CHITIN AS A FOOD COMPONENT
6.2 CHITIN AS A FOOD COMPONENT
Crustaceans, insects, rodents, frogs, snails, earthworms, spiders, scorpions, centi- pedes, and millipedes have been used as food sources for millennia. Insects utilized in this fashion are more extensive than one can imagine (Table 6.1). One usually thinks only of ants, bees, wasps, beetles, and caterpillars, commonly referred to as “bush tucker” by the Australian aborigines. A closer examination of world insect consumption shows that more than 2000 edible species have been utilized as a food source to date, although this is stated to be underreported, and continued research will increase this number considerably. 17–23 Nevertheless, it should be said that of the 15 million plants, animals, and microbes on Earth, more than 90% of the world’s food supply comes from just 15 crop species and 8 livestock species.
What is important is that chitinases are present in plant foods, and that human and bacterial chitinolytic enzymes occur in the human digestive apparatus. The bibliographic research allows confirmation of the presence of chitinolytic enzymes
Functional Food Carbohydrates
TABLE 6.1 Consumption of Insects as Food in the World
Most Popular Insects Cooked and Eaten
Africa
35 Gonimbrasia belina (grub) Central and South America
23 Rhynchophorus spp. (snout beetle) Aegiale hesperiaris (butterfly) Atta spp. (ant)
Asia
18 Locusta spp. Bombyx mori (silkworm)
Australia
14 Rhynchophorus ferrugineus papuanus
in a lot of plant organs and the making of a list of the vegetables and fruits that man uses that could help digest chitin. Although the level of chitinases is often correlated to the presence of stress, like infections, these enzymes also occur in healthy plant tissue and, above all, in fruits under maturation, which are most often used in human nutrition. 23–25
In the excreta of healthy people there is at least a bacterial species able to hydrolyze chitin to N-acetyl glucosamine. Clostridium paraputrificum in the human colon is able to synthesize and secrete chitinases and beta-N-acetyl glucosaminidase, which could take part in the digestion of chitin. Similarly, chitotriosidase, a chitinase produced by activated macrophages, is able to hydrolyze chitin 26–30 (see below).
An inherited deficiency in chitotriosidase activity is frequently reported in plasma of Caucasian subjects, whereas in the African population this deficiency is rare. The study of Musumeci et al. 31 compares chitotriosidase activity in colostrum of 53 African women and 50 Caucasian women. Elevated chitotriosidase was found in the colostrum of African women on the first day after delivery (1230 ± 662 nmol/ml h –1 ), which decreased with time. The chitotriosidase activity on the first day after delivery in the colostrum of Caucasian women, however, was significantly lower (293 ± 74 nmol/ml h –1 ) and decreased to 25 ± 20 and 22 ± 19 nmol/ml h –1 on the second and third days, respectively. The chitotriosidase activity in the plasma of African women was also higher (101 ± 80 nmol/ml h –1 ) than that of Caucasian women (46 ± 16 nmol//ml h –1 ), but no correlation was found between the plasma and colostrum activities. The elevated chitotriosidase activity in the colostrum of African women suggests the presence of activated macrophages in human milk, consistent with the genetic characteristics of the African population and their chitin- eating habits. Actually, a chitin-rich diet induces the secretion of human chitinases.
Chitosan is present in certain fermented cheeses in Northern Europe, and high glucosamine contents have been documented in Oriental fermented foods. 32,33