## 1 Introduction  
Oyster mushrooms (_Pleurotus ostreatus_) are the second most widely cultivated mushrooms in the world [1, 2]. They have attracted increased attention due to their nutritional value and delicious taste [3]. Oyster mushrooms contain over 13 vitamins, such as Vitamin B groups and Vitamin C. It is worth mentioning that Vitamin B3 content in oyster mushroom is 5-10 times higher compared to any other vegetable, and calcium, phosphorus, and iron (with high bioavailability) content is approximately double the amount available in beef and pork meat [4]. In addition, mushrooms have a high percentage of high-quality proteins, containing all essential amino acids required by humans [2]. Therefore, mushrooms are considered a good substitute for high-protein foods that are also known as \"meat free\" (meat analogues), such as beef/chicken patties, nuggets, and sausages [5, 6, 7]. On the other hand, edible mushrooms degrade very quickly and lose their quality after harvest, mainly due to their high moisture content (85-95%, wet basis) which fosters microbial activities, high respiration rate, vulnerable texture, and high enzymatic activities [2, 8]. The short shelf life of mushrooms causes difficulties in their distribution and marketing as fresh products, limits the amount of consumption, and has economic consequences. Generally, fresh oyster mushrooms can be stored for 8-11 days at 0 \({}^{\circ}\)C, 4-6 days at 5 \({}^{\circ}\)C, 2-3 days at 10 \({}^{\circ}\)C, and 1-2 days at 20 \({}^{\circ}\)C [2; 3]. Dehydration, as a sole technique or in combination with other methods, is one of the most common treatments to extend the shelf life of foods. Techniques that are commonly used to produce dried mushrooms include conventional hot air drying, solar drying, sun-drying, oven drying, and microwave drying [2; 3; 8]. However, these methods require high temperatures and long processing times, resulting in alterations in the color and nutritional value of the final product. An alternative, mild dehydration method is osmotic dehydration (OD). OD involves the immersion of food in hypertonic solutions (composed of sugars, salts, or other solutes), leading to: (a) the removal of water from samples into osmotic solution, (b) the import of osmotic solutes from osmotic solution into the samples, and (c) the transfer of certain soluble solids from the food sample (including sugar, phenolic compounds, and minerals) to the hypertonic solution [9; 10; 11]. The driving force of mass transfer is the concentration difference on either side of the food cell membrane [12]. The mass transfer phenomena stop when chemical balance between the mediums is reached [13]. Osmotic dehydration helps to extend the shelf life of products by removing water, which inhibits microbial growth and enzymatic reactions [11]. The effectiveness of osmotic dehydration is influenced by three crucial factors: temperature, osmosis time, and osmotic solution concentration. Temperature plays a significant role in osmotic dehydration as it directly impacts the rate of water diffusion. Although higher temperatures lead to faster water extraction from the food material, excessively elevated temperatures can cause undesirable textural and color changes, so careful control of the process temperature is essential. For immersion time, a longer duration of osmosis allows for deeper penetration of the osmotic solution into the food, resulting in increased water loss and better preservation. Nevertheless, an excessively extended osmosis time might lead to excessive solutes uptake, altering the taste of the product. Lastly, the concentration of the osmotic solution significantly influences the process. A higher concentration of solutes creates a steeper osmotic pressure, driving more water out of the food material. However, using extremely concentrated solutions may cause a reverse osmotic effect, causing water uptake instead of removal [13; 14; 15].