The proportionate percentage of body components of whole 

 krill according to Grantham (1977) are about 28% tail meat, about 

 34% cephalothorax, and about 26% carapace. The remaining 

 12% is exudate lost on separation of the body parts. 



Protein. — According to Grantham (1977), the 13% wet weight 

 of protein appearing in Table 1 comprises about 8.5% true protein 

 and 2.5% free amino acids. Volatile bases, chitin, and nucleic acids 

 account for the remainder of the nitrogen. Krill exhibits a high 

 content (46%) of the essential amino acids, thus making krill an ex- 

 tremely rich source of amino acids. 



Fat. — The literature reports that although the amount of fat in 

 krill will vary with season, the composition of krill fat seems to re- 

 main quite constant. Krill fat has a high content of complex 

 (phospho) lipids (50%), about 30-40% neutral fats (glycerides) and 

 about 8% unsaponifiable fat. Unlike other Antarctic 

 zooplankters, krill contains no waxes during the winter period and 

 probably feeds on detritus in the absence of primary production 

 (algae). According to Grantham (1977), about 70% of the fatty 

 acids are unsaturated with the three essential fatty acids — linoleic, 

 linolenic, and arachidonic — totaling about 5%. 



Vitamins. — Significant amounts of vitamin A and the B com- 

 plex group occur in krill with lesser amounts of E and D. Astaxan- 

 thin, the vitamin A precursor, is found to be high in the ex- 

 oskeleton and is particularly rich in the eyes. The characteristic col- 

 or of krill is due to the presence of this pigment. 



Minerals. — Krill contains 28 elements in its mineral composition 

 and is a particularly rich source of calcium, iron, magnesium, and 

 phosphorus. Fluoride has been reported present by Bykov (1975) 

 but Soevik and Braekkan (1979) reported that values for fluoride 

 in krill greatly exceed the upper permissible limit of 100 mg/kg 

 calculated as sodium fluoride established by the U.S. Food and 

 Drug Administration (FDA) for fish protein concentrate (FPC) in 

 1967. They conclude that "The present values for fluoride in krill 

 exceed this limit by more than seven times for the freeze dried and 

 extracted meat, and 24 times for the entire shellfish. This would 

 make krill in any form, even peeled, fail to comply with re- 

 quirements for human consumption." 



This warning may not be applicable because there is an essential 

 difference between krill and FPC. The latter is a highly concen- 

 trated processed fish product arrived at by sophisticated chemical 

 processes. In its most desirable form of tail meat, krill is a naturally 

 occurring crustacean with no added fluoride within the meaning of 

 the Federal Food, Drug and Cosmetic Act. In mid- 1981 the FDA 

 announced that it had decided that the edible tail meat of krill 

 would be regarded as a food and not a food additive. It also stated 

 that the amount of fluoride (14 ppm) in krill did not render the krill 

 injurious to health. 



Calorific value. — The reported literature values for the prox- 

 imate composition of krill have been concerned with whole krill 

 rather than the edible tail meat. Chekunova and Rynkova (1974) 

 have determined that juvenile and adult krill have calorific values 

 of 1.0 and 1.1 kcal/g wet weight, respectively. 



Chitin. — According to Mauchline and Fisher (1969), the ex- 

 oskeleton of krill accounts for about 10% of its dry weight. The 

 high content of chitin — about 40% of the dry weight (Yanase 

 1975) — makes chitin a potentially valuable byproduct. 



Autolytic Degradation of Whole Krill 



Krill is one of the most perishable of marine products owing to 

 the presence of very active enzymes which initiate several forms of 

 degradation including rapid and severe autolysis. This is somewhat 

 noteworthy in view of the generally low temperature conditions 

 that prevail during the catching period. Mean air temperature in 

 the areas most likely to be fished in January is about 5 °C (41 °F). 

 Lagunov et al. (1973) stated that at a storage temperature of 

 5 °-7 °C the volatile base nitrogen content increases from 5-6 mg % 

 to 17 mg % in 24 h and accelerates to 66 mg % in 72 h. Accompa- 

 nying this change are a pronounced textural change from firm to 

 flaccid, high drip losses, and sensory depreciation. When stored 

 more than 40 cm deep at 5°-7°C (41 °-45°F), the internal organs 

 are ruptured and release the highly active enzymes. Even shallow 

 heaps of krill stored exposed on deck will generate significant 

 heating. 



At relatively cool temperatures of about 10 °C (50 °F) in a matter 

 of a few hours on deck, various discoloration patterns develop. 

 The krill become pale in color and lose their usual crustacean 

 transparency; they soon change to a yellow-grayish color accom- 

 panied by what is termed "black spot," in the shrimp industry, of 

 the tissue beneath the exoskeleton of both the abdomen and 

 cephalothorax. The color degradation can even affect the end pro- 

 duct. Another fairly common color change is that occasioned by 

 the incomplete digestion of chlorophyll-containing phytoplankton 

 in the stomach or filtering apparatus. The result is a greenish tinge 

 imparted to the final product in addition to a disagreeable flavor 

 change (Grantham 1977). 



If these were not enough, there is also a microbiological transi- 

 tion that must be reckoned with. Like most marine fish, krill have 

 a low bacterial content at the moment of catching but soon afford 

 an excellent medium for bacterial growth once the krill die and are 

 landed on deck or stored. Concommitant with this normal 

 bacterial buildup in krill, Sieburth (1959, 1960, 1961) has found 

 that krill feeding upon certain species of phytoplankton contain 

 an antibacterial component that has been identified as acrylic acid. 

 At present, not enough is known of this antibacterial agent to take 

 advantage of its apparent unusual properties. 



To most fishery people, the storage temperatures mentioned 

 above (5°-7°C) seem unduly high in an Antarctic environment 

 when compared with normal North Atlantic fishery operations. 

 Under good conditions of operation of the latter, gutted fish are 

 stored in ice in such a fashion that fish temperatures of < 2 °C are 

 soon achieved and maintained or even lowered before discharge of 

 the cargo. Polish investigators have tried holding krill at 0°C and 

 < 1°C, but, although some extension of storage life was obtained, 

 the amount of extended storage life was not considered worth the 

 effort. 



International Efforts and Food Product Forms 



The nations that have worked with krill as a potential food 

 source have generally agreed that efforts should be made to use 

 krill as a food for direct human consumption rather than as feed 

 for animals. The conversion of krill presents technological pro- 

 blems of a serious nature owing to the small size of the animal and 

 the possession of active enzymes which cause rapid autolysis. 



It is agreed among the Russian, Polish, and West German in- 

 vestigators that krill should not be held at 10 °C (50 °F) for more 

 than an hour before processing or held longer than 3 h at 0°-7°C 

 (32 °-45 °F). Any increase in either temperature or holding period 

 results in undesirable autolysis. Krill should be piled < 30 cm (12 in) 



