共查询到20条相似文献,搜索用时 31 毫秒
1.
《Food microbiology》2004,21(3):343-349
One hundred and fifty-eight strains of lactic acid bacteria isolated from Algerian raw goat's milk were identified and technologically characterized. Five genera were found: Lactobacillus (50.63%), Lactococcus (25.94%), Streptococcus (14.56%), Leuconostoc (7.59%) and Pediococcus (1.26%). The predominant species were Lactococcus lactis (32 strains), Streptococcus thermophilus (23 strains), Lactobacillus bulgaricus (19 strains), Lb. helveticus (16 strains) and Lb. plantarum (14 strains).Approximately 39% of the lactic acid bacteria isolated produced more than 0.6% lactic acid (w/v) after 18 h of incubation, and belonged to the Lactococcus and Lactobacillus genera. The highest proteolytic activity was approximately 3 mg tyrosine l−1 for mesophilic strains and nearly 5 mg tyrosine l−1 for thermophilic lactobacilli after 72 h. High aromatic activity (more than 0.8 mg diacetyl l−1 after 16 h) was detected in 14% of the strains.Nine strains were used to make dairy products (a yoghurt-like product and Edam-type cheese) on a pilot scale in the laboratory. The best-liked organoleptic characteristics were noted in a yoghurt produced with a mixed culture made up of S. thermophilus (strain 16TMC+) and Lb. helveticus (strain 20TMC) and in a cheese made with a starter composed of Lc. lactis subsp. lactis (strain 10MCM) and L. lactis subsp. lactis (V.P. +) (strain 19MCM). 相似文献
2.
《International Dairy Journal》2006,16(10):1181-1189
The viability of Lactobacillus acidophilus LAFTI® L10, Bifidobacterium lactis LAFTI® B94, and L. paracasei LAFTI® L26 and their proteolytic activities were assessed in yoghurt at different termination pH of 4.45, 4.50, 4.55, and 4.60 in the presence of L. delbrueckii ssp. bulgaricus Lb1466 and Streptococcus thermophilus St1342 during 28 days of storage at 4 °C. All strains achieved the recommended level of 6.00 log cfu g−1 of the product with L. acidophilus LAFTI® L10 and L. paracasei LAFTI® L26 exceeding the number to 8.00 and 7.00 log cfu g−1, respectively. Lactobacilli strains showed a good cellular stability maintaining constant concentration throughout storage period regardless of termination pH. On the other hand, the cell counts of B. lactis LAFTI® B94 decreased by one log cycle at the end of storage. The presence of probiotic organisms enhanced proteolysis significantly in comparison with the control batch containing L. delbrueckii ssp. bulgaricus Lb1466 and S. thermophilus St1342 only. The proteolytic activity varied due to termination pH, but also appeared to be strain related. The increased proteolysis improved survival of L. delbrueckii ssp. bulgaricus Lb1466 during storage resulting in lowering of pH and production of higher levels of organic acids, which might have caused the low cell counts for B. lactis LAFTI® B94. 相似文献
3.
《International Dairy Journal》2006,16(4):324-334
The objective of this work was to study the autolytic behaviour of strains of mesophilic (Lactococcus lactis subsp. lactis and L. lactis subsp. cremoris) and thermophilic lactic acid bacteria (Lactobacillus helveticus, Lb. delbrueckii subsp. lactis and Streptococcus thermophilus) in UF cheese. Cheeses were made from a UF-retentate (milk concentrated by a factor of 6) of microfiltered milk (0.8 μm pore size membrane) using the following starter systems: (1) single inocula of autolytic strains of L. lactis (US3, AM2 or AM1), non-autolytic strains of L. lactis (AM2-C or CNRZ-144), (2) a co-inocula of strains of Lb. helveticus (ITG-LH1, CNRZ-32 or CNRZ-303), Lb. delbrueckii subsp. lactis (ITG-LL14 or ITG-LL51) with the same strain of S. thermophilus CNRZ-1358. Cell viability was monitored over a 28 day ripening period by enumeration on selective media. Degree of lysis was determined by the measurement of the intracellular marker lactate dehydrogenase (LDH) activity, and also by immunodetection of intracellular proteins with species specific antibodies. In UF cheeses, lysis of autolytic strains of L. lactis was significantly delayed, showing release of intracellular components after 21 days of ripening. No lysis was observed for non-autolytic L. lactis strains or for S. thermophilus. Lysis of thermophilic lactobacilli (Lb. helveticus, Lb. delbrueckii), was observed from the start of ripening, but the onset and the level of lysis observed was strain and species dependent. 相似文献
4.
《International Dairy Journal》2002,12(6):511-523
A microbiological, compositional, biochemical and textural characterisation of the pasta filata Caciocavallo Pugliese cheese during ripening is reported. Fully ripened cheese contained a total of ca. log 8.0 cfu g−1 mesophilic bacteria and ca. log 6.0 cfu g−1 presumptive staphylococci, while the number of thermophilic and mesophilic rod and coccus lactic acid bacteria varied during ripening. A two-step RAPD-PCR protocol was used to differentiate biotypes. The natural whey starter was composed mainly of Lactobacillus delbrueckii, Lb. fermentum, Lb. gasseri, Lb. helveticus and Streptococcus thermophilus strains. After day 1 of ripening, Lb. delbrueckii became dominant and some strains of Enterococcus durans and E. faecalis appeared. Non-starter lactic acid bacteria, such as Lb. parabuchneri and Lb. paracasei subsp. paracasei formed a large part of the lactic microflora at 42 and 60 d of ripening. The level of pH 4.6-soluble nitrogen increased from the outer to the inner of the cheese and also increased in each section as ripening progressed, attaining values of 18–15%. Urea-PAGE electrophoresis showed that degradation of αs1-casein was more rapid than that of β-casein throughout ripening and the rates at which both caseins were degraded greatly increased from the outside to the inside of the cheese. Based on the primary proteolysis products, both chymosin and plasmin appeared to be active. RP-HPLC profiles of the 70% ethanol-soluble, pH 4.6-soluble nitrogen, showed a large number of peaks, indicating a heterogeneous mixture of proteolytic products. There were both age- and section-related changes in the area of the different peptide peaks. Butyric (C4:0), caproic (C6:0), palmitic (C16:0) and oleic (C18:1) acids were the free fatty acids found at the highest concentrations. The level of short chain fatty acids (e.g., butyric and caproic) decreased from the middle and inner to outer sections of the cheese. Peptidase activity in the curd was pronounced, increased during ripening and varied with the cheese section. The greatest increase of the peptidase activity coincided with a change in the lactic microflora and with the prevalence of non-starter lactic acid bacteria. Microbial esterases were supposed to be active together with rennet paste. Little change in the firmness and fractures stress during maturation were found by textural analyses of the raw cheese. The flowability was similar to that of typical low-moisture Mozzarella cheese, while stretchability was lower. The heat-induced changes in phase angle of Caciocavallo Pugliese cheese indicated a phase transition from largely elastic rheological characteristics in unheated cheese to a more viscous and fluid character in melted cheese. 相似文献
5.
《International Dairy Journal》2003,13(9):743-753
The effect of two commercially available adjunct cultures, LBC 80 (Lactobacillus casei subsp. rhamnosus) and CR-213 (containing Lactococcus lactis subsp. cremoris and Lc. lactis subsp. lactis) on the proteolysis in low-fat hard ewes’ milk cheese of Kefalograviera-type was investigated. Two controls, a full-fat cheese (306 g kg−1 fat, 378 g kg−1 moisture) and a low-fat cheese (97 g kg−1 fat, 486 g kg−1 moisture, made using a modified procedure), were also prepared. The effect of adjunct culture on proteolysis, as examined by polyacrylamide gel electrophoresis of cheese and water soluble cheese extracts, was marginal. The reverse-phase HPLC peptide profiles of the water soluble extracts from low-fat cheeses were similar although some quantitative differences were observed between low-fat control cheese and experimental cheeses. The fat content as reflected by the differences in peptide profiles affected the pattern of proteolysis. Proteolysis, as measured by the percentage of total nitrogen soluble in water or in 120 g L−1 trichloroacetic acid, was significantly (P<0.05) affected by the addition of adjunct cultures. Furthermore, the adjunct cultures enhanced the production of low molecular mass nitrogenous compounds; the levels of total nitrogen, soluble in 50 g L−1 phosphotungstic acid, and of free amino acids were significantly (P<0.05) higher in the low-fat experimental cheeses than in the low-fat control cheese. 相似文献
6.
The associative growth of Streptococcus thermophilus 95/2 (St 95/2) and Lactobacillus delbrueckii ssp. bulgaricus 77 (Lb 77) isolated from the Toros mountain region of Turkey was investigated with respect to lactic acid, biomass and β-galactosidase enzyme production using response surface methodology (RSM). The ratio (St 95/2:Lb 77) of the strains and media formulation had significant effect on all responses (p < 0.001). The predicted enzyme activity (2.14 U mL?1), lactic acid (22.50 g L?1) and biomass (7.11 g L?1) production at optimum conditions were very close to the actual experimental values (2.14 U mL?1, 22.94 g L?1 and 7.86 g L?1, respectively). The optimum conditions were to use these cultures in a ratio of 1.66:1.62 (St 95/2:Lb 77) in a medium containing whey (5%), corn steep liquor (4%), potassium phosphate (2%) and peptone (2%) at 43 °C for 8 h. The associative growth provided 6.4% and 39% more β-galactosidase activity and 8.73% and 44% more lactic acid compared with the results obtained using pure St 95/2 and Lb 77 strains, respectively. 相似文献
7.
《International Dairy Journal》2002,12(11):933-938
The inhibitory effect of nisin-producing Lactococcus lactis subsp. lactis UL730 on the growth of enterotoxigenic Staphylococcus aureus J10 during manufacture of Jben, a Moroccan traditional fresh cheese prepared from recombined milk, was investigated.With an inoculum level of 103 cfu mL−1, S. aureus was absent in Jben four days after inoculation when the nisin-producing lactococcus was used as lactic starter. In contrast, it survived after that period, when the starter was non-nisin-producing. No staphylococcal thermonuclease was detected in all Jben samples made from milk inoculated with S. aureus at the level of 103 cfu mL−1.With a higher inoculum of 105 cfu mL−1, S. aureus was still present in Jben after manufacture and persisted during the storage of the product for 3 days in the laboratory, even when the starter used was nisin-producing. Staphylococcal thermonuclease and type C enterotoxin were detected in all Jben samples made from milk inoculated with 105 cfu mL−1. Thermonuclease and enterotoxin were already produced in the coagulum, at 24 h after milk inoculation with S. aureus. 相似文献
8.
《International Dairy Journal》2007,17(9):1083-1088
The effect of barley β-glucan (BG) on the growth of two yogurt starter cultures (SCs) each consisting of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus was investigated. Model yogurt systems were prepared with or without the incorporation of barley BG and lactose to mimic natural levels in milk and allowed to ferment for 8 h at 42 °C. The fermentation efficacy of the SCs was monitored through pH measurements. Samples were collected and analyzed for pH and viscosity at 0, 2, 4, and 8 h. Viscosity was determined using a rotational viscometer at shear rates of 1.29–129 s−1 and 20 °C. The pH measurements indicated no adverse effect on the growth of SCs as the acidification process was consistent with normal pH development, but viscosity measurements suggested that BG was depolymerized by SCs when lactose became a limiting nutrient during fermentation. 相似文献
9.
《International Dairy Journal》2007,17(1):67-78
Cheddar cheeses were produced with starter lactococci and Bifidobacterium longum 1941, B. lactis LAFTI® B94, Lactobacillus casei 279, Lb. paracasei LAFTI® L26, Lb. acidophilus 4962 or Lb. acidophilus LAFTI® L10 to study the survival of the probiotic bacteria and the influence of these organisms on proteolytic patterns and production of organic acid during ripening period of 6 months at 4 °C. All probiotic adjuncts survived the manufacturing process of Cheddar cheese at high levels without alteration to the cheese-making process. After 6 months of ripening, cheeses maintained the level of probiotic organisms at >8.0 log10 cfu g−1 with minimal effect on moisture, fat, protein and salt content. Acetic acid concentration was higher in cheeses with B. longum 1941, B. lactis LAFTI® B94, Lb. casei 279 and Lb. paracasei LAFTI® L26. Each probiotic organism influenced the proteolytic pattern of Cheddar cheese in different ways. Lb. casei 279 and Lb. paracasei LAFTI® L26 showed higher hydrolysis of casein. Higher concentrations of free amino acids (FAAs) were found in all probiotic cheeses. Although Bifidobacterium sp. was found to be weakly proteolytic, cheeses with the addition of those strains had highest concentration of FAAs. These data thus suggested that Lb. acidophilus 4962, Lb. casei 279, B. longum 1941, Lb. acidophilus LAFTI® L10, Lb. paracasei LAFTI® L26 and B. lactis LAFTI® B94 can be applied successfully in Cheddar cheese. 相似文献
10.
《International Dairy Journal》2007,17(3):190-198
Lactobacillus plantarum ST8KF, isolated from kefir, produced a 3.5 kDa bacteriocin (bacST8KF) active against Lb. casei, Lb. salivarius, Lb. curvatus and Listeria innocua. BacST8KF was sensitive to proteolytic enzymes, but stable between pH 2.0 and 10.0, and heat resistant (20 min at 121 °C). BacST8KF did not adsorb to the surface of the producer cell. Maximum activity (25,600 AU mL−1) was recorded in MRS broth with glucose, in MRS broth with glucose replaced by sucrose, and in MRS broth with glucose, supplemented with KH2PO4 after 24 h at 30 °C. Tri-ammonium citrate and glycerol in excess of 5.0 g L−1 repressed bacST8KF production. Production of bacST8KF increased from 800 AU mL−1 after 3 h of fermentation in MRS broth at 30 °C to 12,800 AU mL−1 after 9 h and to 51,200 AU mL−1 after 27 h. These results suggest that bacST8KF may be a secondary metabolite and shows that its mode of activity is bacteriostatic. 相似文献
11.
《International Dairy Journal》2003,13(10):821-826
The detection limits of 24 antimicrobial agents were determined in ewes’ milk by one commercially available version of brilliant black reduction test, BRT Inhibitor Test with prediffusion AiM® (BRT AiM®). For each drug, eight concentrations were tested on 20 milk samples from individual ewes. The detection limits of the BRT AIM® method were determined by means of logistic regression models: 6 μg kg−1 amoxycillin, 6 μg kg−1 ampicillin, 51 μg kg−1 cloxacillin, 2 μg kg−1 penicillin “G”, 230 μg kg−1 cefadroxil, 1330 μg kg−1 cephalosporin “C”; 270 μg kg−1 cephalexin, 92 μg kg−1 cefoperazone, 120 μg kg−1 ceftiofur, 69 μg kg−1 cefuroxime, 6000 μg kg−1 streptomycin, 1200 μg kg−1 gentamycin, 3700 μg kg−1 neomycin, 630 μg kg−1 erythromycin, 120 μg kg−1 tylosin, 390 μg kg−1 doxycycline, 5500 μg kg−1 oxytetracycline, 6200 μg kg−1 tetracycline, 5400 μg kg−1 sulfadiazine, 3200 μg kg−1 sulfamethoxazole, 6500 μg kg−1 sulfamethoxypyridazine, 6200 μg kg−1 sulfaquinoxaline, 22000 μg kg−1 chloramphenicol and 4100 μg kg−1 trimethoprim. The BRT AiM® method presents detection limits for β-lactam antibiotics that are similar to those obtained as Maximum Residue Limits (MRLs) according to Regulation 2377/90 EEC as set out by the European Union. However, for other antimicrobial agents the estimated limits were higher than those of the EU-MRLs. It is therefore advisable to enhance the sensitivity of the method for the detection of the different antimicrobial groups or to develop a combined system of different microbiological inhibitor tests that would enable the detection of a greater number of antimicrobial agents. 相似文献
12.
《International Dairy Journal》2006,16(1):52-60
Lactobacillus plantarum ACA-DC 146 and L. paracasei subsp. tolerans ACA-DC 4037 were examined for their potential application as adjuncts in the production of traditional Greek set-type yoghurt. Both strains displayed low milk acidification activity, while no inhibition was observed towards or from the yoghurt starters used. Yoghurt produced with L. paracasei subsp. tolerans ACA-DC 4037 exhibited the best sensory properties, with a rich traditional smooth taste, and the strain was selected for further trials. Yoghurt produced with this strain as an adjunct had good physicochemical properties. After 2 weeks of refrigerated storage, microbial loads (>7.0 log cfu g−1) were in accordance with international recommendations and guidelines for probiotic and starter cultures in milk products. Increasing the microbial load further, using concentrated and encapsulated inocula (10–11 log cfu g−1), gave yoghurt with long fermentation times and poor organoleptic properties. 相似文献
13.
《International Dairy Journal》2006,16(2):119-130
Seventeen strains of mesophilic lactic acid bacteria, isolated from cheese (non-starter lactic acid bacteria, NSLAB) or sourdough, were used individually as adjunct cultures in a Caciotta cheese model system. Adjunct cultures were monitored by randomly amplified polymorphic DNA analysis and their cell counts mainly varied from ca. 9.0 to 8.0 log cfu g−1 throughout 36 days of ripening. Adjunct cultures influenced differently cheese proteolysis. Both NSLAB and sourdough strains caused an extensive secondary proteolysis; however, some NSLAB strains produced the highest concentration of free amino acids. Principal component analysis (PCA) differentiated cheeses manufactured with NSLAB strains Lactobacillus parabuckneri B9FST, Lb. paracasei B61F5, Lb. curvatus 2768 and Lb. rhamnosus ATCC 7469 based on the accumulation of Lys, Glu, Phe, Hist, Asp and Met. Assessment of cheese lipolysis showed that: (i) highest concentrations of free fatty acids (FFA) were found with NSLAB strains Lb. rhamnosus ATCC 7469 and Lb. casei subsp. pseudoplantarum 2742 (ca. 10 500 mg kg−1); (ii) PCA differentiated cheeses manufactured with NSLAB strains Lb. rhamnosus ATCC 7469 and Lb. casei subsp. pseudoplantarum 2742 based on the accumulation of palmitic (C16:0) and linoleic (C18:2) acids, and those with Lb. curvatus 2768 and Lb. parabuckneri B9FST based on the high concentration of short chain FFA; (iii) the cheese made with sourdough strain Lb. sanfranciscensis CB1 had the highest levels of unsaturated FFA. 相似文献
14.
《International Dairy Journal》2007,17(11):1321-1331
In this study, the in vitro angiotensin-converting enzyme (ACE)-inhibitory (ACE-I) activity of peptide fractions from different yoghurt batches was assessed. Inhibition of ACE activity resulted in an overall antihypertensive effect. Yoghurts were prepared either using a sole yoghurt culture including Lactobacillus delbrueckii ssp. bulgaricus Lb1466 and Streptococcus thermophilus St1342, or L. acidophilus L10, L. casei L26 and Bifidobacterium lactis B94 in addition to yoghurt culture. ACE-I activity was determined at weekly intervals during 28 days of cold storage. Peptide fractions showing high ACE-I activity were further purified using multiple-steps of RP-HPLC. All probiotic yoghurts showed appreciable ACE-I activity during initial stages of storage compared with the control yoghurt, with a significant (p<0.05) decrease afterwards. The ACE-I activity ranged from IC50 of 103.30–27.79 μg mL−1 with the greatest ACE inhibition achieved during first and third week of storage. The in vitro ACE-I activity could be related to the peptide liberation via degradation of caseins. In total, 8 ACE-I peptides were characterized originating from αs2-casein (1), κ-casein (2) and β-casein, of which two well-known ACE-inhibiting peptides, namely Val–Pro–Pro (VPP) and Ile–Pro–Pro (IPP), were identified. These peptides are already used in commercial products. 相似文献
15.
《Food chemistry》1998,61(3):333-338
In-vitro binding of calcium (Ca) and magnesium (Mg) by total dietary fiber, hemicellulose A (HCL A), lignocellulose (LCL), cellulose (CL), and lignin (L) fractions isolated from rice bran (RB), wheat bran (WB), oat fiber (OF), apple fiber (AF) and tomato fiber (TF) was evaluated. At pH 6.8, significant amounts of Ca were bound by whole fibers, ranging from 800 μg g−1 for RB to 10 097 μg g−1 for TF. Mg bound by whole fibers varied from 496 μg g−1 for OF to 2177 μg g−1 for WB. Re-acid washing (pH<2.0) released 95–99% of the Ca and Mg bound to the fibers. Fibers with the highest endogenous Ca and Mg concentrations bound significantly (P<0.05) the highest amounts of the minerals studied. The Ca bound by HCL A varied from 9753 μg g−1 for RB to 11 337 mg g−1 for TF, whereas Mg bound varied from 1151 μg g−1 for OF to 5626 μg g−1 for TF hemicellulose fractions, respectively. Among the fiber components, Mg binding decreased in the order HCL A>LCL>L>CL, whereas Ca bound was in the order HCL A>LCL>CL>L. A relatively strong correlation was observed between the combined effects of protein content, hemicellulose, and lignin vs total Ca and Mg bound. 1998 Elsevier Science Ltd. All rights reserved 相似文献
16.
The goal of this work was to investigate the physicochemical properties of methylcellulose (MC) based films as stabilizers of two strains of lactobacilli: Lactobacillus delbrueckii subsp. bulgaricus CIDCA 333 and Lactobacillus plantarum CIDCA 83114. The incorporation of 3% w/v fructo-oligosaccharides (FOS) into the MC film formulation improved the viability of L. delbrueckii subsp. bulgaricus CIDCA 333 after film preparation. L. plantarum CIDCA 83114 was intrinsically more resistant as no viability loss was observed upon preparation of the films in the absence of FOS.Scanning electronic microscopy images also showed a good incorporation of microorganisms without affecting the homogeneity of the films. FTIR spectroscopy provided structural information about the bacteria-loaded films. Water sorption isotherms showed an impervious behavior at low aw but on exceeding 0.7 of aw the film started to dissolve and form syrup, causing a drastic drop of bacterial viability (log N/N0 ≤ − 5). Dynamic mechanical analysis (DMA) demonstrated that the incorporation of microorganisms into the MC films had no effect on vitreous transition temperatures. FOS incorporated into the MC films had a plasticizing effect.Microorganism-loaded films were stored at relative humidities (RH) ranging from 11 to 75%. Both strains could be stored at 11% RH for 90 days. At 33 and 44% RH L. delbrueckii subsp. bulgaricus CIDCA 333 could be stored up to 15 days and L. plantarum CIDCA 83114 up to 45 days. At 75% RH only L. plantarum CIDCA 83114 could be equilibrated (log N/N0: − 2.05 ± 0.25), but CFU/g films were undetectable after 15 days of storage.The results obtained in this work support the use of MC films containing FOS as a good strategy to immobilize lactic acid bacteria, with potential applications in the development of functional foods. 相似文献
17.
C.P. Champagne J. Green-Johnson Y. Raymond J. Barrette N. Buckley 《Food research international (Ottawa, Ont.)》2009,42(5-6):612-621
Lactobacillus delbrueckii subsp. lactis R0187, Lactobacillus helveticus R0052, Lactobacillus rhamnosus R0011 and Bifidobacterium longum R0175 were examined for their ability to grow in combination with Streptococcus thermophilus cultures in milk and a laboratory soy beverage (LSB; both standardized to 4.5% protein and 2.3% fat). Strains R0011 and R0187 did not rapidly acidify the soy beverage despite good growth rates on soy carbohydrates. The S. thermophilus populations in the LSB were similar to that of milk even though milk had 30% more buffering capacity. In milk but not in soy, symbiosis with respect to acidification rate was observed between S. thermophilus and L. helveticus or B. longum. The populations of L. helveticus in the fermented products were similar in pure cultures or in the presence of the streptococci. However B. longum did not compete well in the mixed culture. Fermentation conditions varied as a function of the ability of S. thermophilus strains to acidify media to a pH of 4.65 (between 8 and 24 h). The probiotic populations in the mixed culture were influenced by the S. thermophilus strain and by the time of fermentation. Variations in growth rates of the bacteria did not appear to be linked to differences in initial redox or α-amino nitrogen levels. Strain selection enabled the preparation of a mixed starter, probiotic-fermented soy beverage containing 1.1 × 108 CFU/mL of L. helveticus R0052, which represented approximately 13% of the total final population. 相似文献
18.
《International Dairy Journal》2007,17(6):657-665
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). 相似文献
19.
《International Dairy Journal》2005,15(1):51-57
The antimicrobial activity of two pediocin-producing transformants obtained from wild strains of Lactococcus lactis on the survival of Listeria monocytogenes, Staphylococcus aureus and Escherichia coli O157:H7 during cheese ripening was investigated. Cheeses were manufactured from milk inoculated with the three pathogens, each at approximately 6 log cfu mL−1. Pediococcus acidilactici 347 (Ped+), Lc. lactis ESI 153, Lc. lactis ESI 515 (Nis+) and their respective pediocin-producing transformants Lc. lactis CL1 (Ped+) and Lc. lactis CL2 (Nis+, Ped+) were added at 1% as adjuncts to the starter culture. After 30 d, L. monocytogenes, S. aureus and E. coli O157:H7 counts were 5.30, 5.16 and 4.14 log cfu g−1 in control cheese made without adjunct culture. On day 30, pediocin-producing derivatives Lc. lactis CL1 and Lc. lactis CL2 lowered L. monocytogenes counts by 2.97 and 1.64 log units, S. aureus by 0.98 and 0.40 log units, and E. coli O157:H7 by 0.84 and 1.69 log units with respect to control cheese. All cheeses made with nisin-producing LAB exhibited bacteriocin activity throughout ripening. Pediocin activity was only detected throughout the whole ripening period in cheese with Lc. lactis CL1. Because of the antimicrobial activity of pediocin PA-1, its production in situ by strains of LAB growing efficiently in milk would extend the application of this bacteriocin in cheese manufacture. 相似文献
20.
《International Dairy Journal》2007,17(2):157-166
A semi-hard cheese produced from milk artificially contaminated with Clostridium tyrobutyricum spores (2.5×103 mL−1) was used as a model for studying the ability of bacteriocin-producing Lactobacillus gasseri K7 (Rifr) to inhibit clostridia. The added lactobacilli did not inhibit the primary starter culture (Streptococcus thermophilus), but inhibited non-starter mesophilic lactobacilli. Late blowing as a result of Cl. tyrobutyricum outgrowth and butyric acid fermentation occurred in all cheeses however it was reduced in cheeses with added Lb. gasseri. After 6 weeks, the average amount of butyric acid was significantly higher in cheeses without added lactobacilli (1.43 vs. 0.70 g kg−1). At the end of 8-weeks ripening, 2.8×107 cfu g−1 of K7 (Rifr) viable cells were detected. Using the total DNA from cheeses with added K7 (Rifr) strain, PCR products were amplified with primers specific for Lactobacillus, Lb. gasseri and K7 bacteriocin gene. 相似文献