Periodic Reporting for period 1 - HiStabJuice (Establishing a strong and lasting international training network for innovation in food and juice industries: a 4D-research approach for fruit juice processing)
Berichtszeitraum: 2020-11-01 bis 2022-10-31
HiStabJuice is a European intersectoral and interdisciplinary network offering research training to 11 ESRs, which is relevant to the entire food industry worldwide. Initiated by the International Fruit and Vegetable Juice Association (IFU), the ETN combines the scientific expertise of 5 universities and 2 research institutions with the technological experience of 10 industry partners from 7 EU countries. This ETN stands out by its exceptionally high industrial involvement that ensures training in real-world abilities and in solving key problems with exceptional analytical and technological skills, combined with training in key transferable skills for public and private sector employment. The ESRs will work together on the evaluation of various factors influencing colour stability in fruit juices, focussing on raw materials and preservation techniques, as well as associated effects, deleterious to the health benefits of the final products. Pioneering aspects include the first empirical analysis of the contribution to colour stability and nutritional value of thermostable enzymes, fruit variety, ripeness, harvest time, traditional and modern preserving techniques (pasteurization, freezing, pulsed electric field, ohmic heating, high-pressure processing), which will be evaluated in a 4D approach (microbes, enzymes, nutrients and chemical-physical parameters). Upon conclusion of the action, the ESRs will have established a universal, empirical system for deciding which fruit types to harvest at which times, at which stage of the ripening process, and which preservation method will give the best colour and nutrient stability. In line with the Horizon2020 strategic priority of Open Science, this knowledge will be freely accessible. This has the potential to revolutionise the fruit juice industry and will fortify the European industry for decades to come. The participation of IFU guarantees unsurpassed intercommunication between the ETN and industry stakeholders across the EU.
So far 11 endogenous enzymes presumably involved in browning reactions have been identified and heterologously expressed in E.coli or yeast with characterization ongoing. The inactivation of selected enzymes using non-thermal treatments and HPP has already been achieved. Inactivation kinetics of two EHEC strains and 5 Salmonella strains, in vitro in different matrixes, was determined. Selected bacterial surrogate strains with known inactivation kinetics have been provided for evaluation at industrial conditions. The effect of raw material on the colour stability of strawberry nectars was assessed considering more than 100 cultivars, thereof 14 cultivars collected at different ripeness stages and harvest points and a colour stability prediction model was successfully established. The 14 cultivars were also characterized regarding their polyphenol content, selected primary metabolites (sugar, ascorbic acid) and cell wall. The effect of different defrosting regimes, freezing regimes and post-harvest storage on colour stability was examined. Strawberry preparations from a commercial supplier were made available to all involved ESRs to ensure interactive and common work on comparable plant material. Methods for determination and quantification of enzymatic activity for polyphenol oxidases (PPO) and peroxidases (POD) in strawberry nectars were established. Multivitamin analysis methods using HPLC-MS/MS were developed for the water-soluble vitamins (B vitamins and Vitamin C) and validated in strawberry nectar and multivitamin juice according to ISO/DTS 21748. Initial trials compared conventional thermal pasteurization (TT) and HPP in terms of the main physicochemical parameters i.e. colour, apparent viscosity, total soluble solid content, and pH. Microbiological analyses were performed to study the influence and differences of the different treatments on microbial load.
Highlights of the previous research are the identification of eleven sequences of enzymes presumably involved in browning reactions in strawberry fruits and nectar (ESR1), which are currently under investigation (ESRs 2, 3) and the characterization of two surrogate strains (ESR9) for evaluation of four conservation methods in industrial environments. Screening of more than 100 strawberry varieties for colour stability during processing identified two promising candidates of potential commercial interest and resulted in a colour prediction model (ESR5). Correlation of the ripening stage with colour and stability i.e. fruits with better organoleptic characteristics and higher concentrations of anthocyanins, was established (ESRs 4, 11). Multivitamin analysis methods using HPLC-MS/MS were developed for the water-soluble B and C vitamins (ESR10). A time-temperature chart for the reductions of microorganisms, enzymes, nutrients, and physical-chemical properties for strawberry nectar is currently being finalized (ESRs 6-11) and will be further elaborated for sour cherry and red grape juice. Resuming in only one graph information about microbial isolog- reductions, iso-percentage-inactivation of different enzymes, iso-percentage-loss of nutrients and chemical – physical parameters variations will represent a crucial breakthrough in the optimization and customization of the fruit treatments and will be made generally available to the fruit processing industry as supporting documentation for processors. This will prove to be of tremendous relevance in Europe, given the enormous economic relevance of the fruit juice industry and the growing popularity among consumers of direct fruit juice, particularly on the European market. A standardised system for choosing the appropriate conventional or non-conventional processing method(s) prior to shipping will is something that has been sorely lacking in the industry for a very long time.