20 MASS. EXPERIMENT STATION BULLETIN 437 



Containers 



Because of the humidity and temperature conditions in a home freezing cabin et 

 the selection of adequate containers and wrapping for home frozen foods is of 

 utmost importance. The air in a home freezer is dry because most of its moisture 

 is frozen out and deposited on the walls and freezing coils in the form of ice or 

 frost. The dry air can take up moisture from improperly packaged foods and 

 leave them with a dry and spotted surface called "freezer burn." The degree 

 of "freezer burn" and loss of quality increases with the length of storage time. 

 To prevent such a deterioration of frozen foods during storage, it is essential 

 that the package or wrapping be air-tight and moisture-vapor-proof. An ideal 

 container is moisture-proof and can be sealed so that no liquid, vapor, or air can 

 get into or out of the packaged product. 



An excessive accumulation of frost on the inside of the freezing cabinet may 

 be an indication that some or all of the food is improperly packaged and is losing 

 moisture. The accumulation of frost inside the cabinet is also caused by freezing 

 the moisture out of air that enters when the cabinet is opened. This condition 

 is accentuated when the cabinets are opened frequently in warm, humid weather. 



Water-proofness is not the same as moisture-vapor-proofness. Ordinary 

 waxed or oiled paper is water-proof, but not moisture-vapor-proof. 



A satisfactory package for home or locker frozen foods should have the follow- 

 ing characteristics and properties: 



1. Must be moisture- vapor-proof. 



2. Must be leak-proof. 



3. Must protect food from absorbing and giving off flavor and odor, and 

 should not impart a flavor or odor to the food. 



4. Should not absorb grease, oil, or water. 



5. Must be durable. 



A partial list of sources of supply for packages and sealing materials is pre- 

 sented in Appendix 2. In addition to the various types of fiber containers avail- 

 able for packaging home frozen foods, home canning jars and tin cans are also 

 very satisfactory. If home canning containers are used, it is particularly impor- 

 tant that an adequate headspace (10 percent of the capacity of the container) 

 be left to allow for expansion of the product when it freezes. For home freezing 

 there is one objection to round or odd-shaped packages: they occupy greater 

 space in relation to their capacity than do square or rectangular packages. 



For heat-sealing many of the different types of paper or fiber containers, an 

 ordinary electric curling iron or a household flatiron is quite satisfactory. 



In the course oi home freezing and other investigations in this laboratory during 

 the past five years, over 10,000 jars of fruits, fruit juices, vegetables, meats, fish, 

 and poultry have been frozen under typical home-freezing conditions. Home 

 canning type jars were used in most cases. Glass containers are satisfactory 

 for home freezing as they provide a moisture-vapor-proof container which can 

 be re-used many times. No trouble from undue breakage has been encountered. 

 The objection to glass jars is that inherent in all cylindrical containers — they 

 take up more space in the freezer than do square-sided containers. This dis- 

 advantage would probably be offset by the advantages in many cases. 



