Effect of probiotic Lactiplantibacillus plantarum strains on some properties of grapefruit juice and naringin

For citrus juices, especially grapefruit juice, bitterness is an important problem. In this study, some probiotic bacteria with naringinase enzyme activity (L. plantarum ACC 54, L. plantarum ACC 28, and L. plantarum 250) were added to grapefruit juice in order to reduce naringin, one of the most important bitterness components. Then, the physicochemical properties of grapefruit juice were investigated with changes in antioxidant activity, phenolic compounds and naringin amount. Improvements in the physicochemical properties of grapefruit juices were detected in the first three days of storage. Water-soluble dry matter, determined as Brix, was 9.13 on the first day of storage, and this amount decreased to 8.66 after 4 weeks of storage. Likewise, pH decreased from 3.58 to 3.11, and titratable acidity increased from 0.79% to 1.46%. Colour values were determined spectrophotometrically. During the storage period, IC value varied between 3.98 and 5.24, colour shade 1.27–1.29, red colour 32.18–32.54%, yellow colour 41.022–41.97%, and blue colour 26.80–25.49%. From the beginning of the storage period to the end of 4 weeks of storage, decreases were identified for DPPH• and ABTS•+ radicals, with the results changing from 16.41 to 31.98 and from 7.45 to 11.95, respectively. Total phenolic content was determined using the Folin-Ciocalteu reagent and values were 643.32–319.72 mg GAE/L from the beginning to the end of storage. The phenolic compound profile was determined by LC-MS/MS and the highest phenolic compound was found to be quinic acid (35768.88 ppb) in B25 at the end of the 4th week. The amount of naringin in grapefruit juice samples was determined by HPLC. The highest decrease (61.5%) in the amount of naringin in the samples was detected in B37 at the end of the 3rd day.