26 MASS. EXPERIMENT STATION BULLETIN 287 



tmd point was reached. Thi.s method of titrating ices or sherbets for acidity is 

 therefore reconiinended because the equipment is always available in an ice 

 cream plant. 



SUMMARY 



Investigations on methods of freezing and utilization of frozen New England 

 fruits were carried on during three crop seasons. All the fruits studied were grown 

 in the college orchards, frozen, defrosted, examined, and later utilized in frozen 

 dairy products. In all, over 650 one-gallon cans of these fruits were frozen. 



1. Fruit varieties vary greatly in their suitability for freezing and for use in 

 ice cream. Of the 20 varieties of strawberries, the most desirable frozen 

 packs were Howard Supreme, King Edward, Marshall, Howard 17, 

 First Quality, Aberdeen, Boquet, Beacon and Bliss. The red-fleshed 

 varieties of strawberries gave higher colored frozen packs. The most 

 satisfactory raspberry varieties were Cuthbert, Herbert and St. Regis; 

 peaches, Hiley, Elberta, Hale and Crawford; cherries, Montmorency. 

 In general, yellow-fleshed varieties of peaches were more attractive than 

 white when frozen. 



2. While plums, red currants, nectarines, cranberries, blackberries, blue- 

 berries, black and purple raspberries, and rhubarb were successfully 

 preserved by freezing, these fruits cannot be considered entirely satisfac- 

 tory. Though not suited for use in ice cream, fairly satisfactory ices can 

 be made from them. Cranberry ice is particularly good. 



3. For one-gallon cans of fruit a freezing temperature of to -10° F. with 

 subsequent storage at 10 to 15° F. proved entirely satisfactory. A mod- 

 erately constant storage temperature is essential for maintaining the 

 quality of the pack. Defrosting and refreezing are definitely injurious 

 to both appearance and flavor of frozen fruits. 



4. The soluble solids content of 20 varieties of strawberries varied from 

 5.9 to 7.6; acidity (citric) from 0.9 to 1.43 per cent; ratio of fruit to 

 syrup in the 2:1 frozen pack from 1 :0.62 to 1:1.46: and Brix readings from 

 33 to 44 per cent. 



5. The sugar concentration (Brix reading) of the syrup of defrosted fruits 

 serves as an index of the original fruit to sugar ratio. (See Table 2). 



6. Discoloration in frozen fruits is normally limited to the surface layer 

 Although this injures somewhat the appearance of the fruit, little injury 

 to flavor results. Peaches were particularly subject to surface discolora- 

 tion. Syrup pa(!king reduced this defect considerably; vacuum sealing 

 practically eliminated it. 



7. In every case the addition of sugar to fruit before freezing greatly im- 

 proved the flavor, color and general appearance of the pack. Fruit to 

 sugar ratios of 2:1, 2.5:1, and 3:1 were most satisfactory for frozen 

 strawberries and raspberries. When the ice cream mix contained 15 per 

 cent sugar or less, the 2:1 or 2.5:1 packs should be used; while the 3:1 

 ratio was preferred when the sugar in the mix exceeded 15 per cent. 

 Cherries should be frozen with sugar in the ratio of 2:1, and peaches 

 with a 3:1 ratio. 



