Food chemistry/Food-derived bioactive peptides

Introduction
Many food proteins are sources for peptides that show biological activity. This activity can be divided into effects on human health and effects on stability of food products.

Obtention of peptides
These proteins can be obtained from animal sources such as milk, meat, fish, egg, or from plants like wheat, soy, rice and other grains. Bioactive peptides can be produced from precursor proteins in several ways:
 * Enzymatic hydrolysis by digestive enzymes. This process occurs naturally every time we eat food or it can be done in vitro with purified enzymes.
 * Fermentation with proteolytic starter cultures.
 * Proteolysis by enzymes derived from microorganisms or plants.

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Effects on health
The effects that these peptides can produce on health include reduction in blood pressure, reduction of cholesterol blood levels, antithrombotic properties, and enhancement of mineral absorption.

Reduction of blood pressure
Some peptides have the property of inhibiting the angiotensin I-converting enzyme (ACE) which catalyzes the conversion of angiotensin I to a potent vasoconstrictor angiotensin II that participates in the regulation of blood pressure. A great number of ACE inhibitory peptides have been isolated from the digestion of various food proteins such as soybean, sunflower, rice, corn, broccoli, wheat, garlic, spinach and wine.

Mineral absorption
It was found that milk proteins can provide peptides that enhance calcium and phosphate bioavailability.

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Effects on food stability
In relation to food stability, some peptides show antioxidant and antimicrobial properties.

Antioxidant properties
Some peptides have a preventing effect on the degradation of essential lipids. The products of lipid oxidation produce alteration of taste and flavour in food products. Suetsuna et al. (2002) found these peptides in wheat gluten. Saiga et al. (2003) also isolated peptides from porcine myofibrillar proteins by protease treatment. The importance of these molecules is to reduce the use of synthetic compounds which are under regulation and replace them by natural compounds.

Antimicrobial properties
There are peptides which affect the growth of bacteria, yeasts and fungi. Many of them were isolated from milk and egg. ---

Conclusions
The discovery of new properties of food-derived peptides gives them the possibility of being used as food ingredients providing health benefits to consumers. This information is also of importance for the study of new sources for peptides. ---