Survival of Lactobacillus salivarius CECT 4063 and Stability of Antioxidant Compounds in Dried Apple Snacks as Affected by the Water Activity, the Addition of Trehalose and High Pressure Homogenization

Development of an Apple Snack Enriched with Probiotic Lacticaseibacillus rhamnosus: Evaluation of the Refractance Window Drying Process on Cell Viability

The objective of this study was to develop a dried apple snack enriched with probiotics, evaluate its viability using Refractance Window (RWTM) drying, and compare it with conventional hot air drying (CD) and freeze-drying (FD). Apple slices were impregnated with Lacticaseibacillus rhamnosus and dried at 45 °C using RWTM and CD and FD. Total polyphenol content (TPC), color (∆E*), texture, and viable cell count were measured, and samples were stored for 28 days at 4 °C. Vacuum impregnation allowed for a probiotic inoculation of 8.53 log CFU/gdb. Retention values of 6.30, 6.67, and 7.20 log CFU/gdb were observed for CD, RWTM, and FD, respectively; the population in CD, RWTM remained while FD showed a decrease of one order of magnitude during storage. Comparing RWTM with FD, ∆E* was not significantly different (p < 0.05) and RWTM presented lower hardness values and higher crispness than FD, but the RWTM-dried apple slices had the highest TPC retention (41.3%). Microstructural analysis showed that RWTM produced a smoother surface, facilitating uniform moisture diffusion and lower mass transfer resistance. The effective moisture diffusion coefficient was higher in RWTM than in CD, resulting in shorter drying times. As a consequence, RWTM produced dried apple snacks enriched with probiotics, with color and TPC retention comparable to FD.

Dynamics of Active Fluorescent Units (AFU) and Water Activity (aw) Changes in Probiotic Products-Pilot Study

The flow cytometry method (FCM) is a widely renowned practice increasingly used to assess the microbial viability of probiotic products. Additionally, the measurement of water activity (aw) can be used to confirm the presence of viable cells in probiotic products throughout their shelf lives. The aim of this study was to investigate the correlation between changes in aw and variations in active fluorescent units (AFU), a unit commonly used in flow cytometry method, during the aging of probiotic products containing freeze-dried bacteria. We controlled the stability of probiotic products for bacterial counts (using ISO 19344 method) and aw levels in commercially available capsules containing freeze-dried bacteria such as Lactobacillus sp. or combinations of Lactobacillus sp. and Bifidobacterium sp. in standard conditions (25 ± 2 °C and 60% relative humidity) over a period of 24 months. During this time, the bacterial contents decreased by 0.12 Log10 in the single-strain product, by 0.16 Log10 in the two-strain product and by 0.26 Log10 in the multi-strain product. With the increase in aw, the number of bacteria decreased but the aw at the end point of the stability study did not exceed 0.15 in each of the three tested products. FCM combined with aw is a prospective analysis that can be used to assess the stability of probiotic products, both for its ability to detect bacterial viability and for practical (analysis time) and economic reasons.

Development of a Technology for Protein-Based, Glueless Belevskaya Pastille with Study of the Impact of Probiotic Sourdough Dosage and Technological Parameters on Its Rheological Properties

The proper functioning of the gastrointestinal tract plays an important role in strengthening the immune system. It is an undeniable fact that lactic acid microorganisms are necessary for the proper functioning of the gastrointestinal tract, the source of which are mainly dairy products. However, there is a problem with the digestibility of lactose; therefore, alternative sources and carriers of probiotics are of particular interest. Due to its dietary and natural properties, protein marshmallow can serve as such a carrier. Therefore, the direction of this study is to identify the dependence of technological factors on the rheological properties of the product and the growth of lactic acid microorganisms in confectionery products enriched with lyophilised strains. According to the results of the study, the following was determined: the optimal technology to produce enriched Belevskaya pastille with a mixture of Lactobacillus acidophilus makes it possible to obtain a product with the necessary rheological properties, utilising a mass drying mode in a dehydrator at 50 °C for 16 h. The strains L. acidophilus M3 and L. acidophilus M4 were the most resistant to a high concentration of bile (40%) in the substrate. Based on the analysis of variance and the obtained regression equations, it was revealed that the growth of lactic acid microorganisms in the product was strongly influenced by the amount of ferment introduced (R² = 0.96). The level of penetration is influenced by factors such as the amount of probiotic starter introduced, the drying time and the interaction of drying time factors on the amount of starter added. The higher the level of penetration, the crumblier the product. The resulting functional product can be characterized as symbiotic since the main raw material of plant origin contains a large amount of fibre, which acts as a prebiotic, and the strain of microorganism, which acts as a probiotic. The data described in the article can be applied in the technological processes of similar products to regulate the structure of the product and vary the dosage of enrichment with probiotic starter cultures.

Influence of Temperature during Freeze-Drying Process on the Viability of Bifidobacterium longum BB68S

Maintaining optimum temperature during freeze-drying is crucial to ensuring the viability of strains. In this study, we evaluated the effect of pre-freezing, sublimation and desorption temperatures on the viability of Bifidobacterium longum BB68S (BB68S). Moreover, we examined the water content, water activity, enzyme activities, and scanning electron microscope of BB68S to explore mechanisms underpinning the effect of temperature on viability. Our analyses revealed the highest survival rates of BB68S collected after pre-freezing and sublimation drying at -40 °C (94.9 ± 2.2%) and -10 °C (65.4 ± 3.8%), respectively. Additionally, response surface methodology demonstrated that the optimum conditions for freeze-drying of BB68S were pre-freezing temperature at -45.52 °C and sublimation temperature at -6.58 °C, and the verification test showed that survival rates of BB68S could reach 69.2 ± 3.8%. Most of the vitality loss occurred during the sublimation drying phase. Further studies showed that different sublimation temperatures affected water content and activity, β-galactosidase, lactate dehydrogenase, Na+-K+-ATP and Ca2+-Mg2+-ATP activities. In conclusion, the temperature during freeze-drying, especially sublimation temperature, is a key factor affecting the survival rate of BB68S, and the vitality loss during freeze-drying process might be due to compromised cell membrane integrity and permeability.

Influence of Temperature during Freeze-Drying Process on the Viability of Bifidobacterium longum BB68S

Maintaining optimum temperature during freeze-drying is crucial to ensuring the viability of strains. In this study, we evaluated the effect of pre-freezing, sublimation and desorption temperatures on the viability of Bifidobacterium longum BB68S (BB68S). Moreover, we examined the water content, water activity, enzyme activities, and scanning electron microscope of BB68S to explore mechanisms underpinning the effect of temperature on viability. Our analyses revealed the highest survival rates of BB68S collected after pre-freezing and sublimation drying at -40 °C (94.9 ± 2.2%) and -10 °C (65.4 ± 3.8%), respectively. Additionally, response surface methodology demonstrated that the optimum conditions for freeze-drying of BB68S were pre-freezing temperature at -45.52 °C and sublimation temperature at -6.58 °C, and the verification test showed that survival rates of BB68S could reach 69.2 ± 3.8%. Most of the vitality loss occurred during the sublimation drying phase. Further studies showed that different sublimation temperatures affected water content and activity, β-galactosidase, lactate dehydrogenase, Na⁺-K⁺-ATP and Ca²⁺-Mg²⁺-ATP activities. In conclusion, the temperature during freeze-drying, especially sublimation temperature, is a key factor affecting the survival rate of BB68S, and the vitality loss during freeze-drying process might be due to compromised cell membrane integrity and permeability.

Fermentation of Clementine Juice with Lactobacillus salivarius spp. salivarius CECT 4063: Effect of Trehalose Addition and High-Pressure Homogenization on Antioxidant Properties, Mucin Adhesion, and Shelf Life

Fermentation of fruit juices with lactic acid bacteria enhances their antioxidant properties to a different extent depending on the microbial strain and the growing media composition, which can be modified by adding certain ingredients or applying a homogenization step. This study analyzed the effect of trehalose addition (10%, w/w) and homogenization at 100 MPa before or after Lactobacillus salivarius spp. salivarius CECT 4063 inoculation on the antioxidant profile and the microbiological properties of commercial clementine juice during 96 h fermentation. Antioxidant properties and viable cell count of 24 h-fermented juices during refrigerated storage (30 days at 4 °C) were also evaluated. Fermentation over 24 h reduced the microbial population and antioxidant content of clementine juice. Homogenizing the juice before inoculation enhanced the microbial growth but favored antioxidant degradation. Adding trehalose (10%, w/w) to the juice formulation and/or homogenizing at the fermented juice at 100 MPa for 24 h had a negative impact on viable counts and did not improve the microbial adhesion to intestinal mucosa. However, both techniques prevented antioxidant oxidation and cell decay during the storage of fermented juice under refrigeration, which should not last more than 15 days.

Ligilactobacillus salivarius functionalities, applications, and manufacturing challenges

Ligilactobacillus salivarius is a lactic acid bacteria that has been gaining attention as a promising probiotic. Numerous strains exhibit functional properties with health benefits such as antimicrobial activity, immunological effects, and the ability to modulate the intestinal microbiota. However, just a small number of them are manufactured at an industrial scale and included in commercial products. The under exploitation of L. salivarius strains that remain in the freezer of companies is due to their incapacity to overcome the environmental stresses induced by production and stabilization processes.The present study summarizes the functionalities and applications of L. salivarius reported to date. It aims also at providing a critical evaluation of the literature available on the manufacturing steps of L. salivarius concentrates, the bacterial quality after each step of the process, and the putative degradation and preservation mechanisms. Here, we highlight the principal issues and future research challenges for improving the production and long-term preservation at the industrial scale of this microorganism, and probably of other probiotics.Key points• L. salivarius beneficial properties and commercialized products.• Production conditions and viability of L. salivarius after stabilization processes.• Prospects for identifying preservation mechanisms to improve L. salivarius stability.

Antioxidants Bioaccessibility and Lactobacillus salivarius (CECT 4063) Survival Following the In Vitro Digestion of Vacuum Impregnated Apple Slices: Effect of the Drying Technique, the Addition of Trehalose, and High-Pressure Homogenization

To benefit the health of consumers, bioactive compounds must reach an adequate concentration at the end of the digestive process. This involves both an effective release from the food matrix where they are contained and a high resistance to exposure to gastrointestinal conditions. Accordingly, this study evaluates the impact of trehalose addition (10% w/w) and homogenization (100 MPa), together with the structural changes induced in vacuum impregnated apple slices (VI) by air-drying (AD) and freeze-drying (FD), on Lactobacillus salivarius spp. salivarius (CECT 4063) survival and the bioaccessibility of antioxidants during in vitro digestion. Vacuum impregnated apple slices conferred maximum protection to the lactobacillus strain during its passage through the gastrointestinal tract, whereas drying with air reduced the final content of the living cells to values below 10 cfu/g. The bioaccessibility of antioxidants also reached the highest values in the VI samples, in which the release of both the total phenols and total flavonoids to the liquid phase increased with in vitro digestion. The addition of trehalose and homogenization at 100 MPa increased the total bioaccessibility of antioxidants in FD and AD apples and the total bioaccessibility of flavonoids in the VI samples. Homogenizing at 100 MPa also increased the survival of L. salivarius during in vitro digestion in FD samples.

Impact of Sugar Type Addition and Fermentation Temperature on Pomegranate Alcoholic Beverage Production and Characteristics

The present study focuses on the production of pomegranate alcoholic beverage (PAB) from juice of the Wonderful variety. The effect of fermentation temperature (15 and 25 °C) and type of sugar added (adjustment to 20 °Brix) on the physicochemical characteristics, bioactive compounds, and volatile composition were studied. Sucrose, concentrated pomegranate juice, concentrated grape juice, and honey were used to increase the initial sugar content. The produced PABs contained ethanol in concentrations ranging from 7.9 to 10.0% v/v and glycerol from 4.8 to 6.1 g L⁻¹. A decrease in total phenolics content, free radical-scavenging activity, and total monomeric anthocyanin content was observed following fermentation. Total flavonoids content appeared to increase after fermentation only in the cases of concentrated pomegranate and grape juice addition. In general, 22 volatile compounds were identified in PABs (13 esters, 2 fatty acids, and 7 alcohols). Major compounds detected were 3-methyl-1-butanol, 2-methyl-1-butanol, 2-phenylethanol, and ethyl acetate. These findings demonstrate the production prospect of PABs with increased ethanol content, while elaborating on the importance of fermentation temperature and the differences between the selected types of added sugars on end-product composition.

Editorial for Special Issue "Lactic Acid Bacteria, Biopreservation Agents for Fruit and Vegetables"

Amongst the microbial diversity in the food chain, lactic acid bacteria (LAB) are in the front row for their positive roles [...].