Mixed fermentation of jujube juice (Ziziphus jujuba Mill.) with L. rhamnosus GG and L. plantarum-1: effects on the quality and stability

This study was conducted aiming at improving the quality of jujube juice by mixed fermentation of lactobacilli. Selection of favourable lactobacilli and addition of nitrogen sources were explored as an efficient method to improve the viability of probiotic in jujube juice. After fermentation, the viability increased to 9.15 ± 0.10 Log CFU mL⁻¹, while the content of lactic acid increased to 5.61 ± 0.03 mg mL⁻¹. The total phenolic and total flavonoid content were 2663.03 ± 11.95 μg mL⁻¹ and 163.95 ± 0.47 μg mL⁻¹ respectively. Moreover, the stability of fermented jujube juice during refrigeration was investigated, which showed that the viability dropped to 8.84 ± 0.6 Log CFU mL⁻¹ and the concentration of lactic acid slowly increased to 6.51 ± 0.04 mg mL⁻¹; the ABTS value showed a 4.26% reduction and FRAP value did not significantly (P < 0.05) change during refrigerated storage. In addition to the existing knowledge, our data aid to the future applications of the jujube as a potential ingredient in novel probiotic foods formulation.     

Reduction of Listeria monocytogenes in cold‐smoked salmon by bacteriophage P100, nisin and lauric arginate,singly or in combinations

Three GRAS antimicrobials including, lauric arginate (LAE), bacteriophage P100 (phage P100) and bacteriocin nisin, were evaluated either singly or in combinations for the reduction of initial load of Listeria monocytogenes in cold‐smoked salmon (CSS). The stability of phage P100 in the presence of LAE (200 ppm) and nisin (500 ppm) or at 10× and 100× of these concentrations was determined at 4 °C or 30 °C for 24 h in a broth model. Phage P100 was found to be highly stable in the presence of these antimicrobial agents as plaque‐forming units (PFU) did not vary between control and antimicrobial‐treated phage. The survival of L. monocytogenes in the presence of phage P100, nisin and LAE showed remarkable reduction within 24 h both at 4 °C or 30 °C in broth. Treatment of CSS containing 3.5 log CFU cm^?2 L. monocytogenes with phage P100 (10⁸ PFU mL^?1), nisin (500 ppm) and LAE (200 ppm) showed strong listericidal action and reduced the L. monocytogenes by 2–3 log CFU cm^?2 after 24 h. Among the combined treatments, phage P100 + LAE or nisin + LAE exhibited the most listericidal action in which L. monocytogenes cells were reduced to undetectable level within 24 h in CSS.     

Co‐inoculation of yeast and lactic acid bacteria to improve cherry wines sensory quality

This study examined the effect of co‐inoculation of yeast and lactic acid bacteria (LAB) on the chemical and sensory characteristics of cherry wines, in comparison with a traditional sequential culture. Three LABs were investigated, including two O. oeni (SG26 and Viniflora) and one L. plantarum (PL18). All co‐inoculations significantly shortened the fermentation time (average 8 days earlier) to reach a stable level of residual sugar (<2 g L^?1) and L‐malic acid (<0.5 g L^?1), and no inhibitory effect on the yeast proliferation was observed. For volatiles determined, co‐culture with SG26 produced the greatest amount of volatile components (138.5 mg L^?1), whereas sequential inoculation with PL18 had the lowest level (119.6 mg L^?1). PCA result revealed that different LABs had diverse influences on the volatile profile of cherry wines, and sensory analysis confirmed that these samples presented distinct sensory profiles, and particularly, a stronger note of fruity was perceived when co‐culture was used.     

Antimicrobial activities of high molecular weight water‐soluble chitosans against selected gram‐negative and gram‐positive foodborne pathogens

Antimicrobial activities of high molecular weight water‐soluble chitosans (HMWWS) against selected Gram‐negative and Gram‐positive foodborne pathogens (initial inoculation of ca. 6.5 Log CFU mL^?1) were evaluated. Chitosans with 789 kDa and/or 1017 kDa were dissolved in aspartic acid (AS) to obtain 1–4% w/v solutions. Among HMWWS, only 4% 789 kDa AS chitosan reduced E. coli counts by 2 Log CFU mL^?1 from 7.33 at 0 h to 5.16 Log CFU mL^?1 at 96 h, and they were not effective against S. Typhimurium. Depending on the concentrations, HMWWS completely inhibited V. cholerae, V. vulnificus and V. parahaemolyticus as well as B. cereus and L. monocytogenes after 48 h or 96 h of incubation. Compared with the control (no HMWWS), 2% or 3% 1017 kDa AS chitosans showed about 3 Log CFU mL^?1 lower (4.72–4.86 vs. 7.71) for S. aureus at 96 h of incubation.     

Malolactic fermentation in sea buckthorn (Hippophaë rhamnoides L.) juice processing

Malolactic fermentation (MLF) traditionally used in winemaking was applied to sea buckthorn to reduce the high sourness of the berry juice. Chemical and microbiological aspects, as well as sensory properties of the juice during MLF were studied in order to develop an optimal process. In 1:1 water diluted juice with malic acid content of 15 g/l and pH 2.8, efficient conversion of l-malic acid to l-lactic acid was achieved with direct inoculation of unadapted Oenococcus oeni at a cell density of 10⁹ CFU/ml. The rapid malic acid degradation was performed by non-growing bacterial cells without loss of sugars, vitamin C, or pulp oil. More than 50% of the initial malic acid was metabolized to lactic acid and CO₂ already in 12 h of fermentation and a significant decrease in sourness and astringency was noticed. In 24 h fermentation, pH value was increased to 3.1 and only 3 g/l malic acid remained in the juice. Prolonged fermentation had only minor effect on malolactic reaction, but off-flavor of the juice began to increase.     

Encapsulation of probiotic Lactobacillus acidophilus by ionic gelation with electrostatic extrusion for enhancement of survival under simulated gastric conditions and during refrigerated storage

The probiotic Lactobacillus acidophilus was encapsulated in biodegradable and biocompatible capsules prepared by ionic gelation between phytic acid (PA) and chitosan (CS) with an electrostatic extrusion method. Calcium carbonate (CaCO₃) and starch were used as co‐encapsulants for improvement of capsule stability. Capsules were characterised and evaluated for survival of encapsulated L. acidophilus cells in simulated gastric fluid (SGF) and during refrigerated storage. Loading capacity values of PA‐CS capsules, PA‐CS‐starch capsules and PA‐CS‐CaCO₃ capsules were 8.20, 8.12 and 7.81 log CFU g^?1 of wet capsule, respectively. Capsules showed particle sizes of 1.3–1.5 mm and a uniform spherical shape. PA‐CS‐CaCO₃ capsules were the most stable vehicles for the protection of probiotic cells against acidic damage, particularly at pH 1.5 and pH 2. L. acidophilus cells from PA‐CS‐CaCO₃ capsules showed only a 0.64 log CFU reduction in numbers after 2 h in pH 1.5 SGF conditions. The numbers of L. acidophilus encapsulated in PA‐CS‐CaCO₃ capsules were decreased by only 0.69 log CFU g^?1, while PA‐CS capsules and PA‐CS‐starch capsule numbers were reduced by more than 1.45 log CFU g^?1 after 4 weeks at 4 °C. Addition of calcium carbonate to PA‐CS capsules provided protection against acid injury via antacid and buffering effects for encapsulation of L. acidophilus.     

Isolation,characterisation and fermentation optimisation of glucansucrase‐producing Leuconostoc mesenteroides DRP105 from sauerkraut with improved preservation stability

A total of fifty‐six strains of lactic acid bacteria isolated from Chinese sauerkraut juice from Shenyang were screened for glucansucrase production. Among them, strain DRP105 was detected to produce highest yield of glucansucrase in MRS broth, which was identified to be Leuconostoc mesenteroides. Based on Plackett–Burman Experiment, sucrose, sodium acetate and initial pH were found to be the most significant factors for glucansucrase production of L. mesenteroidesDRP105. Afterwards, effects of the three main factors on glucansucrase activity were further investigated by central composite design, and the optimum composition was sucrose 35.74 g L^?1, sodium acetate 6.46 g L^?1 and initial pH 5.90. Optimum results showed that glucansucrase activity was increased to 6.26 ± 0.09 U mL^?1 in 24 h fermentation, 33.19% higher than before. Our study also suggested that Tween 80 and dextran have potential to improve glucansucrase stability at temperature (30 °C) higher than enzyme storage temperature in crude fermented broth.     

Cashew Apple Juice as Substrate for Lactic Acid Production

The aim of the present work was to investigate the use of cashew apple juice as a low cost substrate for Lactobacillus casei B-442 cultivation and lactic acid production. Ammonium sulfate was employed as the only exogenous nitrogen source. The effect of cashew apple juice reducing sugars and ammonium sulfate concentration and the fermentation pH and temperature on biomass formation, lactic acid production, and productivity were evaluated. The highest productivity (2.36 g/L.h) was obtained applying 50 g/L of reducing sugar from the cashew apple juice supplemented with 6 g/L of ammonium sulfate. The process yield was about 95% when fermentation was carried out at 37 °C with pH controlled at pH 6.5 using NaOH (120 g/L).     

Effects of Pseudomonas chlororaphis and gaseous chlorine dioxide on the survival of Salmonella enterica on tomatoes

Control of Salmonella enterica on tomatoes is important for food safety. The aim of this research was to evaluate the survival of Salmonella enterica serovars Montevideo (SM) and Typhimurium (ST) on tomatoes exposed to gaseous chlorine dioxide and Pseudomonas chlororaphis (Pc). Pc was applied to stem scars of tomatoes prior to inoculations with SM and ST. Tomatoes were treated with gaseous ClO₂ at 0.4 mg L^?1 for 2 and 4 h (90% R.H. 13 °C), respectively. At 4 h of ClO₂ treatment, SM and ST populations were reduced to 0.82 and <0.30 log CFU g^?1, respectively. Tomatoes treated with SM and ST had 5.42 and 5.37 log CFU g^?1 of Salmonella. Tomatoes treated with Pc + Salmonella count was 2.59 (treated) and 5.83 log CFU g^?1 (control). Salmonella survival was similar at 2 and 4 h of ClO₂ treatment. Application of ClO₂ and Pc may reduce contamination of tomatoes by Salmonella serovars.     

Preparation and optimization of soy protein isolate–high methoxy pectin microcapsules loaded with Lactobacillus delbrueckii

This study was aimed to use soy protein isolate (SPI) and high methoxy pectin (HMP) as encapsulating materials for probiotic bacterial (Lactobacillus delbrueckii) delivery systems. The encapsulation conditions were optimised, and scanning electron microscopy (SEM) was used to characterise the microstructural changes of the microcapsule. The results showed that the optimal conditions for microcapsule preparation were 90 mg mL^?1 SPI and 1 mg mL^?1 HMP, with a SPI/HMP ratio of 7:1 (v/v), and a L. delbrueckii suspension to SPI–HMP complex ratio of 1:1 (v/v). The viability of the probiotics in the microcapsules reaching the small intestine was 3 log CFU mL^?1 higher than that of naked bacteria. SEM showed that the surface of the SPI–HMP compound microcapsules was smooth and that a large number of L. delbrueckii could be seen in cross‐sections of the microcapsules.     

Effect of gums on viability and β‐galactosidase activity of Lactobacillus spp. in milk drink during refrigerated storage

The viability and β‐galactosidase activity of four Lactobacillus strains in milk drink containing gums during 28 days of refrigerated storage at 4 °C were assessed. The population of Lactobacillus rhamnosus GGB101 and Lactobacillus rhamnosus GGB103 were maintained, whereas the population of Lactobacillus reuteri DSM20016 and Lactobacillus reuteri SD2112 significantly decreased. The recommended level of 6 log CFU g^?1 was exceeded for all tested trains throughout storage. The highest viable number of Lactobacillus rhamnosus GGB103 (8.76 ± 0.03 log CFU mL^?1) was obtained in the product containing carrageenan–maltodextrin. The addition of guar–locust bean–carrageenan led to 20‐fold increase in the level of β‐galactosidase activity for L. rhamnosus GGB101 (1208 ± 2.12 Miller units mL^?1) compared to the control (61 ± 2.83 Miller units mL^?1). Our results suggested that gums could be added to milk to improve viability and enhance β‐galactosidase activity of Lactobacillus.     

Effect of different levels of fat and inulin on the microbial growth and metabolites in probiotic yogurt containing nonviable bacteria

Effects of different levels of fat and inulin on bacterial cell counts, degree of proteolysis and concentrations of organic acids in the yogurt containing inactivated cells of probiotic strains Bifidobacterium animalis and Lactobacillus acidophilus were investigated. Results showed that both L. acidophilus and B. animalis grew well in the yogurt samples reaching cell counts higher than 10⁶ CFU mL^?1 at the final pH of 4.5. Inulin at the concentration of 1% had no significant effects on the production of organic acids and cell counts of L. acidophilus, but promoted the growth of B. animalis with a reduction in the degree of proteolysis. Generally, different fat levels showed significant effects on the production of organic acids and nonsignificant effects on the cell counts of probiotic bacteria and degree of proteolysis. In case of lactic acid, the ratio of L‐ (+)to D‐ (?) isomer ranged from 50/50 to 80/20 in yogurt samples.     

Tannase improves gallic acid bioaccessibility and maintains the quality of mango juice

The effect of tannase on gallic acid (GA) bioaccessibility and auto-oxidative browning of mango juice was investigated. After 2 h of simulated gastric digestion, the concentration of bioaccessible GA increased (P < 0.05) 94.3 ± 7.0% in juice treated with 0.5 U mL⁻¹ tannase while juice not treated with tannase had only a 6.3 ± 3.4% increase in GA. During 2–10 h of simulated intestinal digestion, tannase treated juice continued to have a higher concentration (P < 0.05) of bioaccessible GA in comparison to juice that was not treated with tannase. The use of 167 U 100 mL⁻¹ tannase while processing mango juice did not result in any differences (P < 0.05) in browning measured at 420 nm, yet there was significantly higher (P < 0.05) GA in mango juice post-storage. Processing mango juice with tannase can help improve the bioaccessibility of mango polyphenols without hindering the quality of juice during storage.     

Anti‐inflammatory and cytotoxic effects of ginseng extract bioconverted by Leuconostoc mesenteroides KCCM 12010P isolated from kimchi

A bioconversion technique using microorganisms has been applied to ginseng to increase content of bioactive ginsenoside and biofunctionality such as anticancer, anti‐obesity and antioxidant activities. The objective of this study was to screen lactic acid bacteria for bioconversion of ginsenosides and to evaluate anti‐inflammatory and cytotoxic effects of bioconverted ginseng extract. Strains isolated from kimchi were screened for their β‐glucosidase activities using esculin agar. Selected strain was identified based on 16S rRNA sequencing and carbohydrate fermentation. During ginseng fermentation, viable cell number and pH were determined. Bioconverted ginsenosides were analysed by HPLC. Anti‐inflammatory effects were evaluated using RAW 264.7 cells, and cytotoxic effects were determined by MTT assay. Among 166 isolates screened, Leuconostoc mesenteroides was selected for ginseng bioconversion, as it showed a higher β‐glucosidase activity and viable cell number than any of the other tested strains. After fermentation for 2 days, viable cell number was 8.8 log CFU mL^?1 and final pH was 4.8. Ginsenoside Rb₂ was bioconverted into ginsenoside Rg₃ (Rb₂ → Rd → Rg₃) by L. mesenteroides. The nitric oxide contents of 2‐day‐fermented extract decreased by as much as 25%, compared to a non‐fermented extract. The cell viabilities of HepG2, HT‐29, HeLa and LoVo treated with fermented ginseng extract also decreased by 49.7%, 20.2%, 21.0% and 8.7%, respectively, compared to those of control cells treated with non‐fermented extract. Ginseng extract bioconverted by L. mesenteroides showed anti‐inflammatory and anticancer effects. Therefore, bioconverted ginseng extract might have applications in the pharmaceutical and/or functional food industry.     

Bioactive action of β‐glucosidase enzyme of Bifidobacterium longum upon isoflavone glucosides present in soymilk

Bioconversion of isoflavone glucosides and antioxidant activity by probiotic strain (Bifidobacterium longum) during soymilk fermentation was investigated, as well as partial characterisation of the produced enzyme β‐glucosidase. The enzyme has higher affinity for genistin than for other substrates assayed. Maximum activity occurred at 42 °C and at pH 6.0; keeping 70–80% of activity for 60 days stored at low temperatures. Bifidobacterium longum grew well in soymilk (8.26 log CFU mL^?1 and pH of 3.9 at 24 h) and were produced in good quantities of organic acids. High hydrolysis degree of isoflavone glucosides (81.2%) was observed at 24 h. Enhancements in bioactivity were assessed in fermented soymilk by monitoring the radical‐scavenging activity, antioxidant activity and DNA protective action. The use of probiotic Bifidobacterium strain as β‐glucosidase producer increased bioactive isoflavone content and demonstrated that this enzyme plays a key role in the bioavailability of soymilk isoflavones, reducing the bioconversion time compared to other studies.     

Antibacterial activity and mechanism of cinnamic acid and chlorogenic acid against Alicyclobacillus acidoterrestris vegetative cells in apple juice

The aim of this study was to investigate the antibacterial activity and mechanism of cinnamic acid and chlorogenic acid against Alicyclobacillus acidoterrestris. Minimum inhibitory concentrations of cinnamic acid and chlorogenic acid were 0.375 and 2.0 mg mL⁻¹, and the minimum bactericidal concentrations were 0.50 and 4.0 mg mL⁻¹, respectively. The apple juice ingredients had little influence on the inactivation of A. acidoterrestris. After treatment with cinnamic acid and chlorogenic acid, the morphology of A. acidoterrestris cells were severely destroyed; the leakage of nucleic acids and proteins increased significantly. SDS-PAGE investigation of bacterial proteins proved that the loss of soluble proteins was obvious as well. These results demonstrated that cinnamic acid and chlorogenic acid exerted their antibacterial activity mainly by an action mode of membrane disruption. This study provides an alternative method for the control of A. acidoterrestris-related spoilage in the fruit juice/beverage industry.     

Control of lactic acid bacteria in fermented beverages using lysozyme and nisin: test of traditional beverage boza as a model food system

The objective of this study was to increase quality and limited shelf‐life of boza (3–15 days), a traditional Balkan origin fermented beverage using lysozyme (LYS) and/or nisin (NIS). For this purpose, the effectiveness of NIS, LYS and LYS:NIS combinations was first tested in a broth medium at 4 °C for 3 weeks on Lactobacillus plantarum, one of the frequently isolated lactic acid bacteria in boza. Stability of LYS and NIS in boza, their effects on LAB counts, and chemical and sensory properties of boza were then evaluated during cold storage at 4 °C. Results of LAB counts as well as pH, d ‐ and l ‐lactic acid, and titratable acidity measurements showed that LAB in boza containing NIS (250 μg g^?1) or LYS:NIS (500:250 μg g^?1) could be controlled without reducing LAB counts below 6 log CFU mL^?1 during 2 weeks shelf‐life. In contrast, LYS (500 μg g^?1) alone could not control LAB in boza to delay its acidic spoilage. Positive effects of NIS and LYS:NIS application on quality of boza were also proved with sensory analysis by panelists and e‐nose measurements. This work showed that use of natural GRAS agents in preservation of fermented beverages containing probiotic LAB is possible without affecting their characteristic aroma and flavour.     

Synergistic effects of high pressure processing and slightly acidic electrolysed water on the inactivation of Bacillus cereus spores

Bacillus spores are concerns for their resistance to heat, high pressure processing (HPP), and disinfectants. We examined the effects of HPP and slightly acidic electrolysed water (SAEW) on inactivation of B. cereus spores. Spores' suspensions were prepared with 2‐(N‐morpholino) ethanesulfonic acid (MES) buffer or SAEW with available chlorine content (ACC) of 24, 35, 44 or 55 mg L^?1, and then subjected to HPP. The individual effects of HPP or SAEW on spores were negligible (<1.0 log CFU mL^?1). With factorial design and anova analysis, HPP + SAEW treatment was shown to have significantly positive effects on spores’ inactivation. The optimal conditions were 300 MPa HPP + SAEW with 44 mg L^?1 ACC or 200 MPa HPP + SAEW with 44 mg L^?1 ACC + 500 MPa HPP, producing reductions of 3.27 and 3.99 log CFU mL^?1, respectively. HPP + SAEW have potentials to serve as two effective hurdle techniques for inactivating B. cereus spores.     

Enzymatic grafting of gallate ester onto chitosan: evaluation of antioxidant and antibacterial activities

The antioxidant octyl gallate (OG) has been successfully grafted onto chitosan by means of horseradish peroxidase biocatalyst. The maximum gallate incorporation onto chitosan determined by ¹H NMR spectroscopy was up to 16 molar%. The resulting materials displayed antioxidant capacities with DPPH radical inhibition percentage up to 23% upon the assay conditions. The grafting of the antioxidant on chitosan enhanced its antimicrobial activity. Minimal inhibitory concentration (MIC) for Escherichia coli was 0.5 g L^?1. The native medium molecular weight chitosan alone or grafted with the lowest OG incorporation (ca. 11 molar%) attained 100% inhibition of E. coli, whereas lower inhibition was observed for all other materials 50.7–68.9% corresponding a reduction in the counts from 10.6 to 5.23–3.30 Log CFU mL^?1. The inhibition of Listeria monocytogenes was significantly higher (59.8–100%) than that with the Gram negative bacterium reaching the MIC at 0.25 g L^?1 with a reduction in the counts from 12.6 Log CFU mL^?1 to 5.06–0 Log CFU mL^?1.     

Mutation of Acetobacter pasteurianus by UV irradiation under acidic stress for high‐acidity vinegar fermentation

To obtain a mutant with higher vinegar production, a wild‐type industrial strain Acetobacter pasteurianus CICIM B7003 was pretreated in 50 g L^?1 acetic acid for 1 h and cultured for 12 h without adding any acetic acid; then, the enriched cells were mutated by UV under acidic stress (60 g L^?1 acetic acid). Using this method, A. pasteurianus CICIM B7003‐02, a mutant exhibiting best performance, was obtained. Notably, after repeated experiments, it was confirmed that B7003‐02 accumulated 103.81 ± 1.17 g L^?1 acetic acid within 160‐h batch cultivation in Erlenmeyer flasks, which was 49.2% higher than that of the wild type. Repeated batch fermentations with A. pasteurianus B7003‐02 were carried out for several runs in a Frings 8‐L acetator, and high‐acidity vinegars (90 ± 0.39 g L^?1) were produced. This work reveals the potential value for improvement in industrial vinegar production.