Effect of Olive Leaf Extracts on the Growth and Metabolism of Two Probiotic Bacteria of Intestinal Origin

Abstract

The increase in viable cell numbers and the production of Short-Chain Fatty Acids (SCFA) by Bifidobacterium infantis and lactobacillus acidophilus-both of human intestinal origin-were measured over 16 h at 37^oC in reconstituted skim-milk (100 g L^-1) and skim-milk with one of three olive leaf extracts (water, ethanolic and methanolic extracts). The olive leaves were collected from a well known olive tree variety in Jordan (Nabali). All the three olive leaf extracts increased cell counts over the control with no extracts and the final values for SCFA, especially acetic acid secreted by L. acidophilus (1.84 gL^-1), were significantly higher than those observed in milk alone. The ethanolic extract of olive leaves showed highest effect on cell count and SCFA production for both bacterial species. It is proposed that the polyphenol compounds in olive leaf extracts were responsible for the stimulation of probiotic bacteria growth and metabolism and that olive leaf extracts ingested in human diet might have the same effect on desirable components of the intestinal microflora. The results of the research will be used in functional food development and food preservation purposes. This research will create a market potential for a range of new health based food to maintain optimal human health. This research is the first attempt to produce fermented milk with olive leaf extracts.