234. 



TECHNICAL BULLETIN 15 



malic acid constantlj- present in the fruit. No ;icid was added after the first 

 extraction had been made. 



Table 12 and Chart 5 show the effect upon soluble solids and pectin yield 

 of extracting in the presence of increased acidity. In general a slight but 

 uniform increase in the amounts of soluble solids, including jjectin and malic 

 acid, was obtained wtih increased acidity. This increase was more marked 

 in the case of sliced than of chopped fruit. An acidity of 0.4 per cent tar- 

 taric acid was practically as efficient as double that amount. In other words 

 beyond a certain point little or no advantage accrued from increasing the 



Chart 5. Effect of Added Acidity upon the Kecovery of Soluble Solids and Pectin in 

 First and Second Extracts of Sliced and Chopped Apples. Ratio of Apple 

 to Water 3:3. 



a 50 



140 - 

 I 50 



20 



10 







FIRST EXTBACTIOK 

 SE.C0HO E,XTHACT10K 



Sliced Chopped 



SOLUBLE SOLIDS 



Sliced 



Chopped 

 PECTIN 



*Per cent added aciidity. 

 acidity. There was but little effect upon the second or third extracts; the 

 increased yields of solids and pectin being much more pronounced in the first 

 extract. In l)ut few cases did the addition of tartaric acid in order to in- 

 crease the natural acidity of the fruit, produce more than a 10 per cent in- 

 crease in yield of solids or pectin even in the first extract. Pectin extraction 

 was aided somewhat more by the acid than was the extraction of soluble 

 solids; in neither case was the increase appreciable, especially if two extrac- 

 tions were considered. 



It is questionable whether the addition of organic acids to apples yielded 

 a sufficiently richer juice to pay for the trouble. The resulting jelly was 

 improved in quality, yield, color, and taste by the acid, though of course if 

 sold, a declaration of added acid would be required by State and Federal 

 food laws. However, addition of acid may be advantageous on other grounds 

 inasmuch as Tarr (17) has demonstrated that the hydrogen ion concentration 

 must be at least 3.46 for jelly formation using pure pectin, with the optimum 

 from 2.9 to 3.0. It is likewise true that added acid in many cases appreci- 

 ably increased jelly yields and improved its physical properties and flavor. 

 For some non-acid varieties of apple a distinct improvement in jelly flavor 

 was effected 1)V the addition of a small amount of acid. 



