Acid Content in Soft Drinks and Juices by Endpoint Titration

This application note presents the determination of acid content in fruit beverages such as juices and pulp by the endpoint titration method using an EasyPlus titrator with sodium hydroxide as the titrant.

Acidified and Acidic Foods

According to the US FDA, acidified foods are categorized as low-acid foods with pH values of 4.6 to 6.9. In the case of acidic foods, food-grade acid is added to reduce the pH to < 4.6, or they naturally have a pH of less than 4.6.
 

Organic Acids in Fruit Juices

Fruit juices contain organic acids such as citric, malic, lactic, tartaric, and acetic acids, which either occur naturally in the fruits or are added artificially. In addition, inorganic acids such as phosphoric and carbonic acids are also present. The appropriate acidity enhances the sensorial, nutritional, and microbiological quality of the beverages.
 

Why Determine Acidity in Food?

The acids present are an indicator of the degree of maturity. Their influence affects the flavor (i.e., tartness), color, stability (shelf life), and quality level. They also help in microbial growth retardation. Besides affecting the quality and shelf life, acidity is a relevant factor for the consumer as it contributes to dental erosion, acid reflux in the stomach, etc. Hence, it is essential to determine the acid content in juices and beverages.
 

How to Determine Acidity in Food?

To determine the acid content, the pH of the beverage is determined by titrating it against a base. The titration is monitored by potentiometric measurement with a pH sensor and terminated at a pre-defined pH, the endpoint (EP).