Survival and activity of selected probiotic organisms in set-type yoghurt during cold storage

The growth and metabolism of two probiotic organisms (L. acidophilus LAFTI^® L10 and Lactobacillus casei LAFTI^® L26) and a regular yoghurt culture (L. delbrueckii ssp. bulgaricus Lb1466 and Streptococcus thermophilus St1342) were studied in yoghurt containing 0.5%, 1.0%, and 1.5% (w/v) of high amylose corn starch powder (Hi-maize^®) or inulin. Viable cell counts of probiotic organisms, their metabolites and proteolytic activities, and viscosity of the yoghurts were determined during refrigerated storage for 28 d at 4 ^oC. In the presence of inulin, cultures showed better retention of viability (8.0 log cfu g⁻¹) in comparison with that of Hi-maize, which had a reduction by one log cycle. Lower concentrations of 0.5–1.0% Hi-maize improved (P<0.05) the production of propionic acid and also increased proteolytic activity of probiotic organisms substantially. A greater release of free amino acids may have sustained better growth of the organisms in yoghurts. Supplementation with either Hi-maize or inulin increased the viscosity of probiotic yoghurts significantly (P<0.05).     

Effect of packaging materials and dissolved oxygen on the survival of probiotic bacteria in yoghurt

The effects of packaging materials on the dissolved oxygen and the survival of the probiotic bacteria in yoghurt were studied. Oxygen adapted and non‐oxygen adapted strains of Lactobacillus acidophilus and Bifidobacterium spp. were incorporated in yoghurts, which were packaged in oxygen permeable high‐impact polystyrene (HIPS), oxygen‐barrier material (Nupak^TM) and Nupak^TM with an oxygen scavenging film (Zero₂^TM). During storage the dissolved oxygen increased steadily in HIPS packaged yoghurt whereas it remained low in yoghurts packaged in Nupak^TM and Zero₂^TM. In all yoghurts, no significant decreases were observed in the viability of either oxygen adapted or non‐oxygen adapted cells of L. acidophilus and Bifidobacterium spp. Thus, although the dissolved oxygen in yoghurt can be influenced by the type of packaging material, it may not affect the survival of probiotic bacteria in yoghurts.     

Rheology,spontaneous whey separation,microstructure and sensorial characteristics of probiotic yoghurts enriched with passion fruit fiber

Beyond demonstrated beneficial health attributes, passion fruit rinds are a by-product of the fruit pulp industry, rich in total dietary fiber, particularly pectin. The aim of this study was to evaluate the influence of the addition of passion fruit fiber on the whey formation, rheological parameters, microstructure and sensorial characteristics of probiotic yoghurts. Skim milk bases enriched with 1% of passion fruit fiber or not were heat treated and inoculated with Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, and divided into four groups according to the probiotic strain added — Lactobacillus acidophilus strains L10 and NCFM and Bifidobacterium animalis subsp. lactis strains Bl04 and B94. Fermentations were performed until the pH reached 4.5. Rheological characteristics of yoghurts were determined by a rotational rheometer in two cycles of shear rate ranging from 0 to 15 s^? 1 in both upward and downward curves. Sensorial analysis of passion fruit fiber yoghurts, either without any probiotic or co-fermented by L. acidophilus L10 or B. animalis subsp. lactis Bl04, was evaluated against a control yoghurt without fiber. Photomicrographs of freeze-dried yoghurts were made by field-emission scanning electron microscope (SEM). Thixotropy of enriched yoghurts was higher than that of their respective controls in the two cycles of shear rate. Apparent viscosity was significantly higher in fiber yoghurts co-fermented by the lactobacilli than in their controls at the end of cold storage. Photomicrographs demonstrated that in passion fruit fiber yoghurts the casein gel was more compact and overlaid the fiber, while filaments of exopolysaccharides were more frequent in control yoghurts. Appearance, odor and color of the passion fruit fiber yoghurts received scores as ‘good’, and the intensity of the passion fruit flavor was considered weak by the sensory assessors. Results indicate that the passion fruit fiber is an almost neutral ingredient for the design of new high value-added yoghurt.     

Effect of long‐chain inulin on the texture profile and survival of Lactobacillus paracasei ssp. paracasei in set yoghurts during refrigerated storage

The effects of adding inulin at 20 g/L as a fat replacer and probiotic bacteria on the physicochemical and textural characteristics of yoghurt were studied. The ability of long‐chain inulin to improve the probiotic (Lactobacillus paracasei ssp. paracasei) bacteria viability in yoghurt was investigated. The addition of inulin made the texture (firmness, cohesiveness, adhesiveness and gumminess) of skimmed yoghurt similar to that of whole yoghurt, demonstrating the role of inulin as a fat replacer. However inulin increased syneresis and did not influence the viability of probiotic bacteria in the yoghurts. The addition of probiotic bacteria in yoghurts improved syneresis and increased firmness and gumminess.     

Innovative production of multistrain synbiotic product using Thai-pigmented rice and rice bran oil

This study found that the isolated probiotics Lactobacillus paracasei KUKPS6201, L. acidophilus KUKPS6107, L. reuteri KUKPS6103, L. rhamnosus KUKPS6007, L. salivarius KUKPS6202, Bacillus coagulans KPSTF02 and Saccharomyces boulardii KUKPS6005 had high potential for probiotic properties. All strains had antibacterial activity and high antioxidant activity of 1.654 ± 0.017 mg Trolox mL⁻¹ probiotic extract. The selected strains could survive in a simulated gastrointestinal tract under anaerobic conditions and showed no haemolytic activity. Furthermore, the probiotic strains were strongly auto-aggregated and also showed co-aggregated ability with pathogenic bacteria. The probiotic microorganisms demonstrated high ability to adhere to Thai-pigmented rice grains. The results of analysis of these probiotics showed that Riceberry rice bran oil was an excellent prebiotic. A synbiotic product containing Thai-pigmented rice grains (cultivar Riceberry, Luem Pua and Black Jasmine) and rice bran oil was produced. After 8 weeks of storage, the viability of the probiotics in terms of multistrains was 7.36 ± 0.04 log CFU g^–1 (85.78% survival rate). Microbiological safety testing indicated that the amounts of contaminants were acceptable. This study provided the first scientific report on the feasibility of applying Thai-pigment rice, rice bran oil and mixed-culture probiotics as a novel functional synbiotic product.     

Survival of Lactobacillus casei and functional characteristics of reduced sugar red beetroot yoghurt with natural sugar substitutes

In this study, probiotic gel fermentation and functional characteristics of reduced sugar yoghurt with red beetroot bioactive components and steviol glycosides from Stevia rebaudiana extracts as natural source of noncaloric sweeteners were investigated. A significant increase in Lactobacillus casei viability and fermented gel network and a decrease in syneresis were determined in yoghurt sweetened with steviol glycosides and high content of red beetroot bioactive components such as total phenolics, anthocyanins and total antioxidant capacity (DPPH and FRAP). The survival of L. casei was maintained within probiotic and therapeutic levels (>9 log₁₀ CFU/g), due to the possible prebiotic effect of steviol glycosides and fermentable fibres and phenolic compounds of red beetroot during 28 days of cold storage of the probiotic yoghurts. Colour properties (L*, a*, b*, ΔE*, C*, h*) and such sensory properties as smoothness, sweetness astringency were significantly affected. The highest organic acid content was found in red beetroot enriched yoghurt with stevia, while the most dominant organic acids were butyric, lactic, malic and citric. As a result, it was determined that fermented milk products, which are supported by phytochemical and steviol glycoside interactions, have adequate nutritional effects, high probiotic viability and acceptable sensory properties     

Performance of different microbial cultures in potentially probiotic and prebiotic yoghurts from cow and goat milks

Lactobacillus acidophilus or Bifidobacterium animalis subsp. lactis Bb‐12 and green banana pulp were used in order to obtain potentially probiotic and prebiotic yoghurts, which were compared over a 45‐day storage period. Goat milk yoghurts demonstrated probiotic effects up to 45 days of storage. Cow milk yoghurts produced with B. animalis subsp. lactis Bb‐12 showed a probiotic effect reduction during the storage period (1.74 log CFU/g). The type of milk affected the yoghurts’ chemical and physicochemical properties. Sensory acceptance was also affected, where cow milk yoghurts were better accepted than goat milk ones.     

Effect of cryoprotectants,prebiotics and microencapsulation on survival of probiotic organisms in yoghurt and freeze-dried yoghurt

The survival of probiotic microorganisms including Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus rhamnosus and Bifidobacterium spp. was evaluated in yoghurt and freeze-dried yoghurt after processing and storage. The effectiveness of microencapsulating probiotic organisms as well as adding cryoprotectants and prebiotics in improving their viability was also investigated. The viability of Bifidobacterium infantis 17930 and L. rhamnosus GG was reduced by 0.07 log, while that of L. casei 1520 and Bifidobacterium longum 1941 was reduced by 0.28 and 0.39 log, respectively. There was a 7% improvement in the viability of L. casei 1520 when cryoprotectant ‘Unipectine™ RS 150’ was added at 2.5% (w/v). The prebiotic ‘Raftilose^®P95’ when added at 1.5% w/v to yoghurt improved the viability of the combined selected probiotic organisms by 1.42 log during four weeks of storage at 4 °C. Microencapsulation with alginate improved viability of combined selected probiotic organisms by 0.31 log in freeze-dried yoghurt stored at 21 °C.     

Shelf life and quality of probiotic yogurt produced with Lactobacillus acidophilus and Gobdin

This study evaluated the effect of dry white mulberry and walnut paste (Gobdin, a traditional Turkish food) in probiotic yogurt on the survival of Lactobacillus acidophilus and yogurt properties. Six different yogurts were produced with 0%, 5% and 10% Gobdin using Lactobacillus bulgaricus + Streptococcus thermophilus and with 0%, 5% and 10% Gobdin using L. bulgaricus + S. thermophilus + L. acidophilus. The physical, chemical, microbiological and sensorial properties of the yogurts were evaluated based on storage at 4 ± 1 °C. Probiotic shelf life and the most suitable combinations were determined. The highest L. acidophilus count (8.65 log cfu g^?1) was found in the 5% Gobdin‐supplemented yogurt on the 7th day of storage, while the lowest count (8.11 log cfu g^?1) was found in the probiotic control yogurt on the 21st day. Although the L. acidophilus counts in the probiotic yogurts declined during storage, all values found throughout the 21‐day storage period were >8 log cfu g^?1. This is above the level necessary to provide the desired therapeutic effect in probiotic products (10⁶–10⁷ cfu g^?1). The highest overall acceptability score was obtained on the first day from the yogurt with 5% Gobdin. However, all yogurt samples had general acceptability scores between 7 and 8 points from a 9‐point maximum. Thus, this study determined that a new functional yogurt can be produced using L. acidophilus with 5% Gobdin.     

Stevia‐fortified yoghurt: Stability,antioxidant activity and in vitro digestion behaviour

In this study, yoghurt samples were fortified with 0.25% and 0.5% freeze‐dried stevia extract (FSE). The control and stevia‐fortified yoghurts were evaluated and compared for the viability of the starter cultures, physicochemical properties, total phenolic content (TPC) and antioxidant activity throughout 30 days of storage. In addition, TPC and antioxidant activity were evaluated during in vitro gastrointestinal digestion. The results showed that the yoghurt matrix preserved the TPC, antioxidant capacity and total solids during storage, while the acidity, synaeresis and counts of the starter cultures of the final product were not significantly affected. However, addition of 0.5% FSE exerted a buffering effect on the system. After simulated digestion, the values of TPC and antioxidant activity of the fortified yoghurts increased in relation to the undigested fractions. These findings showed the feasibility of employing FSE as a functional ingredient in the manufacture of yoghurts with potential antioxidant properties.     

Encapsulation increases the in vitro bioaccessibility of probiotics in yoghurt

This study examined the encapsulation efficacy of probiotics in yoghurts, product physicochemical properties, the best timing to add encapsulated probiotics during yoghurt manufacturing (before or after fermentation) and their in vitro bioaccessibility. Three different yoghurt types were produced including plain and with encapsulated probiotics added before and after fermentation. A significant (P < 0.05) reduction in total probiotic count was observed in yoghurts containing encapsulated probiotics after 21 days of refrigerated storage. However, the total probiotic count increased during the in vitro colonic fermentation when yoghurts containing encapsulated probiotics were used, indicating increased bioaccessibility of probiotics in the colon.     

Survival of probiotic microflora in Argentinian yoghurts during refrigerated storage

The survival of Bifidobacterium bifidum BBI and Lactobacillus acidophilus LAI in reduced-fat (liquid) and full-fat (set) yoghurts produced with two commercial lactic starter cultures (SID and SISD) was investigated. The viability of the probiotic bacteria was also assayed in milk acidified with lactic acid at different pH values. Samples were stored at 5°C for up to 4 weeks. There was a great variability in the survival ability of the probiotic cultures in the two yoghurt types. L. acidophilus LAI demonstrated, in general, a lower resistance to the yoghurt environment than B. bifidum BBI. On the other hand, the full-fat yoghurt was a more inhibitory medium than the reduced-fat one, especially for B. bifidum BBI. Regarding the lactic starters used, the results showed that the culture SISD was clearly more inhibitory for both probiotic organisms than the culture SID. The loss of cell viability in yoghurt samples was different (higher in some cases and lower in others) from that due to lactic acid only. In general, pH values of 4.5 or lower jeopardised the cell viability of the probiotic organisms in yoghurt stored at 5°C. This work shows the importance of selecting a suitable combination of probiotic strains and starter cultures when different yoghurt types are formulated.     

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.     

Probiotic yoghurt functionalised with microalgae and Zedo gum: chemical,microbiological, rheological and sensory characteristics

In this study, using a central composite design, the effects of addition of Spirulina platensis and Zedo gum to plain and probiotic yoghurt samples were investigated during storage. Lactobacillus paracasei proliferation was directly dependent on the addition of microalgae and was inversely affected by storage time. Probiotic samples containing S. platensis showed the highest antioxidative activity. Maximum stability was obtained at higher amounts of Zedo gum, while organoleptic and rheological attributes improved at 0.25% Zedo gum. Given the importance of probiotic viability, supplementation of probiotic yoghurt with Zedo gum/S. platensis may be consideredas a novel nutraceutical formulation.     

Optimisation of probiotic yoghurt production enriched with phytosterols

To optimise the formulation of phytosterol‐enriched probiotic yoghurt, the effect of different concentrations of phytosterols, fat and the probiotic inoculation rate on the survival of Lactobacillus acidophilus LA‐5, Bifidobacterium lactis BB‐12 and physicochemical indices over 14 days of storage was explored. Data analysis showed that the phytosterol concentration and fat content were two crucial factors affecting probiotic viability. Addition of phytosterols had no adverse effect on the overall scores for sensory attributes. Regarding maximisation of viability and storage time, the optimum conditions were found to be fat = 8.07% (w/v), phytosterol = 18 g/L, probiotic inoculation rate = 71.42 mg/L and storage time = 12 days.     

Development of rice as potential carriers for probiotic Lactobacillus amylovorus

An experiment using a standard strain of Lactobacillus amylovorus TISTR1110 to test for the capability of carbohydrate utilisation of nine cultivars of rice found that L. amylovorus TISTR1110 could utilise carbohydrate from all cultivars and also exhibit nonhaemolytic properties. After testing the viability of the strain under simulated gastrointestinal tract conditions by enumeration after 5 h, the results showed that the amount of L. amylovorus TISTR1110 present was 4.0 × 10⁵ CFU/mL or a 73.78% survival rate. From the evaluation of Thai rice cultivars as carriers in probiotic products, the highest amount of probiotic bacteria was found in baked and encapsulated glutinous Luem Pua Thai sticky rice up to 4.9 × 10⁶ CFU/g or a survival rate of 69.39 ± 0.06%. The second highest rate (4.8 × 10⁵ CFU/g) was found in heat–moisture steamed rice of Riceberry rice cultivar or a survival rate of 59.74 ± 0.11%. After testing the capability of adherence using SEM, the results showed that glutinous Luem Pua sticky rice resulted in considerably high survival rate of probiotic bacteria compared with other rice. Additionally, the microbiological safety test reported that the amounts of contaminants were acceptable.     

Comparison of vacuum impregnation and soaking techniques for addition of the probiotic Lactobacillus acidophilus to minimally processed melon

This study aimed to evaluate the vacuum impregnation (VI) and soaking methods in the addition of Lactobacillus acidophilusLA‐3 to minimally processed melon (MPM). The melons were washed, sanitised in chlorine solution (200 mg L^?1), peeled and cutted into cubes. Lactobacillus acidophilusLA‐3 (1.4 × 10¹⁰ CFU g^?1) were added to the MPM through both techniques. The L. acidophilusLA‐3 count in MPM was similar to those commonly found in dairy products having probiotic claim, but VI was more efficient than soaking in maintaining the viability (8.61 and 7.98 Log CFU g^?1, respectively). The pH, acidity and soluble solids were not affected by probiotic culture and the incorporation technique; however, the VI affected the firmness of fruit. The MPM was within Brazilian standards for their microbiological characteristics. MPM may be used as a carrier of probiotic bacteria, being one more alternative for individuals who consume probiotic products.     

Physical properties and microstructure of yoghurts supplemented with milk protein hydrolysates

The physical properties and the microstructure of yoghurts containing probiotic bacteria, and supplemented with milk protein hydrolysates, were studied. Three casein hydrolysates and three whey protein hydrolysates were added to milk at a concentration ranging from 0.25 to 4 g L⁻¹. The milks were then fermented with either of two different cultures. The resulting yoghurts with added hydrolysates were compared to the control yoghurt without supplementation. For both cultures, addition of hydrolysates decreased the complex viscosity and graininess in yoghurts. The addition of hydrolysates also reduced fermentation time. Microstructural observations showed a more open and less branched structure in yoghurts when milk protein hydrolysates were incorporated. The difference in fermentation time between milks with different levels of added hydrolysates could partially explain the differences in microstructure and physical properties of the final yoghurts.     

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.     

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.