pores can be 

 calculated and used as an index of texture. The samples were thoroughly dried 

 (in vacuo over P2O5), weighed in air and then under toluene. The weight of 

 the sample under toluene with all the pores filled with toluene was calculated 

 from the predetermined density of the potato dry matter and the density of the 

 toluene. Toluene indices ranged from 0.15 to values as high as 6.30 percent and 

 were easily reproduced within experimental error of ±0.05 to ±0.10 percent. 



The method was carefully checked by determining the specific gravity of a 

 large number of tubers, baking them, estimating the mealiness by personal 

 judgment, and measuring the toluene index. In all cases there was very satis- 

 factory agreement among these methods for estimating texture. Specific gravity 

 and judging method for texture estimation are rapid but distinguish only four 

 or five grades of texture. Toluene index is a longer and more technical method 

 but it has the distinction of offering a quantitative measure of potato texture or 

 cooking quality and therefore offers a great advantage to research workers in 

 this field. 



A storage experiment on potatoes is now under way to demonstrate the appli- 

 cability of this research tool. Samples of tubers are being stored at 35° and 50° F., 

 and in commercial storage. Samples will be withdrawn at intervals and the tex- 

 ture measured by the three methods, as above. 



Physico-Chemical Properties of Starches. (Monroe E. Freeman.) Very 

 little accurate information is available regarding the chemical and physical 

 properties of the different starches that control the properties of manufactured 

 dextrins, because the industry is operated largely as an art or a craft. The in- 

 troduction of precise scientific control can undoubtedly be facilitated bj^ the 

 accumulation of data on (a) the chemical and physical properties of the starches, 

 (b) the conversion process itself, and (c) the chemical and physical properties 

 of the dextrins. 



Experimental apparatus has been designed, constructed, and tested that 

 intimately mixes a fine spray of acid with a dust cloud of starch. Moisture con- 



