Crab and grapes (wine)

Crabs

Crabs are high in protein, vitamins, minerals and low in saturated fat. Crabs contain high omega-3 which can help to decrease the triglyceride and blood pressure. In directly, the crabs are able to reduce the risk of heart disease, inflammation, enhance immune system and lower certain types of cancer. In addition, crabs contains high level of vitamin B12 which required for healthy nerve system. (Kristie Leong MD, 2009)

Grapes (wine)

Grapes contain tannic acid especially in the skin and seeds. There are 2 types of tannic acid, condensed tannins and hydrolysable tannins. Tannic acids from the grape are condensed tannins, which are polymers of proanthocyanidin monomers. Wine produce by the yeast fermentation of grapes contains high tannic acid. In the fermentation of red wine, grapes skin and seeds are not separated in the purpose to extract the colour from the skins. The tannic acid found in wine not only from the grapes. The oak wood barrels normally used to aging the wine also contain tannic acids. Tannic acid from the oak wood will leak or transfer into the wine, increasing the amount of tannic acid in wine. The tannic acid extracted from oak wood is hydrolysable tannins.

What happen if eat crab and wine together?

There are some articles that mentioned that crabs and wine eat together can cause diarrhea, nauseous, stomach pain, and vomiting. Tannin in wine will interact with the protein forming tannin-protein complexes. Tannin cause precipitation of protein and decrease the absorption of the protein by the body. This tannin-protein complex coagulum will accumulate in the stomach and cause stomach discomfort and stomach ache. In addition, if the crab contains metal elements, tannin will also react with the metal and may cause formation of stone over many years (admin, 2009). High level of tannic acid can decrease the feed intake, net metabolism energy and protein digestibility (Chung KT. et.al, 1998). According to Chung KT. et.al, the major effect of tannins is due to the decreased of efficiency in converting the absorbed nutrients to new body substances.

The Effect of eating Crabs and Wine (grapes) together

Interaction of tannin and protein.

Formation of tannin-protein complexes are based on the strong hydrophobic and hydrogen bond. Tannin contain phenolic group that act as an excellence hydrogen donor. When tannin interacts with protein, the phenolic group will form a strong hydrogen bond with the carboxyl group in protein. The bonding formed is specific and depend on the structure of the protein and tannin. (Antonello Cannas, 2009)

Characteristic of protein that affect the bonding:

1. Molecular size: the larger the molecular size, the stronger the bonds form.
2. Flexible of structure.
3. Amount of proline.

Characteristic of tannin that affect the bonding:

1. Molecular weight: higher the molecular weight, the stronger the bonds form.
2. High conformational mobility.
3. Chemical linkage.

However, in the condition of high pH, the phenolic group from tannin are ionized and protein has a negative net charge. The repulsion forces from the protein inhibit the process of precipitation. (Antonello Cannas, 2009)

References:


1. Admin, 2009. Too dangerous to drink tea immediately after a meal. Love Health [online] from: http://www.love-health.org/health_care/1083/

2. Antonello Cannas, 2009. Tannins: fascinating but sometimes dangerous molecules. Cornell University Department of Animal Science [online] from: http://www.ansci.cornell.edu/plants/toxicagents/tannin.html

3. Chung KT. et.al, 1998. Crit Rev Food Sci Nutr, 38(6):421-64. Pub Med [online] from: http://www.ncbi.nlm.nih.gov/pubmed/9759559

4. Kristie Leong MD, May 27, 2009. Four Delicious Health Benefits of Crab. Health Mad[online] from: http://www.healthmad.com/Nutrition/Four-Delicious-Health-Benefits-of-Crab.731715