STARTER FOR FERMENTATION OF PLANT MATERIAL |
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| 申请号 | EP03700826.5 | 申请日 | 2003-01-30 | 公开(公告)号 | EP1478245B1 | 公开(公告)日 | 2006-05-10 |
| 申请人 | Maa- Ja Elintarviketalouden Tutkimuskeskus; Arktinen Bio-Lacto OY; Bioferme OY; Savimäki OY; | 发明人 | JOUTSJOKI, Tiina; TAMMINEN, Marja; MÄKI, Maarit; VIANDER, Britta; RYHÄNEN, Eeva-Liisa; | ||||
| 摘要 | The present invention provides a starter (starter strain mixture) for controlled fermentation of vegetables, fodder and other plant-derived material, which starter comprises lactic acid bacterial strains acting in a way similar to the natural spontaneous lactic acid fermentation. The invention also provides a lactic acid bacterial strain being isolated from plant material, and presumably having probiotic characteristics. | ||||||
| 权利要求 | |||||||
| 说明书全文 | The present invention provides a starter (starter strain mixture) for fermentation of vegetables, fodder and other plant-derived material, which starter comprises lactic acid bacterial strains acting in a way similar to the natural spontaneous lactic acid fermentation. By means of the starter mixture it is possible to prepare in a controlled way fermented vegetables of good flavour and of good and uniform quality. The invention also provides a lactic acid bacterial strain being isolated from plant material and presumably having probiotic characteristics. Commercial vegetable fermentations are still generally carried out by means of the natural microbial flora of the plant to be fermented. This substantially increases production costs, because succeeding of the fermentation may be random, and the time of processing is usually long and dependent on the initial flora and the progress of the microbial succession. From naturally fermented vegetables lactic acid bacteria have been isolated and characterised (Valdez et al., 1991), and so it has already been known for a long time, which bacteria are present in fermented plant materials. These bacteria have been investigated, and efforts have been made to find out suitable starter strain mixtures (Purtsi et al., 1999; Gardner et al., 2001) and to optimise the mutual amounts of the strains included in such mixtures (Savard et al., 2000). However, very few commercial starter bacteria strains for vegetable fermentations are available, and no Finnish strains at all. In addition, use of commercial starters is restricted because of the lack of basic information about the microbiology of such fermentations in domestic vegetable material. Preservation of vegetables by fermentation, exploiting lactic acid bacteria, is an old method. Consumers may consider these products natural and healthy. The vitamin and mineral contents of fermented vegetables depend on the corresponding contents of the starting material. During the fermentation carbohydrates are degraded and proteins are digested by the action of organic acids, whereby the digestibility of the products is improved. Organic acids may also further the absorbance of minerals, especially iron (Eriksson, 1991). The amount of various vitamins, except thiamine, riboflavin, niacin, folic acid and B12-vitamin, as well as K-vitamin (McFeeters, 1993) is decreased during the fermentation. Salt enhances the fermentation process, and keeps the texture of the sauerkraut solid (Sillanpää, 1984). However, abundant amount of salt is detrimental to health. It has been found in studies made using cancer cells (in vitro) and laboratory animals that glucosinolates and their degradation products present in cabbage plants have anticarcinogenic effects. Degradation products of glucosinolates have prevented the growth of some bacteria and yeasts (Ryhänen et al., 2001). The health-promoting activity of fermented products is apparently primarily connected with the function of intestines. The balancing effect of probiotic lactic acid bacteria to e.g. disturbed intestinal microbial flora is well known (Gorbach, 1990), and the probiotics have been supposed to decrease the serum cholesterol, improve immune response and relieve allergies. In addition, lactic acid bacteria reduce the activity of such enzymes, which activate cancer-producing compounds (Sanders 1998, Ziemer and Gibson 1998). According to the new nutritional recommendations use of vegetables in the everyday diet should be increased. Various compounds (including dietary fibres, antioxidants and flavonoids) included in plants are believed to be of significance to health. Although probiotics are abundantly used in dairy products, and clinical evidence of their health effects exists, with vegetables produced my means of probiotic bacteria clinical tests corresponding to those made with probiotic dairy products have not been made. If fermented vegetables could be produced by means of probiotics, it would diversify the present selection of vegetables and further the increase in vegetable use. The starter developed for fermenting plant material has characteristics, which enable fermentation similar to spontaneous lactic acid fermentation in vegetables. In the spontaneous lactic acid fermentation the fermentation is started by Leuconostoc mesenteroides, whose growth is prevented, when the acidity increases. The acid-tolerating Lactobacillus plantarum and Lactobacillus brevis strains survive. Fermentation occurs in liquid phase, into which the nutrients needed by the bacteria for growth are dissolved. Fluid and nutrients can be released from the plant cells by means of osmotic pressure, i.e. adding salt. Salt acts also as a preserving agent by favouring lactic acid bacteria and by preventing the growth of contaminating microbes. Fermentation occurs in anaerobic conditions, whereby the production of lactic acid is most efficient. A starter for vegetables should meet, among others, the following requirements:
The starters used today are of two different types:
The starter (starter strain mixture) according to the present invention, which is in the present invention designated as "Ferme starter strain mixture", is a mixture of three lactic acid bacterial strains, wherein the lactic acid bacteria have a synergistic effect on the characteristics of the product to be prepared. The strains included in the starter strain mixture are:
When characterising the strains, they were found probably to belong to the above-mentioned species. In the following primarily the above-mentioned probable species names thereof are used. In principle, the starter acts in a similar way independent on the plant material to be fermented and the cultivation time. The cultivation temperature should be kept in the region 18-35°C, since the strains according to the invention are mesophilic. Nutrients needed for fermentation should also be available. This is ensured in the preparation of sauerkraut and fermented cucumber by adding salt. When fermenting carrot juice or other juices the nutrients are already in the liquid. The starter is added into the material to be fermented either as a freeze-dried powder or as pre-cultivated in vegetable juice. The fermentation is started by the homofermentative Pediococcus pentosaceus P45 and the heterofermentative Leuconostoc mesenteroides 78. The region of the pH-optimum of P. pentosaceus is higher than that of Lc. mesenteroides and Lactobacillus paraplantarum. Hence it produces lactic acid more effectively in the beginning of the fermentation, when pH is almost neutral. The growth of P. pentosaceus is prevented, when pH falls below 4, whereby the fermentation is continued by Lc. mesenteroides and L. paraplantarum. Lc. mesenteroides is an aroma former, which produces lactic and acetic acid, as well as carbon dioxide from the fermentable substrates. In addition, it produces aromatic compounds. Acetic acid is weaker acid than lactic acid, wherefore Lc. mesenteroides alone cannot ensure sufficiently effective lactic acid production in the beginning of the fermentation. This is ensured by means of P. pentosaceus which, on the other hand, does not form aromatic agents. A homofermentative acid-enduring strain L. paraplantarum 2* remains at the end of the fermentation as the dominant strain, which also effectively produces lactic acid. This strain is suitable for fermentation of plant material. On the other hand, it has been shown in in vitro conditions that it survives in human intestines and is able to attach on the intestinal surface, wherefore it apparently has probiotic characteristics. It should be noted that the strain Pediococcus dextrillicus 9/PX3 may be used in the starter according to the invention instead of Pediococcus pentosaceus P45, but its use in the starter is restricted by its weak competitive capacity with other strains. Consequently, the present invention relates to a culture as claimed in claim 1 and to the use of it in fermentation of plant material, i.e. vegetables, fodder and other plant-derived material, especially cucumbers. Into the pure culture of the Lactobacillus sp. 2* (DSM 14485) the bacterial strain Pediococcus pentosaceus P45 (DSM 14488) and the strain Leuconostoc mesenteroides 78 (DSM 14486) may be added to form a starter adapted for use in fermentation of plant material. In specific, the invention concerns a pure culture of the strain Lactobacillus paraplantarum 2* and use of this strain in a starter adapted for use in fermentation of plant material. In addition, the invention concerns a process for fermenting plant material, in which process the plant material to be fermented is contacted with the starter strain mixture according to the invention, and the plant material is fermented in room temperature for about 1 d to 14 d in anaerobic or microaerophilic conditions until achieving a desired acid content, which is dependent on the product and varies from about pH 3.5 to pH 4.5. Use of the starter strain mixture according to the invention as a starter was found to accelerate the fermentation by enhancing development of lactic acid in the beginning of the fermentation. By means of the starter, products of good quality were obtained, the texture or taste of which were faultless. This resulted in secured lactic acid fermentation and products of uniform quality. Presumably the products also have probiotic activity: the stress tolerance and the adhesion to mucus of the strain Lactobacillus paraplantarum 2* were proven to be good.
26 lactic acid bacterial strains were isolated from spontaneous fermentation of fermented cucumbers in different phases of the fermentation. The strains were identified on the basis of a DNA test, an API test (usage of sugars) and on the basis of microscopy. Most of the isolated strains were Lactobacillus plantarum, in addition, a few Lactobacillus pentosus and Lc. mesenteroides strains were found. Besides these tests the strain was identified at VTT by means of ribotyping, whereby it was found that it is presumably Lactobacillus plantarum. Lactobacillus sp. 2* was later identified as the species Lactobacillus paraplantarum by means of a species-specific PCR method (Torriani et al., 2001). The PCR reaction gives a 107 bp product, whereas Lactobacillus plantarum and Lactobacillus pentosus give 318 and 218 bp products, respectively. The strain was deposited according to the Budapest Treaty in DSMZ depositary (Deutsche Sammlung von Mikroorganismen und Zellkulturen, GmbH) 31 August 2001 with the deposit number DSM 14485. Lactic acid bacterial strains were isolated from different phases of the spontaneous fermentation of sauerkraut. This strain was identified by means of a DNA test, an API test and ribotyping, and it was found that it is presumably Leuconostoc mesenteroides. The strain was deposited according to the Budapest Treaty in DSMZ depositary (Deutsche Sammlung von Mikroorganismen und Zelikulturen, GmbH) 31 August 2001 with the deposit number DSM 14486. New starter strains were isolated from grass, which was preserved in bottling jars and incubated at 21, 30 and 45°C. Samples were taken after 1 and 2 days. In specific, a P. pentosaceus strain of our own was searched, which would replace the strain P. pentosaceus DSMZ 20333 used in the clinical study. Besides physiological and biochemical tests, an API test was used in the identification of the strains. We succeeded in isolating a P. pentosaceus P45 strain, which is well suited for vegetable fermentation, from grass, which had been incubated at 45°C. The strain was deposited according to the Budapest Treaty at DSMZ depositary (Deutsche Sammlung von Mikroorganismen und Zellkulturen, GmbH) 31 August 2001 with the deposit number DSM 14488. Lactic acid bacterial strains were isolated from different phases of spontaneous fermentation of sauerkraut. The strain was identified by means of an API test, physiological and biochemical tests and ribotyping, and it was found that it is presumably Pediococcus dextrinicus. The strain was deposited according to the Budapest Treaty at DSMZ depositary (Deutsche Sammlung von Mikroorganismen und Zellkulturen, GmbH) 31 August 2001 with the deposit number DSM 14487. Results of the API test for the above-mentioned strains are depicted in Table 1. RiboPrint fingerprints confirmed the identification of the strains. Suitability of the bacterial strains as probiotics was tested in in vitro conditions in the Universities of Helsinki (HY) and Turku (TY). L. paraplantarum 2* turned out to be the most resistant of the four strains tested in the stress tolerance tests. Lc. mesenteroides 78 showed very good resistance as well. The adherence of the strains to human intestines was tested in the University of Turku. L. paraplantarum 2* showed distinct adherence, whereas Leuconostoc sp. 78 was only slightly adherent. Tolerance of lactic acid bacteria to pancreatic juice and bile salts was tested in the Department of Food Technology of University of Helsinki. The strains were cultivated in MRS broth and the determinations were made in duplicate.
The results of the stress tolerance tests are given in Figures 1a and 1b. Both Lc. mesenteroides 78 and L. paraplantarum 2* showed good tolerance to bile salts and pancreatic juice. They survived at pH 4, but at pH 2 their number had decreased substantially, although their growth was not totally prevented. Adhesion of the strains L. paraplantarum 2* and Lc. mesenteroides 78 to human intestinal mucus was tested in the Department of Biochemistry and Food Chemistry of University of Turku. The bacteria were grown overnight in MRS broth (Merck, Darmstadt, Germany) at 37°C without oxygen. To metabolically label the bacteria, 10 µl of methyl-1,2[3H]thymidine (6.7 Ci.mmol-1; Nen products) was added per ml of growth medium. The bacteria were harvested by centrifugation (1000 x g), washed with HEPES (N-2-hydroxy-ethylpiperazine-N'-2-ethanesulphonic acid)-Hank-buffer (HH; 10mM HEPES; pH 7.4), and resuspended in HH-buffer. The absorbance at 600 nm was adjusted to 0.25 ± 0.01, and diluted then 10-fold in HH buffer (about 107 CFU/ml) in order to avoid substrate saturation (Tuomola and Salminen, 1998). Mucus was prepared from the healthy part of human colon, as earlier described (Ouwehand and Conway, 1996). Briefly, immediately after the resection the colon was placed on ice, and it was used within 20 minutes. The piece of colon was cut open and gently washed in HH buffer. The mucus was scratched out with a rubber spatula and centrifuged twice in order to remove particulate material. The mucus was stored at -70°C until use. For the adhesion study (Ouwehand et al., 1999) the mucus was diluted into protein concentration of 0.5 mg.ml-1 and passively immobilised on microtitre plate wells by overnight incubation at 4°C. Excess mucus was washed out with HH buffer and the radioactively labelled bacteria were added into four parallel wells. The bacteria were incubated at 37°C and after 60 minutes the wells were washed to remove the non-adhered bacteria. The adhered bacteria were released and lysed by incubation with 1% SDS in 1M NaOH at 60°C for 60 min. Adhesion is expressed as percentages: radioactivity recovered from the wells compared to radioactivity added to the wells. For the determination mucus of three individuals was used, and the determinations were made at least in triplicate. Health effects of the products prepared with a starter strain mixture containing the bacterial strain according to the invention, Lactobacillus paraplantarum 2*, were studied at the Department of Clinical Nutrition of University of Kuopio. Nutritional characteristics and health effects of the fermented vegetables were examined in the study. The study was supposed to reveal, whether the vegetables fermented with probiotic bacterial strains produce more health-promoting effects than products prepared by ordinary fermentation. No corresponding clinical studies have been made concerning adding probiotic bacterial strains to vegetables. The results are currently being processed. The research gives new information about health effects of fermented vegetables. In addition, the health effects of products fermented with conventional methods and those fermented with probiotic bacterial strains may be compared to diets not containing such products. Four products were used in the clinical study: sauerkraut, sauerkraut juice, grated swede and carrot juice, which were prepared in two phases. For all products to be tested a corresponding control product was prepared. The products to be tested are called below as "probiotic" products. Carrot juice was pressed and transferred to a freeze store of -20°C. The juice was thawed overnight at a refrigerator temperature and autoclaved at 121°C for 20 min. pH of the juice was 5.42. Growth of the following strains in carrot juice was monitored in the test:
The strains were passaged overnight in MRS broth at 30°C and inoculated with 1% inoculum into carrot juice. The juices were fermented for 21 h at 30°C. pH of the juices were measured and the lactic acid bacterial counts were determined on MRS medium both from the strains cultivated in MRS broth and those cultivated in carrot juice (Table 3). The juices were packed into bottles. The juices were used for preparing the grated swede for the clinical study. The grated swede was fermented with a starter strain mixture containing L paraplantarum 2*, Lc. mesenteroides 78 and P. pentosaceus DSMZ 20333. Subsequently, the activity of the strains cultivated in carrot juice inoculum was tested by correspondingly inoculating 1% of an inoculum to autoclaved carrot juice. The starters used in the clinical study were selected for the experiment. (Table 4). The strains were grown at 30°C for 18.5 h. Sauerkraut was prepared and packed into 100 g sachets in 20% carbon dioxide protecting gas for the first and for the second intervention at different times. As an additive 1% PVD vacuum salt + E535, Saltunion, Algol, was used. In addition, 1% of starter cultivated in carrot juice was added into the probiotic sauerkraut. The starter was a mixture of three strains: L. paraplantarum 2*, Pediococcus pentosaceus DSMZ 20333, Lc. mesenteroides 78. Was prepared by expressing from the above sauerkraut batch. The juice was packed into 2 dl cartons for the first intervention. 27% of carrot juice was added into the control sauerkraut juice before packing. L. paraplantarum 2* strain was added into the probiotic sauerkraut juice, so that 1.2 litres were added as a concentrate, and about 6 l as fermented carrot juice. The concentrate had been prepared by centrifuging carrot juice fermented by an inoculum of L. paraplantarum 2*. In addition, 2.5 litres of non-fermented carrot juice were added. Altogether, 20% of carrot juice was added. The probiotic juice became very sour, whereas the control juice was milder. The control sauerkraut juice was stored in 10 l plastic canisters in a cold store at +5°C for the second intervention. A precipitate had gathered at the bottom of the bottle, and care was taken not to blend the precipitate into the juice. A day before packing 25% of fresh carrot juice was added into the juice. The probiotic sauerkraut juice was stored at -25°C and thawed in a cold store for 2 d. The precipitate gathered at the bottom was not totally mixed with the juice. A day before packing 25% of fresh carrot juice was added into the juice. In addition, just before packing about 1 litre of the strain L. paraplantarum 2* grown in carrot juice was added as a concentrate. The juices were packed. The grated swede was prepared separately for both of the interventions. The grate was fermented in brine so that into 60 kg of grate 60 litres of seasoned brine was added. While packing, the brine was run apart and about 5 g of it was added at the bottom of the bag. The grates were packed under 20% carbon dioxide protection gas. Raw materials included swede, carrot and onion in proportions 4:1:0.1, and the spices: fructose, anise, fennel, caraway, coriander, chives, marine salt (the broth included 1% of salt). The control grate was prepared by adding a "wild strain inoculum" or a mixed starter prepared from sauerkraut juice. The probiotic grate had been prepared by adding 1% of the mixture of the three strains, in a way similar to that used in preparing sauerkraut. Raw materials were swede, carrot and onion + leek in proportions 1:1:0.2 and the spices fructose, anise, herbs de provence and marine salt (the broth included 1% of salt). Carrot juice was prepared separately for both of the interventions. The starters were the same as in preparing the grated swede. The strain L. paraplantarum 2* was added to the probiotic juice as a concentrate. The acidity of the carrot juice was adjusted by adding ordinary carrot juice. The juice was packed into 2 dl cartons. Chemical analyses of the products were made in the chemical laboratory of MTT. The analyses were carried out separately for both of the test phases, since the products had been prepared using different raw material batches. Microbiological analyses for the products were carried out in the Laboratory of Food Chemistry and Technology of MTT in the beginning and at the end of the test phases (Tables 5 and 6). 40 individuals of the test subjects announced to the clinical study were invited into an interview, 25 of which were selected for the study. 22 test subjects kept up in the study from beginning to the end. The study lasted for four months. After a 2-week basic period there was a 4-week intervention, a 4-week recovery period and a 4-week intervention. Samples were taken thrice. The test subjects kept food diary for three days, and they also replied to an inquiry of exercise habits. The test products were grated swede and sauerkraut, as well as carrot juice and sauerkraut juice. The test subjects obtained their weekly portions frozen, and they took 2 dl of juice and 100 g of grate daily. The test subjects were allowed to decide themselves, in which order they took the products. The test subjects assessed the sensory characteristics of the carrot juice and grated swede in the beginning and at the end of the study. A first evaluation was made of a fresh product and the latter of a frozen same product. The grated swede, which had been prepared using the starter, the probiotic characteristics of which were examined, was somewhat more pleasing than the control grate, although there was no statistical difference between them. In the latter evaluation time there was no difference between the characteristics. The general acceptance of the fresh carrot juice prepared with the probiotic starter was significantly better than that of the control juice. In the latter evaluation time there was no difference. At both times the evaluation grades were at the same level. The test subjects gave mostly positive feedback for the products. However, the sauerkraut juice was, especially in the first phase, very sour, and the test subjects took it as diluted. When packing, carrot juice had been added into the sauerkraut juice, but it did not sufficiently decrease the acidity. The carrot juice of the latter phase had a little bitterness, but the test subjects did not complain of that. Caraway added into the grated swede was a strange spice for the test subjects from eastern Finland, and it was found a little peculiar. Chemical analyses of the products were made in the chemical laboratory of MTT. The analyses were carried out separately for both of the test phases, since the products had been prepared using different raw material batches. Microbiological analyses for the products were carried out in the Laboratory of Food Chemistry and Technology of MTT in the beginning and at the end of the test phases. No statistical differences in the cholesterol values of the test subjects could be found, although the mean value decreased a little. The cholesterol values of all of the test subjects were good, and it was difficult to find any changes. According to the results the HDL level did not change, whereas the LDL level decreased a little. In small blood picture no statistically significant changes between the groups could be found, and all of the test subjects were healthy. β-carotene level increased statistically significantly in both of the groups, and a little more in the probiotic group. There was no difference between the control and probiotic groups in the total bacterial count or lactic acid bacterial count. In each of the test subjects it was found that in May the total bacterial count had decreased and the lactic acid bacterial count had increased. This may be due to both environmental factors and differences in the raw materials of the products. According to the results the amount of cresols causing skin cancer and possibly also intestinal cancer, decreased both in the control and in the probiotic group. There was no difference between the groups. At the end of the second test phase the amount of the cresols had strongly decreased. The order, in which the test was started, had no effect on the cresol amounts. The amounts of phenols did not show statistical differences between the groups, although the level in the probiotic group was a little lower. The amount of phenols decreased at the end of the second test phase in the same way as the amount of cresols. There were no differences in the β-glucuronidase levels between the groups. In future it will be studied, if the changes in the cresol and phenol amounts could be explained by the levels of the bacterial counts. The analysis of the results is still going on. Taking the products during the test phases did not show any harmful effects to health. The MRS plates cultivated of the faeces samples in Kuopio had been sent to the MTT Food Research by mail, and colonies were isolated and purified from the dishes. Totally 110 samples were sent, and from each of the samples 3-7 different colonies were collected. Purified strains amounted to 334, 93 of which turned out to be L. plantarum strains. Before the test phase only from one sample one L. plantarum strain could be isolated. During the first test phase the amount of the L. plantarum strains isolated from the faeces increased up to thirty. Also during the second phase the amounts kept higher compared to the initial level. In the future it will be examined if there were differences between the probiotic and the control groups. In addition, it will be examined if the strains can be identified as the strain L. paraplantarum 2 *, added as a probiotic. In the Bioproduction Unit of University of Turku freeze-dried starter had been produced out of the strains L. paraplantarum 2* and Lc. mesenteroides 78 used in the clinical study, and the strain P. pentosaceus P45 isolated in June. The suitability of the mixture containing these three strains (Ferme starter strain mixture) in preparing fermented cucumber was tested in the preliminary test carried out in June, and in the actual tests carried out in July-August. Tests were carried out both in laboratory and in practical scale. Cucumbers for the tests were obtained from MTT/Horticultural Research in Piikkiö, where the variety Crispina had been cultured for this test. The cucumbers were preserved in aluminium bags, bottling jars and Ilves-jars. The aim was to avoid the access of air to the containers during the preservation. The fermentation was monitored by means of pH measurements and titratable acidity. Microbial determinations were made in the beginning and at the end of the fermentation. Dilution water: Ringer solution, strength ¼ (Merck), sterilisation in autoclave at 120°C for 20 min, divided into sterile test tubes à 9 ml. Coliformic enterobacteria: VRB-agar (Biokar Diagnostics BK 086), 0.1% of glucose was added, poured plates, pouring a layer of the medium on the surface, incubation at 30°C for 2 d. Lactic acid bacteria: MRS-agar (Bacto Lactobacilli MRS broth, Difco 0881-15-5, 1.5% agar), streaked plates, anaerobic incubation for 3 d at 30°C. Yeasts and moulds: YGC-agar (Difco 1900-17, Bacto yeast extract glucose chloramphenicol agar), streaked plates, incubation at 30°C for 3 d.
Statistical differences were calculated with unidirectional variance analysis separately for each sampling time. Mean values for the treatments were calculated as least square means and deviations as standard error of means (s.e.m.). Mean values were compared in pairs by the means of contrasts. Statistical analyses were calculated using the SAS/STAT program, version 8.1. (SAS Institute Inc., Cary, NC, USA). Statistical analysis of sensory evaluation is described separately. Growth of the starter strains was compared in MRS broth and cucumber brine. The strains tested were:
pH and titratable acidity of the broths were examined. The cucumbers (variety Crispina) were preserved one-by-one in aluminium bags and in 1 l bottling jars. Suitability of the aluminium bags had been tested in the preliminary tests. On the basis of the preliminary test Pediococcus sp. P45 was selected to the starter strain mixture. Ferme starter strain mixture was compared to the control and to the starter Bioprofit (Valio Oy). Bioprofit consists of Lactobacillus rhamnosus and Propionibacterium freudenreichii strains. The starter is used as a protective culture in milk products and as a starter for ensilage. Brine was added as the amount of the weight of the cucumbers. The brine was prepared of marine salt by boiling and cooling to room temperature. Salt concentration was 3%. Results were statistically compared by means of contrasts (F-test). Ferme starter strain mixture decreased pH statistically significantly more effectively, and produced lactic acid more effectively after 3 d preservation compared to the control (Table 8). pH of the control cucumbers had decreased almost to the same level within 5 d and the lactic acid amounts were almost the same as in the cucumbers preserved with the starter strain mixture (Table 9). In the test the effect of dosage levels of a freeze-dried starter prepared of Ferme starter strain mixture to the fermentation rate was compared. The starter was added in proportions 1:1:1 in three different levels 105, 106, 107 cfu/ml. The fermentation rate was compared to that of the control prepared without the starter. The brine was prepared of marine salt (3%) by cooking into tap water. Water was cooled to room temperature. Cucumbers, which were of the variety Crispina, had been picked up and brought on the previous day from Piikkiö from a field cultured for the test. The cucumbers were stored overnight in a cold store and washed with a scrubbing-brush, rinsed thoroughly and weighed into aluminium bags. A same amount of brine, with which the starter had been mixed, was added into the bags. There were three sampling times, and 5 parallel samples were reserved for each sampling time. Weight of the cucumbers varied from 31 g to 66 g. The samples were incubated in the fermentation room at 21°C and the samples were taken after 2, 4 and 10 days. pH was measured separately from each of the cucumber juices, and the titratable acidity from a pooled sample. The statistical differences of the pH results and weight of the cucumbers were analysed by variance analysis, and the differences were examined by means of contrasts. There were no statistically significant differences in the weights of the cucumbers. According to the variance analysis the pH of the cucumbers did not show significant differences after two days, but analysed by means of contrasts, at the starter level of 107 cfu/ml it was possible to decrease pH significantly more effectively (P=0.0134) compared to the control. At the starter level of 105 cfu/ml, pH did not decrease more efficiently after 4 days compared to the control, whereas at the starter levels of 106 and 107 cfu/ml the difference was significant (P=0.0144 and P=0.0002, respectively). The starter level 107 cfu/ml was significantly more effective than 106 cfu/ml (P=0.0112). After 10 days the starter and the control did not show statistically significant differences. The results are given in Figures 2a and 2b. According to the results the dosage of the freeze-dried starter in the brine has to be on the level of 107 cfu/ml, if it is desirable to accelerate the fermentation of cucumbers in the beginning of the preservation. In the experiments the fermentation activities of freeze-dried and fresh starters were compared. In the first experiment, which was later subjected to sensory evaluation (see below), the control (brine + 1% cucumber juice), a 1% starter strain mixture 1:1:1 (g) grown overnight in sterile (autoclaving at 120°C, for 20 min) cucumber juice (the strains had been grown separately), and 107 cfu/ml freeze-dried 1:1:1 (cfu/g) starter strain mixture. The freeze-dried starter had been prepared in the Bioproduction Unit of University of Turku. The amount of the starter was calculated so that the brine would include an inoculum of 107 cfu/ml (Table 10). The freeze-died starter was first diluted in 200 ml of water, and 1800 ml of brine was added thereto. The final concentration in the brine was numerically (200 ml x 1.05 x 108 cfu/ml)/2000ml=1.05 x 107 cfu/ml. The cucumbers (variety Crispina) had been brought from Piikkiö, stored overnight in a cold store, washed on the next day and stored in water in a cold store. The brine was prepared by cooking marine salt (3%) in tap water. The cucumbers 5-6 pieces (about 400 g) were weighed into aluminium bags, wherein a same amount of brine was added. The starter had been dissolved in brine. Air was removed as carefully as possible, and the bag was closed with a heat sealer. A sample was taken from the brines into 100 ml plastic bottle for colony determination, and it was analysed next day. The cucumbers were incubated in the fermentation room at 21°C for 16 days and placed into a cold store at 5°C. pH and titratable acidity of the cucumbers were measured after 6 days (Table 11). The control cucumbers had produced gas and the bags were very distended. The cucumbers preserved with the freeze-dried starter were distended as well, whereas those preserved with the fresh starter were distended only a little. In the experiment the effect of the starter to a control preserved without a starter in 4 l bottling jars (Ilves jars) was compared. The cucumbers were picked up and brought the next day to Jokioinen. The cucumbers were washed and stored in water in a cold store at 5°C. Cucumbers weighing 75-125 g were selected for the experiment. The experiment was carried out in two parallel jars. The brine (3%) was prepared of marine salt (Meira) by cooking and cooling into room temperature (16.6°C). The starter was added as a freeze-dried powder into the brine (Table 12). The jars were filled with cucumbers (mean 1.925 kg) and brine was added so much that no air was left under the intermediate cap (mean 1.647 kg). The colony number of the brine was determined on the same day on MRS medium. The cucumbers were incubated for 18 d at 21°C in an incubation room. Samples of the cucumber brine were taken with a scale pipette, 50 ml from the surface and from the bottom. pH, titratable acidity, lactic acid bacteria, coliform enterobacteria, as well as yeasts and moulds were determined from the cucumbers (Table 13). According to the results, the starter addition increased lactic acid production and prevented growth of coliformic enterobacteria, as well as yeasts and moulds. Both the control and the starter cucumbers were hollow, but the starter cucumbers were not as flattened, and their taste was better. Lactic acid bacteria grown on an MRS plate were rods in each of the samples (10 colonies per sample). In the sensory evaluation test cucumbers prepared with the freeze-dried starter according to this invention (Ferme starter strain mixture: Lc. mesenteroides 78, P. pentosaceus P45 and L. paraplantarum 2*) were compared to control cucumbers of the same producer and to cucumbers of two different producers prepared with the same freeze-dried starter. The preservation of the cucumbers is described above in item 3. The producers were given instructions to add 10 g of each of the strains to 100 ml of brine, i. e. the starter was added altogether in an amount of 30 g. Hence the starter level of 107 cfu/ml of brine was obtained. For chemical and microbiological determinations samples were taken of the brine. The microbiological determinations were carried out on the sampling .day. For the chemical determinations the brines were frozen at -20°C, were taken to thaw in a cold store at 5°C and analysed after two days. The sensory evaluation was carried out in the sensory evaluation laboratory of MTT, and for tasters the staff of EKT was recruited, altogether 23 persons. The evaluations were carried out during forenoon. There were 6 cucumbers to taste. The fermented cucumbers were flushed with tap water and sliced with a slicing machine to slices of about 2 mm thick. The cucumbers were evaluated in random order according to their code numbers. In the evaluation form the pleasantness of the cucumbers was inquired, but there was no request to compare the cucumbers with each other. The reviewers marked a line on the scale to the point, which best corresponded to their liking. The length of the segment of the line was measured and used as the evaluation result, the tolerance of which was 0-90 mm. The hygienic quality of the cucumbers was good (Table 14). Only one sample included yeasts and moulds. Samples 1 and 2: All colonies looked similar. From both of the samples two colonies were microscoped, all of which were rods. Sample 3: The colonies showed full of variety. 11 colonies were microscoped, 9 of which were rods and 2 of which were pediococci. Sample 4: All colonies (2 colonies/sample) were rods. The colonies looked similar to those of control cucumbers. Control: 4 colonies of the control cucumbers were microscoped, all of which were rods. pH, titratable acidity and salt concentration was measured of the cucumber brines. The salt concentration and the titratable acidity were highest in the cucumbers of Producer 1, and lowest in the cucumbers of Producer 2. Of the cucumbers of Producer 3, the cucumbers made with starter had lower pH and higher titratable acidity than the control cucumbers (Figures 3a and 3b). The salt determination showed that salt had been divided evenly to the cucumbers, and the calculatory salt concentration was the same as the result of the titration. The results of the sensory evaluation are collected to Figures 4a and 4b, which show medians of the markings given. The target result of appearance, odor, bitterness and general acceptance was 90, whereas as regards texture, saltiness and acidity the target result was in the middle of the foregoing, 45. The differences between the medians were calculated with SAS-Npair 1 Way program, using the unidirectional non-parametric variance analysis of Kruskall-Wallis. Pairwise comparisons were carried out using variance analysis, and the Wilcoxon Two-Sample test. The cucumbers prepared with the Ferme starter strain mixture were in the practical production experiments found out to be of good quality. The way of preparation, seasoning and salt concentration had effect on the evaluation markings of the cucumbers. The cucumbers of Producer 2 had been fermented for a fairly long time, and their salt concentration was low. This may have caused the excessive softening of the texture. The cucumbers of Producer 1 were evaluated to have best characteristics, although the cucumbers were considered a little two salty. The cucumbers of Producer 3 had no spices, which caused the fact that the cucumbers obtained comments on taste of feed, and stuffyness. The fermented cucumbers of Producer 3 did not differ statistically from the control. The following microorganisms were deposited according to the Budapest Treaty at the DSMZ depositary (Deutsche Sammlung von Mikroorganismen und Zellkulturen, GmbH, Mascheroder Weg 1b, D-38124 Braunschweig, Germany) Eriksson, C. (1991) Lactic acid bacteria and vegetable, cereal, meat and fish fermentations. J. Chem. Tech. Nat. Biotechn. 51:553-556. Gardner, N.J., Savard, T., Obermeier, P., Caldwell, G. and Champagne, C.P. (2001) Selection and characterization of mixed starter cultures for lactic acid fermentation of carrot, cabbage, beet and onion vegetable mixtures. International J. of Food Microbiology 64:261-275. 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(1998) Adhesion of some probiotic and dairy Lactobacillus strains to Caco-2 cell cultures Int. J. Food Microbiol. 41:45 -51. de Valdez, G.F., de Giori, G.S., Garro, M., Mozzi, F. and Oliver, G. (1990) Lactic acid bacteria from naturally fermented vegetables. Microbiologie - Aliments - Nutrition 8:175-179. Ziemer, C.J., and Gibson, G.R. (1998). An overview of probiotics, prebiotics and synbiotics in the functional food concept: perspectives and future strategies. International Dairy Journal, 8:473-479. |
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