Apple pectin as a novel prebiotic substance, that helps the intestinal microbiota....

We know the proverb "An apple a day keeps the doctor away" because of the fact that apple has been  addressing the health effects of the fruit, dates from 19th century. Interestingly apples have shown reduce the risk of  colon cancer, prostate cancer and lung cancer.Compared to many other fruits and vegetables, apples contain relatively low amounts of Vitamin C, but are rich source of other antioxidants.  The fiber content, while less than in most other fruits, helps regulate bowel movements and may thus reduce the risk of colon cancer. They may also help with heart disease, weight loss,  and controlling cholesterol, as they do not have any cholesterol, have fiber, which reduces cholesterol by preventing re absorption, and are bulky for their caloric content like most fruits and vegetables . There is  in vitro evidence that  phenolic compounds in apples (quercetin, epicatechin, and procyanidin B2) are  cancer-protective and  also demonstrate antioxidant activity.

Apples can be canned or juiced and the juice can be fermented to make apple cider (non-alcoholic, sweet cider) and cider (alcoholic, hard cider), ciderkin, and vinegar. Alcoholic beverages are produced such as applejack (beverage) and Calvados.  Apple wine can also be made. Pectin is also produced. 

Now microbiologists at the University of Denmark's National Food Institute,  tested the effect of apple consumption by feeding rats a diet of whole apples as well as apple-derived products such as apple juice and puree. The researchers then checked the bacteria in the guts of the rats to see if consuming apples affected levels of "friendly" bacteria, which are beneficial for digestive health and may reduce the risk of some diseases. Researchers found that rats eating a diet high in pectin, a component of dietary fiber in apples, had increased amounts of certain bacteria that may improve intestinal health.

As per the claim by the researchers, consuming apples affected levels of "friendly" bacteria, (bacteria that are beneficial for digestive health) and there by  reduce the risk of some diseases. And bacteria help produce short-chain fatty acids that provide ideal pH conditions for ensuring a beneficial balance of microorganisms. They also produce butyrate, which is an important fuel for the cells of the intestinal wall. Interestingly, consumption of apple pectin (7% in the diet) increases the population of butyrate and beta-glucuronidase producing Clostridiales, and decreases the population of specific species within the Bacteroidetes group in the rat gut. Similar changes were not caused by consumption of whole apples, apple juice, puree or pomace....

Ref : http://www.biomedcentral.com/content/pdf/1471-2180-10-13.pdf