Supercritical fluid extrusion of dairy and fruit products to generate GOS-enriched and nutritionally superior snack puffs

The consumption of ultra-processed snacks is often considered unhealthy because such foods generally are energy-dense with low nutritive value. They contain high levels of starch, fat, and sugar and low levels of essential nutrients such as fiber, protein, and bioactive compounds. Nutritionally balanced snack foods that cater to today’s on-the-go lifestyles and do not get in the way of better eating are in high demand. The present study aims to create nutritionally attractive extruded puffs by valorizing food manufacturing byproducts and to elucidate the uniqueness of hybrid extrusion processing and its effect on product quality parameters. Supercritical fluid extrusion (SCFX) was used to transform apple pomace, starch or dairy ingredient-based formulations into value-added products in a zero-waste system. Acid whey, a byproduct of yogurt and cheese manufacturing, was used in lieu of water in the extruder to mitigate environmental issues related to its disposal. The SCFX system was also used for in-process polymerization of galactose, sourced from lactose hydrolyzed skim milk powder (LHSMP), with lactose from milk protein concentrate (MPC) and acid whey sources to produce galacto-oligosaccharides (GOS), a prebiotic associated with various health benefits and making the product acceptable to lactose intolerant consumers. Analysis of the extruded puffs showed that a combination of pomace and dairy ingredients significantly improved the nutritional profile of the product, notably increasing the fiber (5.0 g/30 g serving), protein (13.6 g/30 g serving), bioactive compounds (phenolics 21.4 mg GAE/30 g and vitamin C 0.3 mg/30 g serving), minerals, and GOS (0.4 g/30 g serving) contents. A sensory acceptance test (n=91) showed that incorporation of fruit and dairy by-products in snacks either improved or maintained Just About Right (JAR) scores compared to Market Keto puffs. Overall, utilizing fruit pomace and acid whey in extruded products made by SCFX is not only able to generate nutritious and functional snacks with balanced nutrients profile, derived from inexpensive agro-food by-products feedstock, but also can help mitigate environmental and waste issues.