# Physicochemical Properties of Apple Purees and Peel Extract for Potential Use in Pastry Products
## 1 Introduction  
In recent years, a very large number of cases of obesity (over 1 billion) have been registered. Also, the number of type II diabetes cases is increasing (over 300 million). The main cause of obesity is the energy imbalance, more precisely the imbalance between the calories consumed and those burned, and the main causes of type II diabetes are: obesity and excessive consumption of sucrose [1, 2, 3]. Lately, the consumption of sugar has experienced a significant increase. While our ancestors relied mainly on natural sugars from fruit and honey, today sugar is an added ingredient in most processed foods [4]. In addition to the natural sugar present in foods such as grains, fruits, vegetables and milk, manufacturers add sugar to baked goods, both to enhance the sweet taste and for the multiple roles it plays (in terms of texture, flavor, color and preservation) [5]. Considering the current food trends, it is necessary to implement some preventive measures that involve both educating the population in order to choose a healthy diet, as well as constraining producers in order to reduce and substitute the amount of sugar in food products [2, 6, 7, 8, 9]. These measures represent a real challenge, both in educating the consumer who, most of the time, chooses food products according to their organoleptic properties, as well as in the production of foods with low sugar content, but which present sensory characteristics accepted by the consumer [2, 6, 7, 8, 9]. Pastry products are foods that contain large amounts of sucrose, whichmakes them calorie dense and prone to overconsumption. An alternative in reducing the sugar in these products could be replacing sugar with substitutes, such as: apple puree or other fruits, Stevia, inulin, date syrup or powder, oligofructose, apple pomace, Nypa fructicans syrup, grape syrup or polyols [10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25]. The apple (Malus domestic) is a widely consumed fruit throughout the world, being one of the most cultivated fruit species and being in the top five most consumed fruits [26; 27]. They are preferred by consumers due to their flavor and high nutritional value, being rich in vitamins, minerals and phenolic compounds [28; 29; 30]. Properly stored, these can be available throughout the year both in its biological form and in the form of juices, purees, cider, frozen or dried slices [28; 31; 32]. The processing of apples implies the loss of 25% of their mass; thus, parts such as pulp, peel and seeds are thrown away [31; 33]. Thus, the use of apple pures in the production of food products represents an alternative both to avoid waste and to improve the nutritional value of the finished products [24; 25; 31; 34; 35; 36]. Apples attract the attention of the scientific community through their content in bioactive compounds, such as phenolic compounds (phenolic acids, flavonoids) [26]. The presence and concentration of phenolic compounds depends on the anatomical part of the apple, species, storage, environment, and degree of ripening. The main phenolic acids in apples are the caffe acid and the p-coumaric acid, and the most important flavonoids are: quercetin, catechchin, epicatechin [37; 32]. Due to their high content of hydroxyl groups and high antioxidant capacity, phenolic compounds play a very important role in the human body, disrupting oxidation processes. By providing electrons separated from the phenol group or hydrogen atoms, polyphenols prevent the production of free radicals [29]. The high content of antioxidants in apples can prevent the occurrence of diseases caused by oxidative stress (cardiovascular diseases, asthma, diabetes, cancer) [26; 27; 29; 38; 39]. Also, apples are an important source of mineral elements, in the composition of which there are both macroelements (Na, Mg, Ca, K) and microelements (Cu, Mn, Zn, Fe) [40; 41]. During the storage of apples, numerous physical, chemical and biochemical changes take place.