Formulation and processing of a clean label apple based juice: The integration of high pressure based technologies and the use of natural ingredients

In recent years, food industry has shown a high interest in clean label foods, which are produced with more organic, natural, and transparent formulations and the use of less invasive processing technologies. Fresh or ‘not from concentrate fruit juices as natural and health-oriented beverages, have gained increasing market value around the world, particularly in developed countries. For these juices, browning, cloud losses, and flavor changes are the major quality defects particularly occurring during processing and subsequent storage. Fruit juice and beverage companies are searching for innovative solutions to overcome these quality problems. This work aimed at combining clean label approaches and high pressure processing (HPP, a preservation technology) to create fresh and natural cloudy fruit juice and to stabilize its quality characteristics during refrigerated storage. Since multi-response and complex (bio)chemical reactions and physical changes are responsible for quality deterioration, an integrated targeted and untargeted multivariate approach was developed and used as a central research strategy to identify and study quality changes during processing and storage. Cloudy apple juice, sensitive to quality defects such as browning, cloud losses and loss of authentic specific flavors, was selected as a case study. To achieve the objective, the experimental part was divided into two parts: (1) comparing HPP and conventional thermal processing (TP) on maintaining fresh-like quality characteristics of fruit based products (cloudy apple juice and kiwifruit puree); (2) evaluating the potential of a combination of a natural ingredient (kiwifruit puree) and a structure enabling technology (high pressure homogenization, HPH) to control quality losses of high pressure pasteurized cloudy apple juice during refrigerated storage. In Part I, to obtain a broad understanding on quality characteristics of apple juice and kiwifruit puree, three commercial apple cultivars (Pink lady, Granny smith, and Jonagold) and two kiwifruit cultivars (green kiwifruit, Actinidia deliciosa var.‘Hayward’; gold kiwifruit, Actinidia chinensis var.‘Jintao’) were studied in detail. Aiming for a fair comparison, HPP (600 MPa/3 min/21 °C) and TP ( ) conditions were selected based on the principle of equivalent microbial safety (5-log reduction of Escherichia coli O157:H7). This comparative study was performed by integrating both an untargeted headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) fingerprinting (to analyze the volatile fraction) and a targeted approach (to analyze a priori selected quality attributes such as color, sugars, acids, vitamin C, and enzymes). The results clearly demonstrated that HPP provided better retention of color and vitamin C compared to TP. However, polyphenol oxidase and peroxidase can be inactivated below detection limits by TP, while residual activity (> 50%) was detected after HPP. Regarding taste related compounds, sugars and acids were hardly affected by HPP and TP. Using the untargeted fingerprinting approach, aldehydes, alcohols, ketones, furanones, terpenes, and organosulfur compounds were detected with higher amounts after TP compared to untreated and HPP samples, which could be linked to the Maillard reaction and oxidative reactions. In general, the color and flavor of fruit based products seem to be more affected by TP compared to HPP, in particular the generation of thermally induced compounds responsible for cooked notes. Even though, the residual enzyme activities in the HPP juice could induce quality losses during subsequent storage, such as browning, cloud loss, and off-flavor. Therefore, there was a need to combine HPP with adapted pre-treatments (e.g. natural ingredients) to tackle these quality problems. Based on the results obtained of this part, gold kiwifruit puree showed a large potential as a natural ingredient that could be added to solve these problems. In Part II, HPH is considered as a physical pre-processing step, since it is an effective approach to improve the uniformity, reduce particle diameter, and modulate rheological characteristics. First, different levels of gold kiwifruit puree addition (0%, 10%, 25%, and 50%) and HPH conditions (No HPH, 20 MPa, 40 MPa, and 60 MPa) were studied. Next, the most successful options obtained (kiwifruit puree addition of 25% and HPH at 20 MPa) were combined with HPP (600 MPa/room temperature/3 min) to stabilize the quality of cloudy apple juice during 42 days refrigerated storage (4 °C). To verify this hypothesis, a wide range of quality parameters was evaluated using both targeted and untargeted approaches, including color, cloud stability, and flavor. Multivariate data analysis was conducted to select the discriminant and non-discriminant juice parameters, which clearly changed or did less change during storage, respectively. The detected discriminant quality parameters were further modelled by either single or multi-response kinetics to obtain their reaction rate constants during storage. Moreover, sensory evaluation and visual assessment were included. Results showed that the use of gold kiwifruit puree addition and HPH resulted in a juice with improved uniformity and cloud stability by reducing particle size and increasing viscosity, and yield stress. Besides, gold kiwifruit puree addition reduced enzymatic browning of HPP cloudy apple juice due to the increased ascorbic acid content and contributed to a more saturated and bright yellow juice color, and a less sweet, and a more fruity juice aroma. Based on visual and sensory evaluations, better color, aroma, and cloud stability were observed for apple juice supplemented with gold kiwifruit puree. In conclusion, combining clean label approaches consisting of gold kiwifruit puree addition and HPH followed by high pressure preservation processing technology is an effective approach to produce a natural and refrigerated shelf-life stable cloudy (apple) juice. On the other hand, this work also confirmed the potential of a combination of targeted and untargeted multivariate approaches followed by kinetics to identify and to study complex food quality changes.status: publishe