# What's in Your Fruit Juice?--Rapid Quality Screening Based on Infrared (FT-IR) Spectroscopy
###### Abstract  
Fruit juices (F) have gained widespread global consumption, driven by their perceived health benefits. The accuracy of nutrition information is essential for consumers assessing FJ quality, especially with increasing concerns about added sugars and obesity risk. Conversely, ascorbic acid (Vitamin C), found in nature in many fruits and vegetables, is often lost due to its susceptibility to light, air, and heat, and it undergoes fortification during FJ production. Current analytical methods for determining FJ components are time-consuming and labor-intensive, prompting the need for rapid analytical tools. This study employed a field-deployable portable FT-IR device, requiring no sample preparation, to simultaneously predict multiple quality traits in 68 FJ samples from US markets. Using partial least square regression (PLSR) models, a strong correlation (R\({}_{\text{CV}}\geq\) 0.93) between FT-IR predictions and reference values was obtained, with a low standard error of prediction. Remarkably, 21% and 37% of FJs deviated from nutrition label values for sugars and ascorbic acid, respectively. Portable FT-IR devices offer non-destructive, simultaneous, simple, and high-throughput approaches for chemical profiling and real-time prediction of sugars and acid levels in FJs. Their handiness and ruggedness can provide food processors with a valuable \"out-of-the-laboratory\" analytical tool. fruit juice; sugar content; ascorbic acid; FT-IR; portable sensor; real-time prediction; chemical profiling; obesity risk +
Footnote †: journal: _Applied_  
0000-0001-654X 0000  
demand, FJ manufacturers are focused on enriching the flavor and variety of FJs, also introducing novel packaging and product development. Thanks to the innovations in the juice industry, a variety of new juice blends have emerged, going beyond a single source of FJs. These blends serve both commercial purposes, introducing new product lines with distinct organoleptic features, and technological purposes, allowing the industry to take advantage of specific properties of certain juices, such as antioxidants [5]. In most cases, juices obtained from fruit(s) are not sold directly, and dilution with water and/or the addition of sugar or sweetener may involve reducing the sourness and/or for ideal consistency to facilitate juice consumption [1; 5]. In brief, the continuous innovations in the processing techniques of FJs and the blending of flavors have broadened the array of choices for consumers. In addition, ready-to-drink FJs provide convenience and portability, making them a popular choice for on-the-go consumption in busy lifestyles [4]. Ascorbic acid, also known as vitamin C, is naturally present in various fruits and vegetables and must be obtained from the diet to prevent scurvy, a clinical deficiency disease characterized by the deterioration of elastic tissues [6]. The recommended dietary allowance (RDA) for vitamin C is established at 60 mg. This recommendation is determined by considering the minimum amount of the vitamin excreted in the urine, aiming to ensure a safety margin against the development of scurvy [7]. Additionally, FJs are often supplemented with ascorbic acid for various purposes. This includes serving as an antioxidant to impede or slow down oxidation by suppressing oxidation promotors like transition metal ion catalysts, singlet oxygen, prooxidative enzymes, and other oxidants [8; 9]. The fortification of juices with vitamin C is a common practice to replace the ascorbic acid lost during processing and storage [10; 11; 12]. As a readily reactive reducing agent and a swiftly operating antioxidant, the levels of ascorbic acid can experience a significant and rapid decrease [9]. A study by [PERSON] and others revealed that, during refrigerated storage, the ascorbic acid content in blueberry juice depleted entirely within 7 days and dropped to half of the initial value within the initial 74 h. Similar trends were observed for pomeranate and cranberry juices, with a complete loss within 9 days of refrigerated storage.