Article Physicochemical characteristics, oxidative stability, and micro- biological properties of blended French sauce with olive and soybean oils and augmented with olive leaf polyphenolic extract obtained via ultrasound-assisted extraction Mohammad Amin Aliyari 1 , Karamatollah Rezaei 1 * 1 Department of Food Science, Engineering, and Technology, College of Agriculture & Natural Resources, Uni- versity of Tehran, Karaj Campus, Iran. E-mail: amin1374aliyari@gmail.com 1 * Department of Food Science, Engineering, and Technology, College of Agriculture & Natural Resources, Uni- versity of Tehran, Karaj Campus, Iran. Correspondence: E-mail: krezaee@ut.ac.ir; Tel.: +982632235124 Abstract: This study was carried out in three phases. During the first stage, the physicochemical properties of French sauce prepared from different blends of soybean and olive oils were evaluated. In the second stage, the oxidative stability of the optimum sauce sample from the first stage enriched with various amounts of olive leaf polyphenolic extract (OLE) (obtained via ultrasound-assisted extraction) was investigated over 90 days of storage. During the third stage, the microbiological and sensory properties of the samples containing the optimum amounts of OLE, as a substitution for the synthetic preservatives, were studied. According to the results, addition of olive oil at higher levels (75 and 100%) could affect the physicochemical properties of the sauce as compared to the control sample. It was also found that the addition of olive oil (up to 50%) would not significantly impact the sauce properties. Regarding the OLE enrichment in the samples, it was found that high levels of OLE could improve the oxidative stability of the samples. Based on the results of the experiments in the third phase, it was found that OLE could be used as a preservative instead of the commercial ones. Overall, this study suggests the potential use of olive oil and olive leaf extract in the prepara- tion of French sauce to boost its nutritional value and its stability. Keywords: Functional Food; Sauce; Olive Oil; Olive Leaf; Polyphenolic Compounds 1. Introduction Sauces and salad dressings are oil in water (O/W) emulsions that have drawn the attention of the consumers for their daily diets. Sauces are being used to improve the flavor, taste, and appearance of many food products and among them French sauce is one of the most known ones [1]. Generally, these types of products are called cold-sauces as any amount of heating treatments would result in an emulsion-breakdown [2]. Increasing demand for the health-promoting prod- ucts has led salads to get special attention as healthy food products. This, in turn, has promoted the use of sauces as one of the main commodities in our daily diets. French sauce has been a matter of interest among scientists. For instance, Rasmussen et al. [3] showed the potential use of honey as a good substitute for EDTA and commercial sweeteners. In an another study, de Melo et al. [4] evaluated the stability and nutritional index of French sauce samples with the use of mannoprotein from spent brewer's yeast. A typical French sauce usually consists of egg yolk, vinegar, oil, and tomato paste. In addition, several ingredients such as paprika, mustard, and garlic powder are needed as the main participants for sauces’ specific taste and flavor. Moreover, texturizing agents are normally used to form the consistency of the sauce [5]. In sauces’ formulation, the type and nature of the used oil are very important. In sauces and dressings oil phase plays a vital role in the stability and general appearance of them. Additionally, the nutritional value of sauces can be considered as a direct function of their oil phase. Using oils with high amounts of saturated fatty acids can easily lead to several health problems such as obesity, cardiovascular disease, etc. [ 6]. Olive oil is a source of beneficial components such as polyphenolics, hydrocarbons, sterols, pigments, volatile com- pounds, vitamins, and minerals [7]. Olive oil is relatively resistant to oxidation because of its noticeable amount of Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 23 April 2021 © 2021 by the author(s). Distributed under a Creative Commons CC BY license.