## 1 Introduction  
In light of growing environmental concerns and the demand for sustainable food systems, the valorization of underutilized agri-food co-products--such as leaves, bark, and seed press cakes--has become a scientific and industrial priority. _Luffa cylindrica_ (L.), also known as sponge gourd or loofa, offers notable potential in this context due to its nutritional and functional attributes [1]. A climbing annual plant from the Cucurbitaceae family, _L. cylindrica_ is widely cultivated in subtropical regions, including South Asia, the Middle East, China, and the Americas [1,2]. Its young fruits, leaves, shoots, and flower buds are edible, while mature fruits develop a fibrous cellulose matrix that forms a natural sponge used in diverse applications such as exfoliation, cleaning, filtration, and packaging [2, 3, 4].  
The fruit of _Luffa cylindrica_ is a rich source of carbohydrates, vitamin C, and minerals, such as magnesium, calcium, sodium, potassium, iron, copper, zinc, and manganese [5], along with bioactive compounds like tannins, oxalates, phytic acid, saponins with immunomodulatory effects [6], glycosides, and flavonoids [7]. Its seeds are dull black, elliptical, and measure approximately 10-12 mm in length and 6-8 mm in width. They are edible and traditionally consumed roasted, similar to pumpkin seeds. Nutritionally, the seeds contain 33.55% protein, 29.51% carbohydrates, 22.17% fat, 6.47% fiber, and essential minerals (Ca, Zn, Mg, P) [8]. The seeds have demonstrated antiviral, anti-tumor, antioxidant, anti-inflammatory, and immunomodulatory activities [9]. Alkalase and tryptic protein hydrolyses support their potential in managing diabetes and hypertension [6]. The seed oil, dominated by linoleic acid (C18:2), exhibits antifungal, anti-inflammatory, and antitumor properties. It contains sterols (sitosterol, stigmasterol), tocopherols, phytol, hydrocarbons, glycolipids, and phospholipids, such as phosphatidylethanolamine [10], owing to its cytotoxicity toward skin cancer cells and its ability to inhibit protein synthesis in malignant tissues [11].  
Luffa seed oil is currently produced only on a small, artisanal scale in regions, such as Africa and China, with limited use in cosmetics, pharmaceuticals, and to a lesser extent, food; its production is not recorded in FAO statistics. The seed press cake, a protein- and fiber-rich byproduct of oil extraction, has traditionally been used in agriculture, cosmetics, or biofuel applications; however, its valorization for human nutrition remains largely unexplored [12]. Introducing luffa seed press cake into the food sector presents an innovative opportunity to develop new, sustainable protein sources. This aligns with the increasing consumer demand for plant-based diets driven by health, environmental, and ethical concerns, particularly among younger populations [13]. Meat analogues made from plant proteins, including flours, isolates, and textures, are being actively developed as alternatives to conventional meat, aiming to improve nutritional quality while reducing environmental and animal welfare impacts [14,15].  
The aim of this study was to explore the potential of _Luffa cylindrica_ seed press cake as a functional ingredient in meat substitute formulations by blending it with tapioca flour. A range of binary mixtures was evaluated to identify optimal proportions for application in alternative meat products. The focus was placed on the characterization of functional, rheological, and bioactive properties of the blends. This study is, to the best of our knowledge, the first to assess the combined techno-functional, viscometric, and antioxidant potential of _L. cylindrica_ seed press cake and tapioca flour systems. The findings support the valorization of this agro-industrial byproduct as a sustainable food ingredient.