## 1 Introduction  
Apples (_Malus domestica_) are one of the most widely consumed fruits globally, with 93.1 million tonnes produced in 2021. In Europe, they represent 20% of the global production, with Portugal reporting 368,230 tonnes of apples produced. China is the largest producer with 45 million tonnes, followed by Turkey and the United States of America, both with 4.5 million tonnes produced [1]. Apples can be consumed in their natural state or processed into juice, jam, cider, and vinegar to minimize waste [2]. Apple puree (AP) is a common ingredient in many food items such as juices, beverages, fruit saucs, pie fillings, and infant foods. With its abundance of polyphenols, which are recognized for their antioxidant characteristics, and high fiber content, this food choice is both nutritious and beneficial for customers' health. Following the pressing of apples in the juice manufacturing process, the leftover solid residue, known as pomace, can make up 20-35% of the apple's original weight. This pomace is a combination of the apple's peel, core, seed, calyx, stem, and pulp [3]. Nevertheless, the quality of AP can vary based on genetics, storage, heating parameters, processing intensity, and refining. Consequently, it is essential to identify suitable and sustainable processing technologies that can guarantee food safety and preserve product quality [4]. Thermal processing has traditionally been employed in the food industry for AP pasteurization, with the aim of eliminating particular pathogenic bacteria including _Escherichia coli_, _Salmonella_ spp., and _Listeria monocytogenes_, which are responsible for foodborne illness outbreaks. Consequently, pasteurization diminishes the likelihood of contracting foodborne diseases and extends the shelf-life of AP and other apple-based products [5]. Before undergoing pasteurization, the AP is exposed to a technique called blanching, which involves a brief but significant thermal shock (about 100 \({}^{\circ}\)C for 30 s to 5 min) to deactivate enzymes associated with browning, such as polyphenol oxidase and peroxidase [6]. However, these thermal processes can frequently cause undesirable quality changes to the product such as vitamin loss, changes in texture or colour, and the development of off-flavours [7]. Recently, emergent processing technologies, such as ultrasound (US), pulsed electric field (PEF) and high-pressure processing (HPP), have attracted interest due to their ability to ensure food safety with minimal quality detrimental effects. Therefore, it is necessary to select the appropriate technology and processing conditions that can achieve, at least, the same microbial inactivation level comparable to that obtained for the conventional heat-based pasteurization methods to ensure food safety [8]. Moreover, in general, the shelf-life of both nonthermal (US, PEF and HPP-treated) and thermally pasteurized foods is comparable. Like thermally and HPP processed foods, PEF-treated products are usually stored refrigerated. In the application of US, food items are subjected to sonic waves at a frequency of approximately 20 kHz. These waves are generated either by probes or in a liquid bath. Ultrasound causes the formation of bubbles through pressure changes, and the subsequent collapse of these tiny bubbles leads to a localized rise in temperature and pressure. This phenomenon has a pasteurization effect without causing a substantial increase in overall temperature. PEF involves the administration of electric pulses (typically with a field strength ranging from 1 to 30 kV/cm in the food industry) to foods positioned between two electrodes for a brief duration. This process renders biological membranes permeable to small molecules, leading to swelling and eventual rupture of the cell membrane, thereby deactivating microorganisms. HPP uses water as a medium to exert significant pressure (usually ranging from 300 to 600 MPa in the food sector) on meals contained in flexible packets within a vessel.