15G STATE POMOLOGICAL SOCIETY. 



Citric Acid : Found in lemons, oranofcs, tomatoes, currants, o;oo'seberries, raspberries, 

 strawberries, and a larijo number of otber fruits, generally with malic and tartaric 

 acids. Obtained from lemons for use. 



Tartaric Acid: Also widely distril)Uted. in most friiits not form! nj^ the cliiefacid, 

 but constituting the acid of the grape. Manufactured from the deposit of ferment- 

 ing grape juice; used in baking powders and in its salts, cream-of-tartar, and 

 Rochelle's salt. 



0.\alic acid is sometimes found in small proportions in a few fruits. Rc])orts 

 vary as to its existence in the tomato. 



Frcsenius' analyses give the following as the average'proportious of total acid, 

 reduced to ecjuivalent of malic acid. 



Currant.. - 2.04 per cent. 



Easpberrv - - 1.48 " 



StrawbeiTV... - ....1.31 '' 



Sour cherry. - 1.28 " 



Apple . . .\. - 0. 75 



Grape - 0. 74 



Peach 0. G 



Red Pear.. ..0.07 '' 



a ,1 



74 " 



a 



The fpiantity of acids in fruits usually diminishes during ripening. The 

 diminution is not, however, nearly so great as it appears to tlie taste, because 

 the acid of ri[)e fruits is masked to the taste by the larger proportions of sugar 

 iind tlic pectous substances then present. The removal of acids is chiefly due 

 to oxidation. It is not found that acids are neutralized, to any considerable 

 extent, during ripening, by alivalies conveyed through tlie stem. Tlic diminu- 

 tion of the acid in j^lums was shown definitely by tlie series of analyses before 

 given from Mercadante. It is stated that the acids continue to oxidize away, 

 after the sugar has reached its maximum and before it begins to diminish. 

 Hence, jierfect rijieness in fruit has been defined as that period during the max- 

 imum quantity of sugar when tlie quantity of acid is least. This will be, of 

 course, just before the sugar begins to diminish. 



It has been stated that both citric and malic acids are often found in unriiDB 

 grapes, and are substituted by tartaric acid during the ripening. Oxalic acid is 

 more often found in unripe than in ripe fruits. It is to be desired that closer 

 determinations siiould be made as to the presence and proportion of oxalic acid 

 in tomatoes and some other fruits. Any article of food containing oxalic acid 

 (as the garden pie-plant) should probably be eaten with moderation, if at all. 



A misapprehension sometimes occurs, from lack of reflection, as to the effect 

 of sugar on the acidity of fruits. Sugar has no chemical effect upon acids. 

 Its very sweet taste masks or overpowers to the sense the sour taste of free 

 acids, — but the acids remain free, all the same. AV'hatever effect the sugar 

 eaten with fruits has on dio-estion and nutrition is due to the sugar itself ; not 

 to any change of the acids by the sugar, fur there is no such change. Indeed, 

 sugar approaches to the nature of an acid, though properly classed as a neutral 

 body. 



The varieties of tannic acids classed together as tannix are quite unlike the 

 fruit acids above mentioned, Ijoth in sensible properties and in chemical rela- 

 tions. Only a few of the ripe edible fruits contain astringent acids, though 

 these are found in many unripe fruits and in uumerou;^ ripe fruits not used for 

 food. Most varieties of colored grapes contain a little tannin deposited mostly 

 in the skins and seeds, and imparting a slight astringency to the juice, retained 



