# Production of Vegan Ice Cream: Enrichment with Fermented Hazelnut Cake
## 1 Introduction  
Ice cream is a frozen dairy dessert traditionally made from milk, cream, sugar, and stabilizers, with possible inclusions of eggs, fruits, nuts, or flavorings [1]. Its origins trace back to ancient China, where snow and ice were mixed with fruit and honey, while Persian empires developed sharbat, a chilled dessert that later influenced Italian sorbetto [2]. The modern iteration emerged in 17 th-century Europe, with industrial production beginning inthe 19 th century following advances in refrigeration and homogenization. Global consumption exceeds 18 billion liters annually, led by the U.S., Australia, and New Zealand, while artisanal varieties--such as Italian gelato (denser and lower in fat), Turkish dondurma--Maras (chewy, with salep-- a plant-based emulsifier), and Japanese mochi ice cream (ricewrapped)--highlight cultural adaptations. Recent trends focus on functional ice creams fortified with probiotics, plant proteins, or reduced sugar to align with a health-conscious demand [3]. However, ice cream is a globally consumed dairy-based dessert, and growing consumer demand for plant-based alternatives has driven innovation in vegan ice cream formulations [4]. Vegan ice cream is a plant-based frozen dessert that replicates the sensory properties of conventional dairy ice cream by utilizing non-animal-derived ingredients such as nut, legume, grain, or seed milks, combined with plant-based fats, sweeteners, and stabilizers [4]. While early iterations date back to the 19 th century with sorbets and coconut-based formulations, the modern vegan ice cream industry emerged in the late 20 th century alongside rising lactose intolerance awareness and ethical consumerism [5; 6]. Nutritionally, vegan ice cream typically contains comparable energy density (180-350 kcal/100 g) to dairy versions but often provides higher fiber, unsaturated fats, and bioactive compounds (e.g., polyphenols and tocopherols) from plant sources, although the protein content varies significantly based on the base ingredients [7]. Common plant-based milks used in production include almond, soy, coconut, oat, and cashew, with newer innovations leveraging pea, hemp, and upcycled byproducts (e.g., fermented hazelnut cake) to enhance functionality [8; 9]. Global consumption reached $1.2 billion in 2023, with North America and Europe dominating the market, while Asia-Pacific shows the fastest growth due to rising flexitarian diets [10]. Future projections estimate a 12.8% CAGR (2024-2032), driven by advances in fermentation, protein texturization, and sustainable ingredient sourcing (e.g., microalgae fats and upcycled food waste) to improve sensory and nutritional profiles [11]. Regulatory frameworks and clean-label demands are expected to further shape product development, positioning vegan ice cream as a mainstream choice in the frozen dessert sector. Traditional dairy substitutes, such as almond, soy, and coconut milk, are widely used in vegan ice cream production, but there is increasing interest in upcycling agro-industrial byproducts to enhance nutritional and functional properties [9; 12]. Hazelnut cake, a byproduct of hazelnut oil extraction, is rich in proteins, fibers, and bioactive compounds but remains underutilized despite its potential [13]. Solid-state fermentation (SSF) of oilseed or nut cakes--a byproduct of oil extraction--utilizes microbial cultures (e.g., _Aspergillus oryzae_ and _Rhizopus oligosporus_) to enhance their nutritional and functional properties. SSF occurs under low-moisture conditions, enabling fungi or bacteria to hydrolyze anti-nutritional factors (e.g., phytates and tannins) while increasing protein digestibility, bioactive peptides, and phenolic compounds [14]. Fermented cakes exhibit elevated antioxidant capacity (via free radical scavenging assays), angiotensin-converting enzyme (ACE)-inhibitory activity (antihypertensive potential), and prebiotic oligosaccharides due to microbial enzymatic action [15].