Medium packed
Solid pack 29.9 9.0 58.2 2.9
Medium packed
Chunk style 28.0 9.3 60.0 2.7
Medium packed
Grated style 27.2 13.3 57.0 2.5
T h e nutritive value of fish is high ( M c L e s t e r , 1 9 4 4 ) . As a good protein food it is h i g h in essential a m i n o acids. T h a t t h e high nutritive value o f t u n a is not affected adversely b y the canning process has b e e n demon
strated b y t h e work o f Neilands et al. ( 1 9 4 7 ) a n d D u n n et al. ( 1 9 4 9 ) . C a n n e d tuna, in c o m m o n with other fish foods, is low in connective tissues and is highly digestible. C a n n e d tuna contains important t r a c e minerals high in iodine and fluorine. I t is a good source of several of the water-soluble vitamins of t h e B - c o m p l e x , such as nicotinic acid, pyri-doxine, riboflavin, pantothenic acid, and biotin. I t is also a fairly good source of vitamin D . An analysis of t h e a v e r a g e composition of some of t h e various styles o f c a n n e d t u n a is given in T a b l e V .
W i t h i n r e c e n t years, various c a n n e d specialty products m a d e from tuna have b e e n appearing on t h e m a r k e t ( d i e t e t i c tuna, t u n a and noodles, e t c . ) . W h i l e t h e consumer response to these products at the m o m e n t seems to b e limited, it is p r o b a b l y too early to p r e d i c t t h e future potentialities of these products.
T h e final j u d g m e n t on t h e suitability o f t h e pressed w e i g h t as a practical and a c c u r a t e index of fill of c a n will h a v e to b e delayed until the tuna canning industry and t h e F o o d and D r u g Administration have used it long enough to fully appreciate its merits.
T h e c a n size designation used in the a b o v e and in industry generally is derived from its nominal dimensions. T h e first digit represents whole inches, t h e next two t h e extra fraction expressed as sixteenths of an inch.
T h e diameter is cited first, followed b y the height ( C a n n e d F o o d R e f e r e n c e M a n u a l , 1 9 3 9 ) .
T h e T u n a Standards also regulate the labeling permitted for the various styles o f p a c k o f c a n n e d tuna. I n a s m u c h as labeling, as such, does not involve any points of technological interest, this aspect of the T u n a Standards will not b e further discussed.
2 4 2 SVEN L A S S E N
X. Quality Control of Canned Tuna
Quality control is necessary to produce a uniform and a c c e p t a b l e c a n n e d tuna product. T h e quality control used in the tuna canning industry has for m a n y years consisted of "cutting" a certain n u m b e r of cans from e a c h lot produced, and examining the content b y an orga
noleptic appraisal, and b y measurements of drained weights, c a n vacuum, etc. T h e yearly industry-wide tuna cutting, w h i c h was initiated some years ago b y the California tuna canners, e n a b l e d m e m b e r s of the industry to compare, and score, t h e quality of their own product with c o d e d samples of those of their competitors. T h i s gave the c o n c e p t of quality a n d quality control a strong stimulus. T h e r e c e n t introduction of the T u n a Standards has further helped to give quality control the important p l a c e in the over-all tuna canning operations w h i c h it right
fully deserves. T h e result has b e e n that quality and uniformity of product are now b e i n g measured on a rational basis. T h e variation in composition of the tuna r a w material, due to variation in size of tuna, texture, color, salt content, state of dehydration, etc., makes it a major p r o b l e m to obtain uniformity in c a n n e d pack. I t has, therefore, b e c o m e necessary to employ chemical, physical, and statistical methods of analysis of the c a n n e d product in order to exert proper quality control, and to regulate the flow of t h e tuna m e a t through the canning e q u i p m e n t so that the content of tuna in any c a n complies with federal requirements.
T h e cans necessary for the canning of tuna are usually supplied ready-made, with lids, b y the major can companies, in sizes w h i c h h a v e b e c o m e standard for the tuna industry. T h e cans are now c o a t e d on the inside with a special e n a m e l to preserve the natural characteristics of the tuna meat. T h e introduction of the enamel-coated can, some ten years ago, has practically eliminated the occasional discoloration of tuna in some cans due to iron sulfide w h i c h resulted from c o n t a c t b e t w e e n the steel b a s e of the sometimes inadequately tin-coated c a n a n d the sulfur-containing amino acids of the tuna protein.
W h i l e the sanitary tin can, with or without e n a m e l coating, has shown a remarkably w i d e range of application for all types of c a n n e d food products, t h e successful use in other countries of aluminum cans for fishery and other foods, and the r e c e n t lowering o f the price of aluminum, m a y in the future see the aluminum c a n enter into competition with the tin c a n in the field of tuna canning and other c a n n e d products. A strict quality control of the material from w h i c h the cans are m a d e as well as of t h e cans themselves is maintained b y the c a n companies, and is, therefore, usually not included in t h e duties assigned to cannery quality control ( s e e Am. Can Co. Bull. No.
4800).
4. T U N A CANNING AND P R E S E R V A T I O N O F R A W M A T E R I A L 2 4 3
XI. Concluding Remarks
I n presenting a general description and discussion of the principles of tuna canning, and the preservation of the tuna raw material while in transit from the fishing areas to the shoreside cannery, the author has naturally b e e n guided b y his long experience with t h e methods and technology as used b y the tuna processors on the Pacific C o a s t of the U n i t e d States. T o describe and discuss these methods in preference to possible modifications thereof practiced elsewhere, is justified b y the fact that the Pacific Coast tuna processors produce b y far the major part of the c a n n e d tuna consumed, not in the U n i t e d States alone, b u t in t h e whole world. T h u s , although it is known that minor deviations from this m e t h o d of tuna processing are p r a c t i c e d in other countries and, to some extent, within the U. S. tuna industry, these deviations are, at t h e moment, not considered to b e of sufficient importance to b e discussed in the limited space available here, nor do they alter in any essential w a y the general features of t h e t u n a canning process w h i c h has b e e n outlined and presented in this chapter.
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