Sviluppo di processi per la produzione di alimenti funzionali postbiotici

In the last few years, society is paying more attention to the quality of life and the concept of food is changing a lot. In this context, the notion of functional food has evolved. A functional food is defined as foods or food ingredients that exert a beneficial effect on host health and/or reduce the risk of chronic diseases beyond their basic nutritional functions. Lactic acid fermentation is one of the most important and used food processing technologies to produce probiotic functional foods. Moreover, recent evidences suggest that bacterial viability in a fermented product is not necessary to have a beneficial effect, but also soluble factors secreted by live bacteria or released after their lysis can contribute to the improvement of the host health, even if the exact mechanism is not well known yet; so in light of such evidence the concept of post-biotic has emerged intending a “post-biotic” as a kind of by-products of the fermentation process. This PhD project, in collaboration with Kraft Heinz company, aimed to develop a process for the production of postbiotic functional foods using a dairy and cereal substate. The process includes various phases: (i) the fermentation phase, (ii) a mild heat treatment phase for the inactivation of the bacterial charge in the fermented product obtaining a so called “post biotic food”, and (iii) a drying phase (freeze drying and spray drying technologies were studied to identify the best drying method and process conditions in order to avoid organoleptic and chemical food product alterations). The process was examined and optimized at lab scale and then implemented at pilot scale with a successful and efficient scaling up. The strain used for fermentation tests was Lactobacillus paracasei CBA L74, patented and provided by Kraft Heinz; tests were carried out on two different substrates: skimmed milk, and rice flour water suspensions. The products obtained at lab scale were characterised in terms of bacterial charge (a maximum growth of 1.9*108 ± 1.2*108 CFU/ml after 20h of fermentation and 5.3*108 ± 1.47*108 CFU/ml after 18h of fermentation was achieved for milk and rice flour fermentation, respectively) and lactic acid concentration (a maximum concentration of 1.2± 0.3 g/L and 4.4±0.21 g/L was achieved after 24h of fermentation for milk and rice flour fermentation, respectively), to follow the process’ performance and to identify its critical points; a thermal treatment of 90°C for 1 minute was sufficient to reduce the bacterial charge in the fermented product for both milk and rice without negatively affecting the products quality; freeze drying and spray drying technologies had the same impact on the food products, not altering their organoleptic and chemical properties: a promising result since spray drying technology is usually used at larger scale. Subsequently, the entire process was implemented at pilot scale and also in this case the products obtained from each process phases were characterised in terms of bacterial charge and lactic acid concentration in order to compare the results with those obtained at lab scale. All the results were completely overlapped, obtaining a maximum bacterial charge of 6.7*108 ± 2.65*108 CFU/ml after 20h of fermentation and 1.27*109 ± 6.9*108 CFU/ml after 18h of fermentation for milk and rice flour fermentation respectively ,and a maximum lactic acid concentration of 2.1±0.25 g/L and 6.03±0.7 g/L after 24h of fermentation for milk and rice flour respectively. A thermal treatment of 90°C for 1 minute was sufficient to reduce the bacterial charge in the fermented products and it was confirmed that spray drying technology had a low impact on the product. Moreover, a shelf life analysis of the products obtained at pilot scale was performed at three different storage temperature (4°C, 20°C and 37°C) for six months to evaluate the food product stability over time: dried fermented rice resulted more stable than milk. In parallel, another important goal of the project, which is currently subjected to confidentiality, was to develop a low-cost, fast and routinely analysis method to identify and dose the active compound present in the fermented product in order to characterised the products also from a functional point of view and understand how it changed during the various production phases; furthermore, finding a clear relationship between the bioactive element, the amount and the beneficial effect is a central concept that can provide a strong added value to the marketing of a functional food.