Effect of Various Encapsulating Materials on the Stability of Probiotic Bacteria

ABSTRACT:  Ten probiotic bacteria, including Lactobacillus rhamnosus , Bifidobacterium longum , L. salivarius , L. plantarum , L. acidophilus , L. paracasei , B. lactis type Bl-04, B. lactis type Bi-07, HOWARU L. rhamnosus , and HOWARU B. bifidum , were encapsulated in various coating materials, namely alginate, guar gum, xanthan gum, locust bean gum, and carrageenan gum. The various encapsulated probiotic bacteria were studied for their acid and bile tolerance. Free probiotic organisms were used as a control. The acid tolerance of probiotic organisms was tested at pH 2 over a 2-h incubation period. Bile tolerance was tested with taurocholic acid over an 8-h incubation period. The permeability of the capsules was also examined using a water-soluble dye, 6-carboxyflourescin (6-CF). The permeability was monitored by measuring the amount of 6-CF released from the capsules during a 2-w storage period. Results indicated that probiotic bacteria encapsulated in alginate, xanthan gum, and carrageenan gum survived better ( P < 0.05) than free probiotic bacteria, under acidic conditions. When free probiotic bacteria were exposed to taurocholic acid, viability was reduced by 6.36 log CFU/mL, whereas only 3.63, 3.27, and 4.12 log CFU/mL was lost in probiotic organisms encapsulated in alginate, xanthan gum, and carrageenan gum, respectively. All encapsulating materials tested released small amounts of 6-CF; however, alginate and xanthan gum retained 22.1% and 18.6% more fluorescent dye than guar gum. In general, microcapsules made of alginate, xanthan gum, and carrageenan gum greatly improved the survival of probiotic bacteria when exposed to acidic conditions and bile salts.     

Stability of Lactobacillus reuteri in Different Types of Microcapsules

This study was designed to find the most suitable method and wall material for microencapsulation of the probiotic bacterium Lactobacillus reuteri to maintain cell viability during gastric challenge. Five L. reuteri strains were individually encapsulated using alginate, alginate plus starch, K‐carrageenan with locust bean gum, or xanthan with gellan by extrusion or phase separation (emulsion). The morphology of the microcapsules was studied using phase contrast and cryo‐scanning electron microscopy (cryo‐SEM). The resistance of these microcapsules and the viability of contained L. reuteri to simulated gastric juice were studied. The shape and size of the microcapsules produced varied with the preparation method and type of wall material. Extruded microcapsules were larger and more uniformly shaped. Survival of microencapsulated L. reuteri was significantly better than that of planktonic cells and varied with the strain, method of microencapsulation, and wall material used. In general, microencapsulation using alginate and alginate with starch by both extrusion and phase separation were found to provide bacteria significantly greater protection (P < 0.05) against simulated gastric juice.     

Storage Stability of Lactobacillus paracasei as Free Cells or Encapsulated in Alginate-Based Microcapsules in Low pH Fruit Juices

The main objective of this research effort was to study whether microencapsulation could be a viable alternative to obtain probiotic orange or peach juices. In order to be considered probiotic food, probiotic bacteria must be present in sufficient viable numbers to promote a benefit to the host. The survival and viability of Lactobacillus paracasei L26 in juices over 50?days of storage at 5°C was assessed, evaluating the potential use of encapsulated cells in alginate microcapsules. L. paracasei L26 demonstrated good viability in both orange and peach juices despite the low pH values of both juices. Microencapsulation in alginate, with or without double coating, revealed to be suitable to protect L. paracasei L26 since viable cells were approximately 9 log cfu/g after 50?days of storage at 5°C. In general, the probiotic fruit juices showed a decrease in pH during storage. Glucose and fructose contents as well as citric acid contents decreased during storage, whereas an increase in formic acid was observed. The outcome of this study points to L. paracasei L26 as having promising potential, especially in an encapsulated form, as functional supplements in fruit juices without dairy ingredients due to their tolerance in an acidic environment over 50?days of storage at 5°C. Further studies are warranted to prove the functionality of juices with encapsulated probiotic strains.     

Stability of free and encapsulated Lactobacillus acidophilus ATCC 4356 in yogurt and in an artificial human gastric digestion system

The objective of this study was to determine the effect of encapsulation on survival of probiotic Lactobacillus acidophilus ATCC 4356 (ATCC 4356) in yogurt and during artificial gastric digestion. Strain ATCC 4356 was added to yogurt either encapsulated in calcium alginate or in free form (unencapsulated) at levels of 8.26 and 9.47 log cfu/g, respectively, and the influence of alginate capsules (1.5 to 2.5 mm) on the sensorial characteristics of yogurts was investigated. The ATCC 4356 strain was introduced into an artificial gastric solution consisting of 0.08 N HCl (pH 1.5) containing 0.2% NaCl or into artificial bile juice consisting of 1.2% bile salts in de Man, Rogosa, and Sharpe broth to determine the stability of the probiotic bacteria. When incubated for 2 h in artificial gastric juice, the free ATCC 4356 did not survive (reduction of > 7 log cfu/g). We observed, however, greater survival of encapsulated ATCC 4356, with a reduction of only 3 log cfu/g. Incubation in artificial bile juice (6 h) did not significantly affect the viability of free or encapsulated ATCC 4356. Moreover, statistically significant reductions (~1 log cfu/g) of both free and encapsulated ATCC 4356 were observed during 4-wk refrigerated storage of yogurts. The addition of probiotic cultures in free or alginate-encapsulated form did not significantly affect appearance/color or flavor/odor of the yogurts. However, significant deficiencies were found in body/texture of yogurts containing encapsulated ATCC 4356. We concluded that incorporation of free and encapsulated probiotic bacteria did not substantially change the overall sensory properties of yogurts, and encapsulation in alginate using the extrusion method greatly enhanced the survival of probiotic bacteria against an artificial human gastric digestive system.     

Calcium alginate‐resistant starch mixed gel improved the survival of Bifidobacterium animalis subsp. lactis Bb12 and Lactobacillus rhamnosus LBRE‐LSAS in yogurt and simulated gastrointestinal conditions

The aim of this study was to investigate the protective effect of microencapsulation in calcium alginate‐resistant starch mixed gel of a new human isolated strain of Lactobacillus rhamnosus LBRE‐LSAS compared with the probiotic strain of Bifidobacterium animalis subsp. lactis Bb12. Influence of microencapsulation was tested under deleterious digestive environment, when challenged to salivary α‐amylase, to simulated gastric fluid and to simulated intestinal fluid. Bacterial survival, post‐acidifying activity and exopolysaccharides (EPS) content in stored mix yogurt were assessed. Integrity of the beads was acceptable under α‐amylase levels largely higher than those found in human saliva. Under simulated gastrointestinal model, viable cell counts of encapsulated cells were significantly higher than those observed with free cells and remained at the recommended levels. Additionally, microencapsulation allowed an improved viability of bacteria and generated higher EPS amounts in mix yogurt stored at 4 °C. Our results indicate that calcium alginate‐resistant starch beads extend survival under digestive conditions and in yogurt and could be used as an efficient delivery system for probiotics.     

Preparation of Acid‐Resistant Microcapsules with Shell‐Matrix Structure to Enhance Stability of Streptococcus Thermophilus IFFI 6038

Microencapsulation is an effective technology used to protect probiotics against harsh conditions. Extrusion is a commonly used microencapsulation method utilized to prepare probiotics microcapsules that is regarded as economical and simple to operate. This research aims to prepare acid‐resistant probiotic microcapsules with high viability after freeze‐drying and optimized storage stability. Streptococcus thermophilus IFFI 6038 (IFFI 6038) cells were mixed with trehalose and alginate to fabricate microcapsules using extrusion. These capsules were subsequently coated with chitosan to obtain chitosan‐trehalose‐alginate microcapsules with shell‐matrix structure. Chitosan‐alginate microcapsules (without trehalose) were also prepared using the same method. The characteristics of the microcapsules were observed by measuring the freeze‐dried viability, acid resistance, and long‐term storage stability of the cells. The viable count of IFFI 6038 in the chitosan‐trehalose‐alginate microcapsules was 8.34 ± 0.30 log CFU g^?1 after freeze‐drying (lyophilization), which was nearly 1 log units g^?1 greater than the chitosan‐alginate microcapsules. The viability of IFFI 6038 in the chitosan‐trehalose‐alginate microcapsules was 6.45 ± 0.09 log CFU g^?1 after 120 min of treatment in simulated gastric juices, while the chitosan‐alginate microcapsules only measured 4.82 ± 0.22 log CFU g^?1. The results of the long‐term storage stability assay indicated that the viability of IFFI 6038 in chitosan‐trehalose‐alginate microcapsules was higher than in chitosan‐alginate microcapsules after storage at 25 °C. Trehalose played an important role in the stability of IFFI 6038 during storage. The novel shell‐matrix chitosan‐trehalose‐alginate microcapsules showed optimal stability and acid resistance, demonstrating their potential as a delivery vehicle to transport probiotics.     

Survival of free and encapsulated probiotic bacteria and their effect on the sensory properties of yoghurt

The survival and effect of free and calcium-induced alginate-starch encapsulated probiotic bacteria (Lactobacillus acidophilus and Bifidobacterium lactis) on pH, exopolysaccharide production and influence on the sensory attributes of yogurt were studied over 7 weeks storage. Addition of probiotic bacteria (free or encapsulated) reduced acid development in yogurt during storage. Post-acidification in yogurt with encapsulated probiotic bacteria was slower compared to yogurt with free probiotic bacteria. More exopolysaccharides were observed in yogurts with probiotic cultures compared to those without probiotic cultures. The results showed that there was an increased survival of 2 and 1 log cell numbers of L. acidophilus and B. lactis, respectively due to protection of cells by microencapsulation. The addition of probiotic cultures either in the free or encapsulated states did not significantly affect appearance and colour, acidity, flavour and after taste of the yogurts over the storage period. There were, however, significant differences (P<0.05) in the texture (smoothness) of the yogurts. This study has shown that incorporation of free and encapsulated probiotic bacteria do not substantially alter the overall sensory characteristics of yogurts and microencapsulation helps to enhance the survival of probiotic bacteria in yogurts during storage.     

Viability,Acid and Bile Tolerance of Spray Dried Probiotic Bacteria and Some Commercial Probiotic Supplement Products Kept at Room Temperature

Production of probiotic food supplements that are shelf‐stable at room temperature has been developed for consumer's convenience, but information on the stability in acid and bile environment is still scarce. Viability and acid and bile tolerance of microencapsulated Bifidobacterium spp. and Lactobacillus acidophilus and 4 commercial probiotic supplements were evaluated. Bifidobacterium and L. acidophilus were encapsulated with casein‐based emulsion using spray drying. Water activity (a_w) of the microspheres containing Bifidobacterium or L. acidophilus (SD GM product) was adjusted to 0.07 followed by storage at 25 °C for 10 wk. Encapsulated Bifidobacterium spp. and Lactobacillus acidophilus and 4 commercial probiotic supplement products (AL, GH, RE, and BM) were tested. Since commercial probiotic products contained mixed bacteria, selective media MRS‐LP (containing L‐cysteine and Na‐propionate) and MRS‐clindamycin agar were used to grow Bifidobacterium spp. or L. acidophilus, respectively, and to inhibit the growth of other strains. The results showed that a_w had a strong negative correlation with the viability of dehydrated probiotics of the 6 products. Viable counts of Bifidobacterium spp. and L. acidophilus of SD GM, AL, and GH were between 8.3 and 9.2 log CFU/g, whereas that of BM and RE were between 6.7 and 7.3 log CFU/g. Bifidobacterium in SD GM, in AL, and in GH products and L. acidophilus in SD GM, in AL, and in BM products demonstrated high tolerance to acid. Most of dehydrated probiotic bacteria were able to survive in bile environment except L. acidophilus in RE product. Exposure to gastric juice influenced bacterial survivability in subsequent bile environment.     

Acid, bile, and heat tolerance of free and microencapsulated probiotic bacteria

ABSTRACT:  Eight strains of probiotic bacteria, including Lactobacillus rhamnosus , Bifidobacterium longum, L. salivarius, L. plantarum , L. acidophilus , L. paracasei , B. lactis type Bl-O4, and B. lactis type Bi-07, were studied for their acid, bile, and heat tolerance. Microencapsulation in alginate matrix was used to enhance survival of the bacteria in acid and bile as well as a brief exposure to heat. Free probiotic organisms were used as a control. The acid tolerance of probiotic organisms was tested using HCl in MRS broth over a 2-h incubation period. Bile tolerance was tested using 2 types of bile salts, oxgall and taurocholic acid, over an 8-h incubation period. Heat tolerance was tested by exposing the probiotic organisms to 65 °C for up to 1 h. Results indicated microencapsulated probiotic bacteria survived better ( P < 0.05) than free probiotic bacteria in MRS containing HCl. When free probiotic bacteria were exposed to oxgall, viability was reduced by 6.51-log CFU/mL, whereas only 3.36-log CFU/mL was lost in microencapsulated strains. At 30 min of heat treatment, microencapsulated probiotic bacteria survived with an average loss of only 4.17-log CFU/mL, compared to 6.74-log CFU/mL loss with free probiotic bacteria. However, after 1 h of heating both free and microencapsulated probiotic strains showed similar losses in viability. Overall microencapsulation improved the survival of probiotic bacteria when exposed to acidic conditions, bile salts, and mild heat treatment.     

Probiotic potential and biochemical and technological properties of Lactococcus lactis ssp. lactis strains isolated from raw milk and kefir grains

Lactococcus lactis ssp. lactis is one of the most important starter bacteria used in dairy technology and it is of great economic importance because of its use in the production of dairy products, including cheese, butter, cream, and fermented milks. Numerous studies have evaluated the biochemical and probiotic properties of lactococci; however, limited studies on the probiotic characteristics of lactococci were conducted using strains originating from raw milk and dairy products. Characterizing the probiotic properties of strains isolated from raw milk and fermented milk products is important in terms of selecting starter culture strains for the production of functional dairy products. In this study, biochemical properties (including antibiotic sensitivity, lipolytic activity, amino acid decarboxylation, antioxidant activity) and probiotic properties (including antimicrobial activity, growth in the presence of bile salts, bile salts deconjugation, and hydrophobicity) of 14 Lactococcus lactis strains isolated from raw milk and kefir grains were investigated. Strains originating from kefir grains had better characteristics in terms of antimicrobial activity and bile salt deconjugation, whereas strains from raw milk had better hydrophobicity and antioxidant activity characteristics. None of the strains were able to grow in the presence of bile salt and did not show amino acid decarboxylation or lipolytic activities. Biochemical and probiotic properties of L. lactis strains varied depending on the strain and some of these strains could be used as functional cultures depending on their properties. However, these strains did not possess all of the properties required to meet the definition of a probiotic.     

Encapsulation in an alginate–goats’ milk–inulin matrix improves survival of probiotic Bifidobacterium in simulated gastrointestinal conditions and goats’ milk yoghurt

In this work, a new encapsulating matrix, alginate–goats’ milk–inulin, was used to encapsulate Bifidobacterium animalis subsp. lactis BB‐12. The addition of inulin resulted in capsules with a compact structure, and a higher probiotic cell count under simulated gastrointestinal conditions and in probiotic goats’ milk yoghurt during refrigerated storage. Encapsulation of the probiotic bacteria led to slower post‐acidification yoghurts. The results of this study showed that the alginate–goats’ milk–inulin matrix has potential to be used as a new encapsulation material to encapsulate probiotics for use in goats’ milk‐based probiotic fermented dairy products, avoiding the cross‐contamination caused by using capsules based on cows’ milk.     

Descriptive analysis of bacterial profile,physicochemical and sensory characteristics of grape juice containing Saccharomyces cerevisiae cell wall‐coated probiotic microcapsules during storage

In this study the feasibility of incorporation of probiotic microcapsules coated with fragmented yeast cell wall in grape juice was evaluated during 60 days at 4 °C. Lactobacillus acidophilus and Bifidobacterium bifidum were encapsulated in alginate microbeads and coated with fragmented Saccharomyces cerevisiae cell wall and calcium alginate and were added into grape juice. At the end of storage, the survival of probiotics was higher than recommended minimum value (10⁷ cfu mL^?1) and the results demonstrated that applying yeast cell wall layer for L. acidophilus microcapsules significantly enhanced its survival while did not affect the survival of B. bifidum (P > 0.05). Generally, probiotic grape juice showed decrease in °Brix, pH and colour and increase in acidity and turbidity during storage and the presence of yeast wall layer had no significant effect on its properties expect colour and turbidity. Overall acceptance of grape juices containing yeast cell wall‐coated microcapsules scored the least.     

Promoting Lactobacillus casei and Bifidobacterium adolescentis survival by microencapsulation with different starches and chitosan and poly L‐lysine coatings in ice cream

In this research, microencapsulation of the probiotics Lactobacillus casei ATCC 39392 and Bifidobacterium adolescentis ATCC 15703 was performed using calcium alginate, wheat, rice, and high‐amylose corn (Hylon VII) starches along with chitosan and poly L‐lysine coatings. The effect of microencapsulation on the survival and sensory properties of ice cream over 100 days at ?30 °C was evaluated. Scanning electron and optical microscopy were employed to measure capsule size and morphology. The results suggested that the survival of probiotics is increased by microencapsulation. Coating the capsules with chitosan and poly L‐lysine led to enhanced bacterial viability and an increase in the size of microcapsules. Among different starches, Hylon starch enhanced the survival of probiotics at low temperatures the most. Furthermore, the addition of probiotics in free and encapsulated states did not have a significant effect on the sensory properties, or pH levels of the final product during storage (p > .05).

Practical applications

Microencapsulation using various hydrocolloids is a commonly used method for enhancing probiotic survival in ice cream during the frozen storage. This study indicates that the microencapsulation of probiotics can enhance probiotic survival in ice cream after 100 days of storage at ?30 °C. Chitosan and poly L‐lysine coatings significantly improved the survival of encapsulated probiotics during the storage of ice cream. This improvement is attributed to the role of Hylon starch in creating more integrated microcapsule structure. Moreover, sensory evaluation of ice cream revealed that inoculation with the probiotic culture, in either the encapsulated or the free‐state, had no significant effect on texture, color, flavor, taste, or general sensory characterization of ice cream during the storage period at ?30 °C (p > .05).     

Protecting probiotic bacteria by microencapsulation: challenges for industrial applications

The use of probiotic bacteria in novel foods to provide beneficial health effects is today of increasing interest in the food industry. The process stability of probiotics is, however, not always optimal. Microencapsulation technology can be used to maintain the viability of probiotic bacteria during food product processing and storage. Both true microcapsules with coating as well as microspheres where the bacteria are evenly spread in the coating material are discussed. It is important that encapsulation keeps the probiotics active through the gastrointestinal tract and releases them in their target organ. The survival of microencapsulated cells in simulated gastric conditions is therefore also reviewed. Polysaccharides like alginate, gellan, κ-carrageenan and starch are the most commonly used materials in microencapsulation of bifidobacteria and lactobacilli. Techniques commonly applied for probiotic microencapsulation are emulsion, extrusion, spray drying, and adhesion to starch. Bead stability can be improved by using different coating materials, e.g. chitosan. Future challenges in the field include recognition of new potent applications, selection of appropriate techniques, materials and bacterial strains, and minimizing the extra costs incurred by microencapsulation.     

Effects of encapsulation on the viability of probiotic strains exposed to lethal conditions

The effect of microencapsulation on the viability of Lactobacillus casei, L. paracasei, L. acidophilus Ki and Bifidobacterium animalis BB‐12 during exposure to lethal conditions (25% NaCl, pH 3.0 and 55–60 °C) was evaluated. Results demonstrated that survival of probiotic strains to the imposed lethal stress conditions was strain dependent. With the exception of exposure to 25% (w/v) NaCl, L. acidophilus Ki (free and encapsulated cells) demonstrated the highest survival rates through exposure to lethal conditions of temperature and pH. For this probiotic strain exposed to heat, microencapsulated cells expressed a higher heat tolerance at 55 °C than free cells. For the other tested bacteria, in general, encapsulation had no positive effect on survival through the tested lethal conditions.     

Assessment of probiotic characteristics of lactic acid bacteria isolated from fermented yak milk products of Sikkim,India: Chhurpi,Shyow, and Khachu

The present study documents the probiotic attributes of indigenous lactic acid bacteria (LAB) isolated from local fermented Yak milk products namely Chhurpi, Shyow and Khachu prepared in the northern and eastern region of Sikkim in the Himalayas. Samples were collected aseptically and a total of 170 LAB was isolated and screened for putative probiotic properties like hypocholesteromic effect, acid tolerance, bile tolerance, bile salt hydrolase (BSH) activity and cell surface hydrophobicity. It was observed that 70 LAB isolates showed cholesterol lowering activity, out of which 35 isolates were selected that showed 50% and less cholesterol reducing effect in vitro. Acid tolerance test revealed good tolerance of 12 isolates at pH 2.5 and pH 2.0 for up to 2 hours. The tolerance to 0.5% and 1% of three bile salts acid revealed more growth in MRS broth containing taurocholic acid with the isolates revealing good BSH activity leading to bile acid deconjugation. The cell surface hydrophobicity ranged from 20–95%. Furthermore, 16S rRNA gene sequencing revealed Lactobacillus plantarum YD5S and YD9S, L. pentosus YD8S, L. paraplantarum YD11S, Enterococcus lactis YHC20 and E. faecium YY1 as the best isolates with technological properties. The isolates may serve as potential probiotic candidates with potential for hypocholesteromic benefits in the future.     

Effect of KCl substitution on bacterial viability of Escherichia coli (ATCC 25922) and selected probiotics

Excessive intake of NaCl has been associated with the increased risk of several diseases, particularly hypertension. Strategies to reduce sodium intake include substitution of NaCl with other salts, such as KCl. In this study, the effects of NaCl reduction and its substitution with KCl on cell membranes of a cheese starter bacterium (Lactococcus lactis ssp. lactis), probiotic bacteria (Bifidobacterium longum, Lactobacillus acidophilus, and Lactobacillus casei), and a pathogenic bacterium (Escherichia coli) were investigated using Fourier-transform infrared (FTIR) spectroscopy. A critical NaCl concentration that inhibited the viability of E. coli without affecting the viability of probiotic bacteria significantly was determined. To find the critical NaCl concentration, de Man, Rogosa, and Sharpe (MRS) broth was supplemented with a range of NaCl concentrations [0 (control), 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, and 5.0%], and the effect on cell viability and FTIR spectra was monitored for all bacteria. A NaCl concentration of 2.5% was found to be the critical level of NaCl to inhibit E. coli without significantly affecting the viability of most of the probiotic bacteria and the cheese starter bacterium. The FTIR spectral analysis also highlighted the changes that occurred mainly in the amide regions upon increasing the NaCl concentration from 2.5 to 3.0% in most of the bacteria. Escherichia coli and B. longum were more sensitive to substitution of NaCl with KCl, compared with Lb. acidophilus, Lb. casei, and Lc. lactis ssp. lactis. To evaluate the effect of substitution of NaCl with KCl, substitution was carried out at the critical total salt concentration (2.5%, wt/vol) at varying concentrations (0, 25, 50, 75, and 100% KCl). The findings suggest that 50% substitution of NaCl with KCl, at 2.5% total salt, could inhibit E. coli without affecting the probiotic bacteria.     

Usefulness of a set of simple in vitro tests for the screening and identification of probiotic candidate strains for dairy use

A set of simple in vitro tests (identification by species-specific PCR, genetic diversity, phage sensitivity, growth and viability in milk, resistance to salts and flavor compounds, bacterial interactions, tolerance to simulated gastric juice and bile, bile salts deconjugation, hydrophobicity and β-galactosidase and antibacterial activities), that can be carried out in almost every laboratory of microbiology, mainly in developing countries where there is often limited access to sophisticated techniques, allowed us to identify, among 19 intestinal human isolates, a potential candidate for new probiotic dairy foods for the local market. Lactobacillus gasseri LgF_37/1 performed well in the culture media used for the enumeration of probiotic bacteria in argentinian dairy products. This strain showed also high tolerance to the technological challenges assessed, bile salts resistance, the capacity to produce bacteriocin-like metabolites, to inhibit pathogenic bacteria, to deconjugate bile salts and high hydrophobicity. Further in vivo research should be carried out with this strain before claiming probiotic properties for it. However, the use of a set of simple in vitro techniques proved to be important to determine which strains should undergo future and more complex studies.     

Effect of microencapsulation and resistant starch on the probiotic survival and sensory properties of synbiotic ice cream

Two types of synbiotic ice cream containing 1% of resistant starch with free and encapsulated Lactobacillus casei (Lc-01) and Bifidobacterium lactis (Bb-12) were manufactured. The survival of L. casei and B. lactis were monitored during the product’s storage for 180 days at −20 °C. The viable cell number of L. casei and B. lactis in the free state in prepared ice cream mixture was 5.1 × 10⁹ and 4.1 × 10⁹ CFU/mL at day one and after 180 days storage at −20 °C, these numbers were decreased to 4.2 × 10⁶ and 1.1 × 10⁷ CFU/mL, respectively. When we encapsulated the mentioned probiotic bacteria in calcium alginate beads, the probiotic survival raised at rate of 30% during the same period of storage at same temperature. In general, the results indicated that encapsulation can significantly increase the survival rate of probiotic bacteria in ice cream over an extended shelf-life. The addition of encapsulated probiotics had no significant effect on the sensory properties of non-fermented ice cream in which we used the resistant starch as prebiotic compound.     

Enhancing the Biotransformation of Isoflavones in Soymilk Supplemented with Lactose Using Probiotic Bacteria during Extended Fermentation

ABSTRACT: Soymilk (SM) lacks lactose; hence supplementation of SM with lactose is likely to enhance the growth of probiotic bacteria and biotransformation of isoflavone glycosides to isoflavone aglycones. In this study, 11 strains of probiotic bacteria including Lactobacillus rhamnosus, L. salivarius, L. plantarum, L. acidophilus, L. paracasei, HOWARU L. rhamnosus, L. delbrueckii subsp. bulgaricus, Bifidobacterium lactis type Bi-07, B. longum, HOWARU B. bifidum, and B lactis type Bi-04 were inoculated individually or as mixed cultures into SM and soymilk supplemented with lactose (SML). A total of 2% of lactose was added to 1 L of SM with the aim of improving the growth of probiotic organisms and promoting the biotransformation of isoflavone isomers to bioactive isoflavone aglycomes. Samples of SM were incubated at 37 °C and 10 mL aliquots of SM were taken at 0, 24, 48, and 72 h to monitor the growth of probiotic bacteria and changes in isoflavone contents using high-performance liquid chromatography (HPLC). Results indicated that SML fermented with probiotics had higher viable counts by >2.4 log CFU/mL than that in SM at the end of the 72 h fermentation period. Mixed cultures grew at different rates and in general Lactobacilius spp. had >1.02 log CFU/mL more cells than Bifidobacterium spp. at the end of the fermentation period. The total aglycone content in SM at 72 h of fermentation was 0.924 mg/100 mL, whereas that in SML was 1.623 mg/100 mL. Addition of lactose not only improved the growth of probiotic bacteria in SM but also enhanced the biotransformation of isoflavone glucosides to the more bioactive isoflavone aglycones. Mixed cultures did not improve the biotransformation of bioactive isoflavones when compared to single cultures.