# Rheological, Textural, and Sensorial Characterization of Walnut Butter
## 1 Introduction  
Today, consumer awareness of unhealthy eating habits, especially the lack of natural foods, or the consumption of foods rich in saturated fats, food additives, salt, and/or sugars is observed in most societies [1]. In recent years, herbal-based butter (nut and seed butter) has been widely consumed by people around the world. Peanut butter is the most widely consumed plant-based butter [2, 3], but countless varieties of butter have been developed ( soybean butter, almond butter, pistachio butter, cashew butter, sunflower seed butter, pumpkin seed butter, and sesame butter, etc.) from various types of nuts and seeds, which are a good source of protein, fiber, essential fatty acids and other nutrients [4]. The development of new walnut spreads could make a significant contribution to the daily diet and present a healthier snack to consumers as they become more interested in the health, taste, and quality of food ingredients. Undoubtedly, the interest in healthy foods that meet the nutritional requirements of consumers has also brought awareness of the need for new functional products on the market. Walnut (_Juglans regia_ L.) is one of the main nut crops in the world, which grows in large areas in northern Bukovina (Suceava Romania). Walnuts have been harvested since prehistoric times [5], and are an important part of regular diet; the use of walnuts in bakeries and pastries is a part of cultural identity [6, 7]. The use of walnuts, as an important part of our daily food, has its roots in food traditions [6]. Walnuts can be eaten raw, fried, andsalted, added to dairy products, or can be sprinkled on salads, and desserts, especially walnut ice cream. Walnut desserts have been appreciated for thousands of years. One of the widespread applications of walnuts is their use in the confectionery industry by adding them to biscuits, cakes, and desserts. Walnuts are rich sources of polyunsaturated lipids (a perfect balance of polyunsaturatedated fatty acids (PUFA) n-6:n-3 (4:1)), proteins, dietary fiber, carbohydrates, minerals, especially potassium, magnesium, calcium, and other micronutrients; therefore, they are ingredients in different diets recommended for the prevention of aging and age-related diseases [7; 8; 9]. Nowadays, walnuts are one of the most important sources of polyphenols; the main polyphenol in nuts is pedunculagin, an ellagitannins. Ellagitannins possess antioxidant and anti-inflammatory bioactivity with a role against the onset of disease, including cancer, cardiovascular and neurodegenerative diseases [10]. Walnuts roasted with hot air to improve the sensory properties, develop the characteristic taste and aromas as well as improve the texture, have become popular snacks, and are a valuable raw material in the food industry [11]. For example, studies have revealed that the optimum roasting conditions for walnuts are 130-150 \({}^{\circ}\)C for 15-20 min [12], or in other research taking into account the variations of the nutritional qualities, the heat drying of 105 \({}^{\circ}\)C was recommended as an optimal process for walnut drying, in which protein, soluble sugar, carbohydrate, and minerals showed the highest values [13]. Walnuts can be used as spreadable pasta by people who suffer from peanut allergy. Walnut-based pasta is obtained by roasting and grinding the kernels. Walnut butter is one of the best alternatives to milk butter; it is one of the most sustainable foods; and it is environmentally friendly, with health-promoting effects; therefore, many studies have reported its role in preventing many diseases, such as diabetes 2 [14; 15], hypercholesterolemia [14], obesity [16] and coronary heart disease [17]. The effects of different levels of emulsifying agents (mono-diglyceride and lecithin at 0, 0.5, and 1.5% \(w/w\) levels) on the rheological texture homogeneity (GLCMs and fractal dimension) and stability of walnut butter have been studied by [PERSON] et al. [18].