Abstract
Fruit and vegetables are considered good natural supports for microorganisms; however, probiotics could cause negative changes on some organoleptic and sensory traits. Thus, the main topic of this paper was the design of coated apple chips as carriers for probiotics with a high level of sensory traits. The research was divided into two steps. First, four functional strains (Limosilactobacillus reuteri DSM 20016, Bifidobacterium animalis subsp. lactis DSM 10140, and Lactiplantibacillus plantarum c16 and c19) were immobilized on apple pieces through dipping of fruit chips in probiotic suspensions for different contact times (from 15 to 30 min) and stored at 4°C for 12 days. Periodically, the viable count was assessed. As a result of this step, a contact time of 15 min was chosen because it assured an optimal deposition of microorganisms. In the second step, apple pieces inoculated with B. animalis subsp. lactis DSM 10140 were coated with alginate and gelatin and stored at 4 and 8°C for 10 days; pH, microbiological counts, color (browning index), and sensory scores were evaluated. Bifidobacterium animalis DSM 10140 exerted a negative effect on apple chips and cause a significant browning; however, the use of coating counteracted this phenomenon. In fact, coated chips showed higher sensory scores and lower browning index. In addition, gelatin showed better performances in terms of probiotic viability, because at 8°C, a significant viability loss of B. animalis DSM 10140 (1.2 log cfu/g) was found on alginate-coated chips. Gelatin-coated apple pieces with B. animalis subsp. lactis DSM 10140 could be an attractive functional food for a wide audience, although further investigations are required on in vivo effects of this product after consumption.
Highlights
Cell immobilization is the physical confinement of intact cells to a well-defined region of space; a requisite of immobilization is that cells retain their biological activity (Karel et al, 1985)
The viability of B. animalis subsp. lactis 10140 on apple pieces coated with sodium alginate and gelatin and stored at 4 and 8◦C for 10 days was evaluated
A dipping time of at least 15 min was used; the results showed that the level of probiotics on apple pieces was not influenced by the contact time; for the easiness of the process, a contact time of 15 min was regarded as acceptable for the second step of this research
Summary
Cell immobilization is the physical confinement of intact cells to a well-defined region of space; a requisite of immobilization is that cells retain their biological activity (Karel et al, 1985) This technology was successfully applied on food-grade microorganisms for technological purposes; for example, Moreno-García et al (2018) reported that it is possible to confine intact and active yeasts to a specific region, increasing cell density, enhancing some metabolic pathways, improving the. Fruits are composed of non-digestible carbohydrates, which are the base for cell immobilization; due to their cellulose content, some fruits, such as apples and pears, may exert a protective effect on the probiotic microorganisms during passage through the intestinal tract allowing these microorganisms (such as Lacticaseibacillus casei) to reach the colon and benefit the host (Kourkoutas et al, 2006). Apple and quince pieces proved to be appropriate carriers for immobilization of L. casei cells (Kourkoutas et al, 2006), Lactiplantibacillus plantarum (Speranza et al, 2018), and Saccharomyces cerevisiae (Altieri et al, 2019)
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