102 Principles of Food Science The gallbladder secretes bile, a greenish liquid, to further digest fats. Bile acts as an emulsifier, allowing water to mix with the fat molecules. This substance is made in the liver, stored in the gallbladder, and has a pH of about 8.4. Once food is adequately digested, nutrients are absorbed into the bloodstream. The body maintains the pH of the bloodstream at about 7.4. See 6-10. It is not possible for any food you eat to make the stomach more acidic. People who believe they have excess stomach acid may really have stomachs that are too full. A stomach that is too full can stretch the valve to the esophagus. This causes stomach acid to splash up into the esophagus, creating heartburn. People have long believed that excess acid would cause ulcers. Recent research has revealed that people In one to four hours after eating, the stomach empties the broken down food into the small intestine. The food is now a thick fluid called chyme. The majority of digestion and nutrient absorption takes place in the small intestine. The small intestine is a long tube divided into three parts called the duodenum, jejunum, and ileum. By the time chyme reaches the small intestine, it is in a semiliquid state. Once food leaves the stomach, the pH is rapidly raised to around 7.0 by the addition of pancreatic juice. Secretin, an intestinal hormone, stimulates the pancreas to release pancreatic juice that contains water and bicarbonate. Bicarbonate is a base needed to neutralize acidic stomach contents. This juice is a base with a pH of about 8.0. Digestion in the small intestine is also aided by the gallbladder. pH of the Digestive Tract Mouth (saliva, pH 6.5) Stomach (hydrochloric acid, pH 1.5-1.7) Gallbladder (bile, pH 8.4) Small intestine, pH 7.0 Pancreas (pancreatic juice, pH 8.0) Goodheart-Willcox Publisher 6-10 The pH of the digestive tract ranges from very acidic to slightly basic. Copyright Goodheart-Willcox Co., Inc.