Gluconic fermentation of fruit substrates is an innovative strategy to elaborate nonalcoholic beverages which has not been studied so far. Futhermore, it prevents food waste of perishable products like strawberries. Amino acids, biogenic amines and ammonium ion were evaluated after the fermentation of strawberry purée using Gluconobacter japonicus in submerged culture. The process was monitored with the determination of pH, total acidity, glucose, fructose and gluconic acid concentrations. The determination of nitrogen compounds was accomplished using a HPLC–UV method involving diethyl ethoxymethylenemalonate (DEEMM) as the derivatization agent. Most amino acids did not present significant changes, except for lysine and histidine, which increased their concentration in the final product. However, the principal component analysis was able to group the initial and final samples in different sets using the amino acids concentration as variables. Biogenic amines were not detected in the final samples, thus ensuring the safety of this product for human consumption.
Practical Applications
Because of the high level of competitiveness, the success of a new product requires the use of a raw material different from the traditionally used ones, and the application of innovative techniques of production. Strawberry is a fruit prized for its aroma and flavor. In addition, Spain is the fifth strawberry producer in the world, and consequently there are surpluses of second quality strawberries. This second quality fruit is generally discarded, involving large economic losses. These facts make strawberry a good candidate to be used as raw material for the production of fruit derived products. Hence, gluconic acid fermentation is an innovative way of transforming surplus strawberries into beverages which do not present glucose, as it is transformed into gluconic acid whilst keeping fructose as sweetener. Hence, the final product could be the principal substract to elaborate a new beverage which could be consumed by diabetics. Gluconic acid submerged fermentations of strawberry purée were carried out with Gluconobacter japonicus. Additionally, the amount of biogenic amines was assessed for food safety purposes.