Points (l) and (2) above occur as a result of imperfect stagger- 

 ing of the loins of tuna as th^ enter the filling machine. This stag- 

 gering is carried out by hand and requires considerable skill. Greater 

 uniformity in this operation can be attained both by using more skill- 

 ful operators and by increasing the number of workers feeding a machine. 

 Most plants use only one such feeder, but where two or even three such 

 workers are utilized, the resulting fill is much improved. When veiy 

 small fish such as skipjack are being canned, differences due to skill 

 of feeding the machine are especially critical. Even by using the most 

 skilled workers and employing several of than for each Pak-Shaper, it 

 is difficult to avoid some imperfect overlapping, with resulting voids 

 between pieces in many of the cans, 



A second type of change is brought about during kneeding of the 

 tuna loins within the forming tunnel of the Pak-Shaper, During this 

 operation, the loins are subjected to a twisting stress which distorts 

 the fibers. This results in some separation of the flakes. 



Another effect which may result from the machine packing of tuna 

 arises from greater absorption of oil by the fish. The distortion of 

 the muscle fibers in the Pak-Shaper results in the flesh having an in- 

 creased capacity to absorb oil. In such cases, unless a large quantity 

 of vegetable oil is added, the possibility exists that the surface 

 of the fish may not be covered by oil during retorting. This may con- 

 tribute to surface discoloration or so-called scorching. 



Apparently, there is a considerable variation in the amount of 

 distortion of the tuna fibers in the Pak-Shaper such as to make for 

 somewhat variable amounts of absorption of oil. Thus, if the same 

 minimum amount of oil is added to all cans, some '^dll have insufficient 

 free oil to cover the surface of the fish, A few packers overcome 

 this difficulty by adding an excess of oil. This practice, however, 

 may result in leaving inadequate headspace in some of the cans^ 



Comparison of the Quality of Oil and Brine Packs 



The principal difference between the oil and brine pack is the oil 

 content of the drained tuna. Use of brine in place of oil as a packing 

 medium results in a product containing no oil other than the natural 

 tuna oil left in the flesh after precooking. The precooking process 

 renoves a part of this natural oil. Since the oil content of tuna 

 varies widely both from species to species, and from fish to fish, the 

 amount of oil left in the flesh after pi^cooking also varies widely. 



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