Bifidobacterium Bb-12 microencapsulated by spray drying with whey: Survival under simulated gastrointestinal conditions,tolerance to NaCl,and viability during storage

Bifidobacterium Bb-12 was microencapsulated by spray drying with whey. This present work investigated the survival of these microcapsules under simulated gastrointestinal conditions, as well as their tolerance to NaCl and their viability during storage. The results showed a small decrease in the viability of microencapsulated Bifidobacterium at low pH. In relation to the exposure of Bifidobacterium to bile, microencapsulation with whey did not protect the probiotic cells; however, the viability of the microcapsules remained >6 log cfu/g, even after 24 h of incubation at the highest bile concentration analyzed. No growth was noted with either the free cells or the microencapsulated cells on MRS-LP with NaCl. The viability of the microcapsules stored at 4 °C remained high and constant for 12 weeks. When the microcapsules were added to a dairy dessert, the probiotic count remained above 7 log cfu/g for 6 weeks. Therefore, whey is a promising encapsulating agent for Bifidobacterium Bb-12.     

Impact of inulin and okara on Lactobacillus acidophilus La-5 and Bifidobacterium animalis Bb-12 viability in a fermented soy product and probiotic survival under in vitro simulated gastrointestinal conditions

The effect of inulin and/or okara flour on Lactobacillus acidophilus La-5 and Bifidobacterium animalis Bb-12 viability in a fermented soy product (FSP) and on probiotic survival under in vitro simulated gastrointestinal conditions were investigated throughout 28 days of storage at 4 °C. Employing a 2² design, four FSP trials were produced from soymilk fermented with ABT-4 culture (La-5, Bb-12, and Streptococcus thermophilus): FSP (control); FSP-I (with inulin, 3 g/100 mL of soymilk); FSP-O (with okara, 5 g/100 mL); FSP-IO (with inulin + okara, ratio 3:5 g/100 mL). Probiotic viabilities ranged from 8 to 9 log cfu/g during the 28 days of storage, and inulin and/or okara flour did not affect the viability of La-5 and Bb-12. Bb-12 resistance to the artificial gastrointestinal juices was higher than for La-5, since the Bb-12 and La-5 populations decreased approximately 0.6 log cfu/g and 3.8 log cfu/g, respectively, throughout storage period. Even though the protective effect of inulin and/or okara flour on probiotic microorganisms was not significant, when compared to a fresh culture, the FSP matrix improved Bb-12 survival on day 1 of storage and may be considered a good vehicle for Bb-12 and could play an important role in probiotic protection against gastrointestinal juices.     

Viability of Lactobacillus acidophilus La-5 added solely or in co-culture with a yoghurt starter culture and implications on physico-chemical and related properties of Minas fresh cheese during storage

The effect of a probiotic culture of Lactobacillus acidophilus (La-5), added solely or in co-culture with a starter culture of Streptococcus thermophilus, on texture, proteolysis and related properties of Minas fresh cheese during storage at 5 °C was investigated. Three cheese-making trials were prepared and produced with no addition of cultures (T1 - control), supplemented with La-5 (T2), and with La-5 + S. thermophilus (T3). Viable counts of La-5 remained above 6.00 log cfu g⁻¹ during the whole storage for T2, reaching 7.00 log cfu g⁻¹ on the 14th day. For T3, the counts of La-5 remained above 6.00 log cfu g⁻¹ after 7 days of storage. Due to the presence of S. thermophilus, T3 presented the highest proteolytic index increase and titratable acidity values. Nevertheless, these results and S. thermophilus addition had no influence on viability of La-5 which presented satisfactory populations for a probiotic food. Moreover, the use of a yoghurt culture for the production of Minas fresh cheese T3 supplemented with La-5 resulted in a good quality product, with a small rate of post-acidification, indicating that traditional yoghurt culture could be employed in co-culture with La-5 to improve the quality of this cheese.     

Survival of Lactobacillus acidophilus and Bifidobacterium animalis ssp. lactis in stirred fruit yogurts

The effect of commercial fruit preparations (mango, mixed berry, passion fruit and strawberry) on the viability of probiotic bacteria, Lactobacillus acidophilus LAFTI^® L10 and Bifidobacterium animalis ssp. lactis LAFTI^® B94 in stirred yogurts during storage (35 days) at refrigerated temperature (4 °C) was evaluated. The results showed that addition of either 5 or 10 g/100 g fruit preparations had no significant (p>0.05) effect on the viability of the two probiotic strains except on L. acidophilus LAFTI L10 yogurt with 10 g/100 g passion fruit or mixed berry. After the addition of fruit preparation, 96% of the yogurts incorporated with fruit preparation did not exhibit a greater loss in the viability of probiotic bacteria compared to plain yogurt during the storage period. A correlation between the post-storage pH in yogurts and the survival of probiotic bacteria was observed. All the yogurts, however, contained the recommended levels of (10⁶-10⁷ cfu/g) probiotic bacteria at the end of 35-day shelf life.     

Tropical fruit pulps decreased probiotic survival to in vitro gastrointestinal stress in synbiotic soy yoghurt with okara during storage

The effect of mango and guava pulps on Lactobacillus acidophilus La-5 and Bifidobacterium animalis Bb-12 viability in a soy yoghurt (SY) and on probiotic survival under simulated gastrointestinal conditions were investigated throughout 28 days of storage at 4 °C. The impact of fruit pulps on SY sensory acceptability was also assessed. Three formulations were produced from soymilk fermented with ABT-4 culture (La-5, Bb-12, and Streptococcus thermophilus) and supplemented with inulin and okara: SYC (control), SYM (with mango pulp), and SYG (with guava pulp). All formulations showed probiotic viabilities ranging from 8 to 9 log cfu/g, and fruit pulps did not affect the probiotic viabilities. However, the fruit pulps decreased probiotic survival significantly to simulated gastrointestinal stress. Acceptability was higher for SYM and this difference was significant at 21 days. Therefore, the improved acceptability of SY through the addition of fruit pulps might lead to a reduction in probiotic functionality.     

Effect of calcium alginate and resistant starch microencapsulation on the survival rate of Lactobacillus acidophilus La5 and sensory properties in Iranian white brined cheese

Two types of probiotic cheese, with free and microencapsulated bacteria, were manufactured in triplicate under the same conditions. The number of viable cells during 182 days of storage in refrigerated conditions was evaluated. The number of viable cells of Lactobacillus acidophilus was reduced significantly from day 28 to day 182 of storage period in both types of cheese, but reduction in the cheese containing free cells (5.1 ± 0.67 log cfu g⁻¹) was significantly p < 0.05 higher than the cheese containing microencapsulated cells (11.00 ± 0.58 log cfu g⁻¹). The results showed that, microencapsulation in calcium alginate gel and resistant starch was able to increase the survival rate of L. acidophilus La5 in Iranian white brined cheese after 6 months of storage.     

Studies on the retention of microencapsulated l-5-methyltetrahydrofolic acid in baked bread using skim milk powder

Our aim was to protect l-5-methyltetrahydrofolic acid (L-5-MTHF) from degradation throughout the baking and storage of a fortified white bread using microencapsulation. L-5-MTHF, with or without sodium ascorbate (ASC), was microencapsulated using skim milk powder (SMP) as the coating agent. Recoveries of L-5-MTHF in spray-dried materials were greater than 95 ± 5%. Microencapsulated L-5-MTHF was completely released from the skim milk coating material in simulated gastric fluid within the first 10 min at 37 °C. Incorporation of SMP-L-5-MTHF or SMP-L-5-MTHF + ASC into bread gave recoveries of 81.3 ± 1.3% and 87.1 ± 1.2% (n = 3), respectively, for L-5-MTHF immediately after bread baking. These treatments also showed significantly (p < 0.05) greater L-5-MTHF stability during room temperature storage, compared to the free L-5-MTHF. This study has shown that SMP is an effective microencapsulating agent and in the presence of ASC will produce excellent conditions for stabilising L-5-MTHF in baked bread.     

Effects of refrigeration,freezing and replacement of milk fat by inulin and whey protein concentrate on texture profile and sensory acceptance of synbiotic guava mousses

The effects of refrigeration, freezing and substitution of milk fat by inulin and whey protein concentrate (WPC) on the texture and sensory features of synbiotic guava mousses supplemented with the probiotic, Lactobacillus acidophilus La-5, and the prebiotic fibre oligofructose, were studied. The frozen storage (−18 ± 1 °C), followed by thawing at 4 °C before the analyses, and the complete replacement of the milk fat by inulin plus WPC, led to significant differences in the instrumental texture parameters of mousses (P < 0.05). Nonetheless, these changes did not affect the sensory acceptability of the products studied. The frozen storage may be employed to extend the shelf-life of synbiotic guava mousses. Additionally, to obtain a texture profile similar to the traditional product, the simultaneous addition of inulin and WPC is recommended only for the partial replacement of milk fat in refrigerated and frozen mousses, and the total proportion of both ingredients together should not exceed 2.6%.     

Bactericidal activity of lauric arginate in milk and Queso Fresco cheese against Listeria monocytogenes cold growth

Lauric arginate (LAE) at concentrations of 200 ppm and 800 ppm was evaluated for its effectiveness in reducing cold growth of Listeria monocytogenes in whole milk, skim milk, and Queso Fresco cheese (QFC) at 4°C for 15 to 28 d. Use of 200 ppm of LAE reduced 4 log cfu/mL of L. monocytogenes to a nondetectable level within 30 min at 4°C in tryptic soy broth. In contrast, when 4 log cfu/mL of L. monocytogenes was inoculated in whole milk or skim milk, the reduction of L. monocytogenes was approximately 1 log cfu/mL after 24 h with 200 ppm of LAE. When 800 ppm of LAE was added to whole or skim milk, the initial 4 log cfu/mL of L. monocytogenes was nondetectable following 24 h, and no growth of L. monocytogenes was observed for 15 d at 4°C. With surface treatment of 200 or 800 ppm of LAE on vacuum-packaged QFC, the reductions of L. monocytogenes within 24 h at 4°C were 1.2 and 3.0 log cfu/g, respectively. In addition, the overall growth of L. monocytogenes in QFC was decreased by 0.3 to 2.6 and by 2.3 to 5.0 log cfu/g with 200 and 800 ppm of LAE, respectively, compared with untreated controls over 28 d at 4°C. Sensory tests revealed that consumers could not determine a difference between QFC samples that were treated with 0 and 200 ppm of LAE, the FDA-approved level of LAE use in foods. In addition, no differences existed between treatments with respect to flavor, texture, and overall acceptability of the QFC. Lauric arginate shows promise for potential use in QFC because it exerts initial bactericidal activity against L. monocytogenes at 4°C without affecting sensory quality.     

A probiotic soy-based innovative product as an alternative to petit-suisse cheese

The present study aimed to develop a probiotic soy-based product similar to petit-suisse cheese and to evaluate its perspectives regarding potential for consumer health benefits, sensory acceptability, and instrumental texture during storage. Three different trials were studied: MP (milk-based petit-suisse – control); MSP (mixed product with milk cream and soy); SP (soymilk-based product). The formulations were produced with an ABT culture, containing Lactobacillus acidophilus La-5, Bifidobacterium animalis Bb-12, and the starter Streptococcus thermophilus and stored at 4 °C for up to 28 days. Bb-12 viability remained always above 8 log cfu g⁻¹ for all trials, whereas viability of La-5 was satisfactory at the end of storage for MP (7.56 log cfu g⁻¹) and MSP (6.49 log cfu g⁻¹), but only up to 21 days (6.84 log cfu g⁻¹) for SP. The pH remained stable and was lower for MSP (p < 0.05), whereas instrumental hardness and gumminess increased in soy-based products (MSP and SP) and decreased in the control (MP). SP had the highest sensory score means (6.4) on day 21, being sensorially attractive to provide consumers with a functional food without dairy ingredients and with high viability of the probiotic microorganisms.     

Survival and sensory acceptability of probiotic microorganisms in a nonfermented frozen vegetarian dessert

Probiotic microorganisms were incorporated into a nonfermented, vegetarian frozen soy dessert at initial populations greater than 10⁶ cfu/g. The product was assessed for the survival of probiotic microorganisms and sensory acceptability. Lactobacillus acidophilus MJLA1, L. rhamnosus 100-C, L. paracasei ssp. paracasei 01, Bifidobacterium lactis BBDB2, B. lactis BB-12 all survived the 6 month storage trial at populations of 10⁷ cfu/g or greater. Saccharomyces boulardii 74012 did not retain sufficient viability, decreasing below the desirable level of 10⁶ cfu/g. To detect sensory differences, product containing L. acidophilus MJLA1, S. boulardii 74012 and an uninoculated control were stored for 0, 4 and 7 months and compared using triangle tests. Product inoculated with L. acidophilus MJLA1 could not be distinguished from the control sample. Product with S. boulardii 74012 differed from the control and L. acidophilus MJLA1 and developed undesirable flavours during storage. The frozen soy dessert was a suitable food for the delivery of bacterial probiotic strains with excellent viability and acceptable sensory characteristics.     

Probiotic viability and storage stability of yogurts and fermented milks prepared with several mixtures of lactic acid bacteria

Currently, the food industry wants to expand the range of probiotic yogurts but each probiotic bacteria offers different and specific health benefits. Little information exists on the influence of probiotic strains on physicochemical properties and sensory characteristics of yogurts and fermented milks. Six probiotic yogurts or fermented milks and 1 control yogurt were prepared, and we evaluated several physicochemical properties (pH, titratable acidity, texture, color, and syneresis), microbial viability of starter cultures (Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus) and probiotics (Lactobacillus acidophilus, Lactobacillus casei, and Lactobacillus reuteri) during fermentation and storage (35 d at 5°C), as well as sensory preference among them. Decreases in pH (0.17 to 0.50 units) and increases in titratable acidity (0.09 to 0.29%) were observed during storage. Only the yogurt with S. thermophilus, L. delbrueckii ssp. bulgaricus, and L. reuteri differed in firmness. No differences in adhesiveness were determined among the tested yogurts, fermented milks, and the control. Syneresis was in the range of 45 to 58%. No changes in color during storage were observed and no color differences were detected among the evaluated fermented milk products. Counts of S. thermophilus decreased from 1.8 to 3.5 log during storage. Counts of L. delbrueckii ssp. bulgaricus also decreased in probiotic yogurts and varied from 30 to 50% of initial population. Probiotic bacteria also lost viability throughout storage, although the 3 probiotic fermented milks maintained counts ≥10⁷ cfu/mL for 3 wk. Probiotic bacteria had variable viability in yogurts, maintaining counts of L. acidophilus ≥10⁷ cfu/mL for 35 d, of L. casei for 7 d, and of L. reuteri for 14 d. We found no significant sensory preference among the 6 probiotic yogurts and fermented milks or the control. However, the yogurt and fermented milk made with L. casei were better accepted. This study presents relevant information on physicochemical, sensory, and microbial properties of probiotic yogurts and fermented milks, which could guide the dairy industry in developing new probiotic products.     

Short communication: Incorporation of inulin and transglutaminase in fermented goat milk containing probiotic bacteria

Goat milk is a good carrier for probiotic bacteria; however, it is difficult to produce fermented goat milk with a consistency comparable to that of fermented cow milks. It can be improved by the addition of functional stabilizers, such as inulin, or treatment with transglutaminase. The aim of this study was to determine the effect of cold storage of inulin and microbial transglutaminase on the viability of Lactobacillus acidophilus La-5 and Bifidobacterium animalis ssp. lactis Bb-12 in fermented goat milk. Microbiological analysis included the determination of the probiotic bacteria cell count in fermented milk samples, whereas physico-chemical analysis included the analysis of fat content, titratable acidity, and pH of raw, pasteurized, and fermented goat milk samples. No positive influence of inulin or microbial transglutaminase on the viability of probiotics in fermented goat's milk samples was observed. Nevertheless, the population of probiotics remained above 6 log cfu/g after 8 wk of storage at 5°C.     

Effect of inulin polymerization degree on various properties of synbiotic fermented milk including Lactobacillus acidophilus La-5 and Bifidobacterium animalis Bb-12

The effects of inulin degree of polymerization (DP) on the viabilities of Lactobacillus acidophilus La-5 and Bifidobacterium animalis Bb-12 and on some parameters of fermented milk, such as microbiological, rheological, biochemical, and sensory properties, were investigated during 30 d of storage. Samples were produced using L. acidophilus La-5 and B. animalis Bb-12, along with inulin having different DP as prebiotic, and the effects of high-DP (DP ≥ 23) and low-DP (DP ≤ 10) inulin on fermented milk, were determined. The viability of both strains increased when they were used with inulin having any DP. The addition of inulin increased the consistency index of all samples. During storage, we observed an increase in lactic and acetic acid contents of samples in which high-DP inulin was used, for both strains of bacteria. Of the combinations we tested, the sample produced with L. acidophilus La-5 and high-DP inulin demonstrated the highest rheological and sensory performance as well as the best viability of probiotics.     

Influence of addition of raffinose family oligosaccharides on probiotic survival in fermented milk during refrigerated storage

The influence of the addition of raffinose family oligosaccharides (RFOs) extracted from lupin seeds on the survival of Bifidobacterium lactis Bb-12 and Lactobacillus acidophilus La-5 in fermented milk during 21 days of storage in refrigerated conditions was studied. For this purpose, viability and metabolic activity (expressed as pH, lactic and acetic acid production and utilization of soluble carbohydrates) of probiotic bacteria were determined. Retention of viability of B. lactis Bb-12 and L. acidophilus La-5 was greater in fermented milk with RFOs. The pH of probiotic fermented milk at 21 days of storage was lower (4.27) compared with probiotic fermented milk with RFOs (4.37). The highest levels of lactic and acetic acid were produced in probiotic fermented milk without RFOs compared with probiotic fermented milk with RFOs during storage at 4 °C. Soluble carbohydrates were utilised in fermented milk with and without RFOs, respectively, for maintaining B. lactis Bb-12 and L. acidophilus populations during refrigerated storage. In conclusion, all these experiments provide convincing evidence that RFOs have beneficial effects on the survival of these probiotic cultures in dairy products. As a result, such stored dairy products containing both probiotics and prebiotics have synergistic actions in the promotion of health.     

An excessively high Lactobacillus acidophilus inoculation level in yogurt lowers product quality during storage

The effect of manufacturing yogurt with a wide variation in Lactobacillus acidophilus inoculation level while holding the yogurt culture inoculation level constant on the properties of the resulting yogurt was determined to find out if any problems can occur if an excessively high level of L. acidophilus is used in yogurt production. Four batches of plain, set-style yogurt were manufactured with skim milk, nonfat dry milk, yogurt cultures, and with or without L. acidophilus (0, 0.0239, 0.238, or 2.33 g/100 g). After homogenization, pasteurization, and cooling, yogurt mixes were inoculated, poured into containers, incubated to pH 4.5, and cooled. Lactobacilli and L. acidophilus counts, pH, amount of syneresis, color, apparent viscosities, and sensory scores were determined during storage. The yogurt inoculated with 0.238 g/100 g L. acidophilus had the highest L. acidophilus counts from 4 to 7 wk. Yogurts inoculated with 2.33 g/100 g L. acidophilus generally had lower lactobacilli counts, L* values, apparent viscosities, and sensory scores but more syneresis and higher a* and b* values than the remaining yogurts. An excessively high inoculated level of L. acidophilus (2.33 g/100 g) resulted in an inferior quality yogurt.     

Evaluation of culture media for enumeration of Lactobacillus acidophilus, Lactobacillus casei and Bifidobacterium animalis in the presence of Lactobacillus delbrueckii subsp bulgaricus and Streptococcus thermophilus

The study compared the growth capability of probiotic (Lactobacillus acidophilus La05, Lactobacillus casei Lc01 and Bifidobacterium animalis Bb12) and non-probiotic (Lactobacillus delbrueckii subsp bulgaricus and Streptococcus thermophilus) cultures on twenty-one culture media grouped according to selectivity: non-selective agars, selective agars without antibiotics and MRS agars containing different combinations of lithium chloride, cystein, bile salts and antibiotics. Four of these media were selected for quantitative enumeration of L. acidophilus La05, L. casei Lc01, and B. animalis Bb12. The best culture media and incubation conditions for enumeration of the probiotic cultures were: B. animalis: MRS agar with dicloxacillin, 37 °C or 42 °C, anaerobiosis; L. acidophilus: MRS agar with bile salts, 37 °C or 42 °C, aerobiosis; L. casei: MRS agar with lithium chloride and sodium propionate, 37 °C or 42 °C, aerobiosis or anaerobiosis. Plating on MRS with glucose replaced by maltose, 37 °C or 42 °C, anaerobiosis, will distinguish probiotic from non-probiotic cultures. For enumeration of each probiotic in a mixed culture, the following media and incubation conditions were recommended: B. animalis: 4ABC-MRS, 42 °C, anaerobiosis, L. acidophilus: LC medium, 42 °C, aerobiosis or anaerobiosis and L. casei: LP-MRS, 42 °C, aerobiosis or anaerobiosis. In all experiments, differences in counts using pour plating or surface plating were not significant (P ≤ 0.05).     

Fate of Staphylococcus aureus in cheese treated by ultrahigh pressure homogenization and high hydrostatic pressure

We evaluated the influence of ultrahigh pressure homogenization (UHPH) treatment applied to milk containing Staphylococcus aureus CECT 976 before cheese making, and the benefit of applying a further high hydrostatic pressure (HHP) treatment to cheese. The evolution of Staph. aureus counts during 30 d of storage at 8°C and the formation of staphylococcal enterotoxins were also assessed. Milk containing approximately 7.3 log₁₀ cfu/mL of Staph. aureus was pressurized using a 2-valve UHPH machine, applying 330 and 30 MPa at the primary and the secondary homogenizing valves, respectively. Milk inlet temperatures (T_in) of 6 and 20°C were assayed. Milk was used to elaborate soft-curd cheeses (UHPH cheese), some of which were additionally submitted to 10-min HHP treatments of 400 MPa at 20°C (UHPH+HHP cheese). Counts of Staph. aureus were measured on d 1 (24 h after manufacture or immediately after HHP treatment) and after 2, 15, and 30 d of ripening at 8°C. Counts of control cheeses not pressure-treated were approximately 8.5 log₁₀ cfu/g showing no significant decreases during storage. In cheeses made from UHPH treated milk at T_in of 6°C, counts of Staph. aureus were 5.0 ± 0.3 log₁₀ cfu/g at d 1; they decreased significantly to 2.8 ± 0.2 log₁₀ cfu/g on d 15, and were below the detection limit (1 log₁₀ cfu/g) after 30 d of storage. The use of an additional HHP treatment had a synergistic effect, increasing reductions up to 7.0 ± 0.3 log₁₀ cfu/g from d 1. However, for both UHPH and UHPH+HHP cheeses in the 6°C T_in samples, viable Staph. aureus cells were still recovered. For samples of the 20°C T_in group, complete inactivation of Staph. aureus was reached after 15 d of storage for both UHPH and UHPH+HHP cheese. Staphylococcal enterotoxins were found in controls but not in UHPH or UHPH+HHP treated samples. This study shows a new approach for significantly improving cheese safety by means of using UHPH or its combination with HHP.     

Survival of probiotics encapsulated in chitosan-coated alginate beads in yoghurt from UHT- and conventionally treated milk during storage

Survival of the microencapsulated probiotics, Lactobacillus acidophilus 547, Bifidobacterium bifidum ATCC 1994, and Lactobacillus casei 01, in stirred yoghurt from UHT- and conventionally treated milk during low temperature storage was investigated. The probiotic cells both as free cells and microencapsulated cells (in alginate beads coated with chitosan) were added into 20 g/100 g total solids stirred yoghurt from UHT-treated milk and 16 g/100 g total solids yoghurt from conventionally treated milk after 3.5 h of fermentation. The products were kept at 4 °C for 4 weeks. The survival of encapsulated probiotic bacteria was higher than free cells by approximately 1 log cycle. The number of probiotic bacteria was maintained above the recommended therapeutic minimum (10⁷ cfu g⁻¹) throughout the storage except for B. bifidum. The viabilities of probiotic bacteria in yoghurts from both UHT- and conventionally treated milks were not significantly (P>0.05) different.     

Effect of high-pressure processing on reduction of Listeria monocytogenes in packaged Queso Fresco

The effect of high-hydrostatic-pressure processing (HPP) on the survival of a 5-strain rifampicin-resistant cocktail of Listeria monocytogenes in Queso Fresco (QF) was evaluated as a postpackaging intervention. Queso Fresco was made using pasteurized, homogenized milk, and was starter-free and not pressed. In phase 1, QF slices (12.7 × 7.6 × 1 cm), weighing from 52 to 66 g, were surface inoculated with L. monocytogenes (ca. 5.0 log₁₀ cfu/g) and individually double vacuum packaged. The slices were then warmed to either 20 or 40°C and HPP treated at 200, 400, and 600 MPa for hold times of 5, 10, 15, or 20 min. Treatment at 600 MPa was most effective in reducing L. monocytogenes to below the detection level of 0.91 log₁₀ cfu/g at all hold times and temperatures. High-hydrostatic-pressure processing at 40°C, 400 MPa, and hold time ≥15 min was effective but resulted in wheying-off and textural changes. In phase 2, L. monocytogenes was inoculated either on the slices (ca. 5.0 log₁₀ cfu/g; ON) or in the curds (ca. 7.0 log₁₀ cfu/g; IN) before the cheese block was formed and sliced. The slices were treated at 20°C and 600 MPa at hold times of 3, 10, and 20 min, and then stored at 4 and 10°C for 60 d. For both treatments, L. monocytogenes became less resistant to pressure as hold time increased, with greater percentages of injured cells at 3 and 10 min than at 20 min, at which the lethality of the process increased. For the IN treatment, with hold times of 3 and 10 min, growth of L. monocytogenes increased the first week of storage, but was delayed for 1 wk, with a hold time of 20 min. Longer lag times in growth of L. monocytogenes during storage at 4°C were observed for the ON treatment at hold times of 10 and 20 min, indicating that the IN treatment may have provided a more protective environment with less injury to the cells than the ON treatment. Similarly, HPP treatment for 10 min followed by storage at 4°C was the best method for suppressing the growth of the endogenous microflora with bacterial counts remaining below the level of detection for 2 out of the 3 QF samples for up to 84 d. Lag times in growth were not observed during storage of QF at 10°C. Although HPP reduced L. monocytogenes immediately after processing, a second preservation technique is necessary to control growth of L. monocytogenes during cold storage. However, the results also showed that HPP would be effective for slowing the growth of microorganisms that can shorten the shelf life of QF.