Aversion of Grape wine and Crab meat: June 2009

By Henry Chang 1000613589

Grapes are well known in every country through its sweetness and juiciness of the fruit. The fruit is largely planted in the European country as well as Mediterranean. Some of the country used grapes to produce wine by fermentation processes.

On the other hand, crabs, an exoskeleton crustaceans, which is delicious to be eaten while contain excellent source of high quality protein, vitamins, and minerals that are needed for good nutrition. Unfortunately crabs contain high cholesterol where by most of major health organization recommend a daily limit is 300mg.

Do you know when you eat crab with grape (wine) it will caused aversion or toxicity?

Lets Us Explore This

Tannins (generally referred as tannic acid), one kind of water-soluble polyphenols that normally present in the seed and skin of the plants or fruits. When the fermentation of grapes, the brewer normally blend all the part of grapes included seeds and skin, hence it increase the tannic acid content in the wine. Besides, the brewer kept the wine in the oak kegs and some tannin might migrate into the wine cause increases of tannins content. Tannins have been was discovered to be responsible on protein digestibility in experimental animals. However, recent articles and journals were indicated that the major effect of tannins was not due to their inhibition on food consumption or digestion but rather the reducing the efficiency in converting the absorbed nutrients to new body substances (Chung KT, Wong TY, Wei CI, Huang YW, Lin Y. 1998). Proteins, well known peptide chains that build up from residue of amino acids with peptide bonding and others bonds. In crabs or crab meat, they contain high amount of protein and others vitamin and minerals. Hence the aversion effects start when the protein in crabs meets tannins in grape specifically wine. The present of abundant protein and tannins will solidify and harden to produce insoluble and indigestible materials in the intestine. The production of the materials make one become nauseous, distends and painful stomach as well as vomiting (Wings, 2003).

How does the materials formed from tannins and protein?

Precipitation of proteins by tannins is at pH values near the isoelectric point of the protein. In solution at high pH, phenolic hydroxyls are ionized and proteins have net negative charges. In the conditions, precipitation does not occur because proteins exhibit repulsive forces. Strong complexes with tannins are formed by tannin-binding agents like polyvinylpyrrolidone (PVP) and polyethylen glycol (PEG), and protein denaturants like phenol. To have high protein affinity, tannins must be small enough to penetrate interfibrillar region of protein molecules but large enough to crosslink peptide chains at more than one point. HTs and PAs form tannin-protein complexes in similar manners. Proteins thus bound are generally resistant to attack by proteases and hence make the proteins indigestible. However, it is hypothesized that HTs may have a less damaging effect on protein digestion because these tannins may hydrolyze in the acidic gastric environment and release the bound proteins (M.A.Hayat, fourth edition). When soluble tannins interact with proteins, both soluble and insoluble complexes are formed. Soluble complexes are favored when protein concentration is in excess (fewer tannin attachment sites per each protein molecule). Soluble complexes represent an analytical problem because they do not precipitate and, thus, are difficult to measure. Insoluble complexes are formed when tannins are present in excess and form an hydrophobic outer layer in the complex surface.

They are 2 article link below that related to the aversion and toxicity breakout at china.
(Chinese Version)

http://gzsb.gog.com.cn/system/2006/09/03/001019456.shtml

http://www.fxrbs.com/news/dzjk/dzjk/20070911092452.htm

Special thank for references

Tannin and human health http://www.ncbi.nlm.nih.gov/pubmed/9759559

Blue crab nutrition facts http://www.bluecrab.info/nutrition.htm

Grape, Mark Rieger’s fruits Crops http://www.uga.edu/fruit/

Crabs, http://www.cyhaus.com/marine/crabs.htm

Food you can eat together, http://www.newsgd.com/english/goodtime/dinning/200304290625.htm

Principles and techniques of electron microscopy biological application 4^th edition pg 335, http://books.google.com/books?id=Z8aps369ELoC&printsec=frontcover&hl=zh-TW&source=gbs_v2_summary_r&cad=0

Tannic acid, http://www.phytochemicals.info/phytochemicals/tannic-acid.php

http://gzsb.gog.com.cn/system/2006/09/03/001019456.shtml