Adjunct Starter Cultures Research Articles

Genotypic and technological diversity of Brevibacterium linens strains for use as adjunct starter cultures in 'Pecorino di Filiano' cheese ripened in two different environments.

Twenty-two Brevibacterium linens strains isolated from 'Pecorino di Filiano' cheese ripened in two different environments (natural cave and storeroom) were characterized and differentiated for features of technological interest and by genotypic methods, in order to select strains with specific features to be used as surface starter cultures. Results showed significant differences among strains on the basis of physiological and technological features, indicating heterogeneity within the species. A middle-low level of proteolytic activity was observed in 27.3% of strains, while a small group (9.1%) showed a high ability. Lipolytic activity was observed at three different temperatures and the highest value was detected at 20°C with 13.6% of strains, while an increase in temperature produced a slightly lower lipolysis in all strains. The evaluation of diacetyl production revealed that only 22.8% of strains showed this ability, and most of them were isolated from product ripened in the natural cave. All strains exhibited only leu-aminopeptidase activity, with values more elevated in strains coming from the natural cave product. The combined analysis of genotypic results with the data obtained by the features of technological interest study established that the random amplified polymorphic DNA (RAPD) clusters obtained were composed not only of different genotypes but of different profiles based on technological properties too. This study demonstrated the importance of the ripening environment that affects the typical features of the artisanal product, leading to the selection of a specific surface microflora. Characterized strains could be associated within surface starters to standardize the production process of cheese, but preserving its typical organoleptic and sensory characteristics and improving the quality of the final product.

Genotypic and technological diversity of Leuconostoc mesenteroides and Lactobacillus paracasei subsp. paracasei strains for use as adjunct starter cultures in Pecorino di Filiano cheese

Seventeen Leuconostoc mesenteroides and 33 Lactobacillus paracasei subsp. paracasei from traditional Pecorino di Filiano cheese were tested for their potential use as adjunct starters, and a study of their genetic variability was carried out. Forty one per cent (41%) of Leu. mesenteroides and 46% of Lb. paracasei subsp. paracasei showed medium–high proteolytic activity, while high lipolytic activity was detected in 18% of Lb. paracasei subsp. paracasei. The aminopeptidase activity of Lb. paracasei subsp. paracasei was higher than that of Leu. mesenteroides. Strain diversity by RAPD analysis showed a high degree of heterogeneity. This study identified strains with unusual properties that could be good candidates as adjuncts in a starter to manufacture PF cheese.

Production of propionic acid in a fermented dairy beverage

A dairy beverage containing propionic acid was produced using the adjunct starter cultures with Lactobacillus acidophilus and Propionibacterium freudenreichii ssp. shermanii. The impacts of temperature (30, 35 and 40 °C) and inoculation ratio (1:2, 1:4 and 1:8) on propionic acid production and viability of micro‐organisms were studied. The incubation temperature had a significant adverse (P < 0.05) effect on the viability of P. freudenreichii and propionic acid production. Maximum amount of produced propionic acid (in 1:4–30 °C treatment) was 0.77%w/w. P. freudenreichii and L. acidophilus counts remained high (9 × 106 and 1.5 × 106 cfu/mL, respectively) after cold storage.

Yeasts from Colombian Kumis as source of peptides with Angiotensin I converting enzyme (ACE) inhibitory activity in milk

This study investigated the possibility of using yeast strains in fermented milks to obtain products with high Angiotensin I-converting enzyme (ACE) inhibitory activity and low bitter taste. Ninety‐three yeast strains isolated from Colombian Kumis in different geographic regions were molecularly identified, and their milk fermentation performances were determined. Molecular identification evidenced that Galactomyces geotrichum, Pichia kudriavzevii, Clavispora lusitaniae and Candida tropicalis, were the dominant species. Eighteen out of 93 strains produced fermented milk with ACE-inhibitory (ACEI) activity values ranging from 8.69 to 88.19%. Digestion of fermented milk samples by pepsin and pancreatin demonstrated an increase in ACEI activity, with C. lusitaniae KL4A as the best producer of ACEI peptides. Moreover, sensory analysis of the products containing the major ACE-inhibitory activity pointed out that P. kudriavzevii KL84A and Kluyveromyces marxianus KL26A could be selected as potential adjunct starter cultures in Kumis, since they made a considerable contribution to the ACE inhibitory activity and produced fermented milk without bitter taste. In this study we observed that Colombian Kumis can be an excellent vehicle for the isolation of yeasts with a potential to enhance bioactive peptides produced during milk fermentation.

Effects of different adjunct starter cultures on proteolysis of reduced fat Cheddar cheese during ripening

Effects of different adjunct starter cultures on proteolysis of reduced fat Cheddar cheese during ripening

Effects of different adjunct starter cultures on proteolysis of reduced fat Cheddar cheese during ripening

The evolution of non-protein-nitrogen (NPN), total and free amino acids in reduced fat Cheddar cheese, prepared by formulated milk for Cheddar cheese with optimized texture, using a single and mixture of adjunct starter cultures during storage was studied. The concentrations of NPN, free and total amino acids were significantly affected by the type of microorganism present and the storage time. The total concentration of free amino acids (TFAA) and NPN in reduced fat cheeses inoculated with adjunct starter culture were higher than full fat control cheese without any adjunct starter culture. Also, higher level of TFAA and NPN were observed in reduced fat cheeses made with single culture of Lactobacillus helveticus. The concentration of glutamine, methionine and leucine as major precursors and contributors to sapid taste and flavor compound in reduced fat cheeses made with single culture of L. helveticus were higher than reduced fat Cheddar cheeses inoculated withLactobacillus casei and Streptococcus thermophilus, and even higher than full fat control cheese made with usual mesophilic starter culture. Key words: Cheddar cheese, amino acid, non-protein-nitrogen, adjunct starter culture, xanthan gum.

New insights into the citrate metabolism of Enterococcus faecium FAIR-E 198 and its possible impact on the production of fermented dairy products

Citrate metabolism by Enterococcus faecium FAIR-E 198, an isolate from Greek Feta cheese, was studied in milk-based media compared with modified de Man–Rogosa–Sharpe (mMRS) medium. Co-metabolism of lactose and citrate was shown. The presence of fermentable lactose and glucose in mMRS medium under microaerophilic conditions increased the yield of acetate from citrate conversion but decreased the yield of acetoin compared with a fermentation in the presence of non-fermentable xylose. Under anaerobic conditions in mMRS medium, the yield of ethanol based on citrate increased and diacetyl was no longer found. In milk medium, additional nitrogen sources (e.g., casitone) were necessary to sustain co-metabolism of citrate and lactose. Addition of extra citrate to milk-based medium did not affect citrate conversion, although a lower yield of acetate was found. As citrate conversion was associated with the stationary growth phase, E. faecium FAIR-E 198 is an interesting adjunct starter culture for cheese ripening.

A high-throughput cheese manufacturing model for effective cheese starter culture screening

Cheese making is a process in which enzymatic coagulation of milk is followed by protein separation, carbohydrate removal, and an extended bacterial fermentation. The number of variables in this complex process that influence cheese quality is so large that the developments of new manufacturing protocols are cumbersome. To reduce screening costs, several models have been developed to miniaturize the cheese manufacturing process. However, these models are not able to accommodate the throughputs required for systematic screening programs. Here, we describe a protocol that allows the parallel manufacturing of approximately 600 cheeses in individual cheese vats each with individual process specifications. Protocols for the production of miniaturized Gouda- and Cheddar-type cheeses have been developed. Starting with as little as 1.7mL of milk, miniature cheeses of about 170mg can be produced and they closely resemble conventionally produced cheese in terms of acidification profiles, moisture and salt contents, proteolysis, flavor profiles, and microstructure. Flavor profiling of miniature cheeses manufactured with and without mixed-strain adjunct starter cultures allowed the distinguishing of the different cheeses. Moreover, single-strain adjunct starter cultures engineered to overexpress important flavor-related enzymes revealed effects similar to those described in industrial cheese. Benchmarking against industrial cheese produced from the same raw materials established a good correlation between their proteolytic degradation products and their flavor profiles. These miniature cheeses, referred to as microcheeses, open new possibilities to study many aspects of cheese production, which will not only accelerate product development but also allow a more systematic approach to investigate the complex biochemistry and microbiology of cheese making.

Comparative genomic analysis of Lactobacillus rhamnosus GG reveals pili containing a human- mucus binding protein

To unravel the biological function of the widely used probiotic bacterium Lactobacillus rhamnosus GG, we compared its 3.0-Mbp genome sequence with the similarly sized genome of L. rhamnosus LC705, an adjunct starter culture exhibiting reduced binding to mucus. Both genomes demonstrated high sequence identity and synteny. However, for both strains, genomic islands, 5 in GG and 4 in LC705, punctuated the colinearity. A significant number of strain-specific genes were predicted in these islands (80 in GG and 72 in LC705). The GG-specific islands included genes coding for bacteriophage components, sugar metabolism and transport, and exopolysaccharide biosynthesis. One island only found in L. rhamnosus GG contained genes for 3 secreted LPXTG-like pilins (spaCBA) and a pilin-dedicated sortase. Using anti-SpaC antibodies, the physical presence of cell wall-bound pili was confirmed by immunoblotting. Immunogold electron microscopy showed that the SpaC pilin is located at the pilus tip but also sporadically throughout the structure. Moreover, the adherence of strain GG to human intestinal mucus was blocked by SpaC antiserum and abolished in a mutant carrying an inactivated spaC gene. Similarly, binding to mucus was demonstrated for the purified SpaC protein. We conclude that the presence of SpaC is essential for the mucus interaction of L. rhamnosus GG and likely explains its ability to persist in the human intestinal tract longer than LC705 during an intervention trial. The presence of mucus-binding pili on the surface of a nonpathogenic Gram-positive bacterial strain reveals a previously undescribed mechanism for the interaction of selected probiotic lactobacilli with host tissues.

AROMATIC CHARACTERISTICS OF PECORINO CHEESES OBTAINED FROM MILK OF EWES FED DIETS CONTAINING DIFFERENT EXTRUDED LINSEED CONCENTRATIONS

The aim of the present study is to investigate the flavour characteristics of ewe cheeses made with two different techniques (cheeses obtained from raw milk or from thermized milk with adjunct starter cultures) and using milk from animals fed diets with different concentrations of extruded linseed. Aromatic differences linked to the linseed concentrations in the diets were found for the raw milk cheeses, while no such differences were found in the cheeses made from thermized milk with adjunct starter cultures.

AROMATIC CHARACTERISTICS OF PECORINO CHEESES OBTAINED FROM MILK OF EWES FED DIETS CONTAINING DIFFERENT EXTRUDED LINSEED CONCENTRATIONS

The aim of the present study is to investigate the flavour characteristics of ewe cheeses made with two different techniques (cheeses obtained from raw milk or from thermized milk with adjunct starter cultures) and using milk from animals fed diets with different concentrations of extruded linseed. Aromatic differences linked to the linseed concentrations in the diets were found for the raw milk cheeses, while no such differences were found in the cheeses made from thermized milk with adjunct starter cultures.

Technological characterization of Lactobacillus isolates from traditional Manchego cheese for potential use as adjunct starter cultures

Thirty Lactobacillus isolates from artisanal Manchego cheeses, 10 belonging to Lactobacillus plantarum and 20 belonging to Lactobacillus paracasei subsp. paracasei, were examined for potential use as adjunct cultures. Isolates were screened for acidifying and amino-biogenic capacity, for proteolytic, lipolytic, autolytic and aminopeptidase activities, and for sensory characteristics in UHT coagulated milk. Most of the lactobacilli displayed high aminopeptidase and autolytic activities and low acidifying activity. Only one isolate was able to produce tyramine. When growing on milk 53.3% of the Lb. paracasei subsp. paracasei isolates were able to produce pleasant flavours. Strains PBL210 ( Lb. plantarum) and PBL213 and PBL226 ( Lb. paracasei subsp. paracasei) presented the best technological characteristics, and also were still viable and with unaltered properties after freeze-drying and storage for 12 months. For these reasons, these strains could be good candidates for inclusion as adjuncts in a starter culture to manufacture industrial Manchego cheese.

Effect of Using Propionic Acid Bacteria as an Adjunct Culture in Yogurt Production

Propionibacteria are able to produce a wide variety of food components beneficial to human health. In this study, yogurt was produced by using the adjunct starter cultures Propionibacterium jensenii B1264 and Propionibacterium thoenii (jensenii) P126. Although the total solids and protein contents of the yogurts did not show any significant differences, titratable acidity of the control sample (YC-380) remained lower than that of Propionibacterium spp.-supplemented yogurts during 15 d of storage. The yogurts produced by YC-380+P126 cultures had the firmest structure (0.26N). The highest acetaldehyde (29.35 mg/kg) content was obtained with yogurt made with YC-380+P126+B1264 on d 1. The addition of propionibacteria to yogurt did not have any negative effect on the counts of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus in yogurt. During the first week of storage, propionibacteria counts remained high, suggesting that yogurt provided a good environment for these organisms. This new product would provide not only beneficial health effects, but also a new alternative product to plain set-type yogurt.

Effect of Enterococcus faecium on microbiological, physicochemical and sensory characteristics of Greek Feta cheese

Greek Feta cheese was prepared using as adjunct starter cultures Enterococcus faecium FAIR-E 198, E. faecium FAIR-E 243, and their combination. Numbers of enterococci in the control and in the batches containing E. faecium strains as adjunct starters rapidly increased until day 15 of ripening, and then remained constant. Both E. faecium strains positively affected the counts of non-starter lactic acid bacteria (NSLAB), micrococci and coliforms, while thermophilic cocci were not influenced. Moreover, E. faecium FAIR-E 243 enhanced the growth of mesophilic cocci and thermophilic bacilli. Physicochemical characteristics, such as pH, moisture, ash, salt in moisture and fat in dry matter (FDM) were not influenced by the addition of the E. faecium strains. The most pronounced effect was observed in the case of proteolysis. Both E. faecium strains, either as sole adjunct starter or in combination, increased the proteolytic index and the free amino groups concentration, and enhanced degradation of α s1- and β-caseins in comparison to the control. Furthermore, the reverse-phase (RP)-HPLC peptide profiles of the water-soluble nitrogen (WSN) fractions were significantly affected by the addition of enterococci. The main volatile compounds produced were ethanol, acetate, acetone, acetaldehyde, acetoin and diacetyl, with highest amounts determined for ethanol, followed by acetate. Both E. faecium strains positively affected taste, aroma, colour and structure of the full-ripened cheeses, as well as the overall sensory profile. The present work emphasizes the technological significance of E. faecium strains and supports their use as adjunct cultures in the manufacture of Feta cheese.