Physical–Chemical and Microbiological Characterisation of Blueberry By-Products (Vaccinium myrtillus L.) as Potential Food Ingredients

The production of blueberry juice generates large quantities of waste products such as skins, pulp and seeds. These by-products contain high levels of bioactive compounds and are suitable for use as functional ingredients in food systems. In this study three powdered products obtained from blueberry pomace—with skins and seeds, seedless, and with seeds—have been physically–chemically and microbiologically characterised as being the individual anthocyanins and phenolic compounds identified by HPLC-QTOF. Furthermore, to ensure product safety, the effect of a heat treatment at 90 °C for 30, 60, 90 and 120 min was also studied. The three products showed high concentrations of fibre, phosphorus, calcium and potassium. The two products with skins also showed high levels of anthocyanins, phenolic compounds and antioxidant activity. The product from seeds had the highest load of Aerobic Mesophilic Bacteria and Enterobacteriaceae whereas Bacillus spp. was found in the three products. Heat treatment at 90 °C for 90 min reduced the Aerobic Mesophilic Bacteria count below the detection limit. This treatment did not significantly affect the anthocyanin content, although some anthocyanins seemed to be more thermolabile than others, and increased the concentration of the phenolic acids and their derivatives. This study demonstrates the high nutritional and functional value of blueberry by-products, highlighting their potential as sustainable ingredients in the food industry and their viability after a heat treatment.