Bacteriocin-producing lactococci were isolated from raw ewes’ milk samples obtained from 5 different Protected Designation of Origin Zamorano cheese manufacturers. Thirteen isolates with ...antimicrobial activity against Lactococcus lactis HP were selected. Eleven were identified by a PCR technique as L. lactis ssp. lactis and 2 were identified as L. lactis ssp. cremoris. They were grouped under 4 different pulsed-field gel electrophoresis patterns. The presence of structural genes of both nisin and lacticin 481 was detected in 10 L. lactis ssp. lactis isolates belonging to 2 different pulsed-field gel electrophoresis patterns. Coproduction of nisin and lacticin 481 was confirmed after semipurification by using selective indicators. The production of 2 bacteriocins by the same strain is an uncommon property, with relevance in food safety. Nisin and lacticin 481 L. lactis-producing strains might be used as adjunct cultures to the commercial starter in the manufacture of dairy products.
Raw milk from 13 cows fed TMR supplemented with native pasture and from 13 cows fed only TMR on one farm was collected separately 4 times with an interval of 15 d between collections. Two blocks ...(14kg each) of cheese were made from each milk. The objective was to determine the influence of consumption of native plants in Sicilian pastures on the aroma compounds present in Ragusano cheese. Milk from cows that consumed native pasture plants produced cheeses with more odor-active compounds. In 4-mo-old cheese made from milk of pasture-fed cows, 27 odor-active compounds were identified, whereas only 13 were detected in cheese made from milk of total mixed ration-fed cows. The pasture cheeses were much more rich in odor-active aldehyde, ester, and terpenoid compounds than cheeses from cows fed only total mixed ration. A total of 8 unique aroma-active compounds (i.e., not reported in other cheeses evaluated by gas chromatography olfactory) were detected in Ragusano cheese made from milk from cows consuming native Sicilian pasture plants. These compounds were 2 aldehydes (E,E-2,4-octadienal and dodecanal), 2 esters (geranyl acetate and E-methyl jasmonate), 1 sulfur compound (methionol), and 3 terpenoid compounds (1-carvone, L(-) carvone, and citronellol). Geranyl acetate and (E)-methyl jasmonate were particularly interesting because these compounds are released from fresh plants as they are being damaged and are part of a possible plant defense mechanism against damage from insects. Most of the odor-active compounds that were unique in Ragusano cheese from pasture-fed cows appeared to be compounds created by oxidation processes in the plants that may have occurred during foraging and ingestion by the cow. Some odor-active compounds were consistently present in pasture cheeses that were not detected in the total mixed ration cheeses or in the 14 species of pasture plants analyzed. Either these compounds were present in other plants not analyzed, created in the rumen or in cheese after the pasture-plant material had been consumed, or the compounds were lost in the method of sample extraction used for the plant analysis (i.e., steam distillation) versus the solid-phase microextraction method used for the cheeses. This research has demonstrated clearly that some unique odor-active compounds found in pasture plants can be transferred to the cheese.
Electronic nose presents a rapid method to determine quality characteristics of foodstuffs. Ion mobility spectrometry allows rapid and simple on-site determination of gaseous compounds. Ion mobility ...based electronic nose system “MGD-1” was used to determine the separation of various hard and extra-hard cheese samples via headspace analysis. The verification of the electronic nose system was performed for different applications such as the discrimination of Emmental cheeses based on either age or geographical origin, and the discrimination of different cheeses based on variety. Nine month ripened Emmental cheeses were successfully discriminated from Emmental cheeses with 3 or 6 month ripening time. The results obtained from Emmental cheeses and other hard and extra-hard cheese varieties showed that the MGD-1 system is of a significant potential for discrimination of the cheese samples.
The microbial communities present in 2 different types of farmhouse goats' milk cheese from the Aracena mountains (southwest Spain), Quesailla Arochena (hard cheese) and Torta Arochena (soft cheese), ...have been studied using both culture-dependent and culture-independent techniques. All bacterial isolates were clustered by using randomly amplified polymorphic DNA (RAPD) and identified by 16S rRNA gene sequencing, species-specific PCR and multiplex PCR. Thus a total of 26 different species were identified, the majority belonging to the lactic-acid bacteria (LAB), mainly represented by
Lactococcus lactis and
Lactobacillus species such as
Lactobacillus plantarum and
Lactobacillus paracasei, together with a significant proportion of enterococci. Amongst the non-lactic-acid bacteria (NLAB), which represented 37% of the isolates in Torta Arochena, enterobacteria were the most important,
Hafnia alvei and
Serratia liquefaciens being the predominant species in Quesailla Arochena and Torta Arochena respectively. Moreover, RAPD analysis of the isolates revealed that most of the genotypes were specific to one of the cheeses, although a few genotypes common to both cheeses were found.
The culture-independent study carried out by temporal-temperature-gradient gel electrophoresis (TTGE) with 2 target genes, rRNA 16S and
rpoB, revealed less species diversity but
L. lactis and
Lb. plantarum were also predominant. Nevertheless, TTGE carried out using RNAr 16S also detected some organisms that had not been isolated by the culture-dependent method, such as
Leuconostoc lactis and
Mycoplasma agalactie in Quesailla Arochena. Although TTGE of the
rpoB gene revealed less species diversity, it did lead to the detection of previously non-isolated species, such as
Ln. lactis in Quesailla Arochena. Apart from this, the fingerprinting of
Lactobacillus populations by length-heterogeneity PCR showed the predominance of the
Lb. plantarum group, followed by
Lactobacillus curvatus and, in smaller quantities,
Lb. paracasei in Torta Arochena. From our results we may conclude that both types of methods complement each other and offer a more complete vision of the microbial diversity of these ecosystems.
A near-infrared spectroscopy (NIRS) application was developed to discriminate Asiago d’Allevo cheese coming from different production chains (alpine farms, mountain and lowland factories). One ...hundred wheels were collected in different seasons from all productive sites of Asiago d’Allevo: 14 alpine farms and 8 mountain and 13 lowland factories. Samples were analyzed for chemical composition and color and scanned by NIRS (1100−2500 nm). A factorial discriminant analysis based on chemical and color data showed a clear separation between alpine and factory products due to their different fatty acids profile and color. However, cheeses from lowland and mountain factories were undistinguishable. A discriminant analysis using NIRS spectra alone or combined with chemical and color data showed similar results. A final calibration based on NIRS spectra was developed and validated by a set of 7 external samples to discriminate alpine from factory products. This real-time analysis is a reliable alternative to expensive and time-consuming lab determinations.
Content of biogenic amines (BA; histamine, tyramine, tryptamine, putrescine, 2-phenylethylamine, cadaverine, spermidine, spermine) and counts of microorganisms (total aerobic and facultative ...anaerobic mesophilic microorganisms, TAC; lactic acid bacteria, LAB; coliforms; total anaerobic microorganisms, TAN; yeasts
+
moulds), were evaluated within the ripening interval of 1–6 months in Dutch-type hard cheese, produced by two different producers (the cheeses designated as R30 and R45) using pasteurized milk and different starter cultures (designated as R30-FD and R30-CH in the case of the R30 cheeses). The cheeses from the two producers differed in their fat content (30% and 45% of fat in dry matter, respectively).
Substantially higher (
P
<
0.01) contents of tyramine and the sum of biogenic amines were found in the outer-part samples in comparison with the core ones in the R30 cheeses, which corresponded with higher (
P
<
0.01) TAN counts in this part of the cheese with presumably more favourable growth conditions.
Tyramine content increased linearly (
P
<
0.01) with increasing time of ripening both in R30-FD and R30-CH and R45 cheese, and concentration of this BA in the R45 cheese after 18 weeks of ripening (309.5
mg
kg
−1) exceeded a toxicological limit. Also putrescine content and sum of all BA increased significantly (
P
<
0.001) in all cheeses within the ripening interval.
Tyramine, putrescine and phenylethylamine contents, and sum of all biogenic amines and sum of polyamines in R45 cheese (299.8, 60.8, 54.3, 419.0 and 63.2
mg
kg
−1 of the fresh matter, respectively) were significantly higher (
P
<
0.01) after 22nd week of ripening in comparison with both R30 cheeses (15.7–41.2, 6.0–6.7, 1.0–2.0, 36.4–68.3 and 7.1–7.5
mg
kg
−1, respectively). However, TAC, TAN and LAB counts tended to be higher (
P
>
0.05) in R30-FD and R30-CH samples than in R45 cheeses in this time interval. The microbiological analysis based only on basic groups of microorganisms was inconclusive regarding differences in BA content in the cheeses.
Edible gums were evaluated for folic acid encapsulation efficiency as single and mixed polymers. Alginate and pectin yielded the highest encapsulation efficiencies, 216 and 196
μg/100
g, ...respectively. Upon being combined and the encapsulation conditions optimized, the alginate–pectin (alg–pect) mixture resulted in 360
μg/100
g of folic acid being encapsulated. The alg–pect capsules were tested for their stability in a milk system where pH was adjusted from 6.7 to 4.5 over a 4
h period. Folic acid retention under the test conditions was retained at 360
μg/100
g within the alg–pect capsules indicating their ability to remain intact in a milk system. Stress tolerance of the capsules was tested under simulated cheese press pressures for 4
h until a force of 0.814
N/cm
2 was detected. Folic acid retention of up to 288
μg/100
g was recorded for the alg–pect capsules. Three stages in Cheddar cheese manufacturing namely; addition of capsules in the milk, incorporation of capsules after milling the curd and injection into the pressed block of raw cheese, were studied for capsules distribution. The former had the most even distribution of capsules while the latter two had poor and irregular distribution. Encapsulated folic acid showed more stability (360
μg/100
g) than the free folic acid (109
μg/100
g) in Cheddar cheese during the 3 months ripening period.
Extra hard cheese is commonly made with thermophilic starters using high temperatures to stimulate expulsion of whey. In this work, microflora, proteolysis and volatiles were investigated in an ...extra-hard cheese made with mesophilic DL-starter, produced using challenging cooking temperatures for the starter bacteria over several hours. Cheese from six commercially produced vats was investigated over 56 weeks. The number of starter bacteria decreased after three weeks of ripening. Casein breakdown was characterised by chymosin and plasmin activity on α
s1- and β-caseins, respectively. Peptide profiles showed accumulation of
Lactococcus derived peptides from α
s1-CN f1–23, and the peptide β-CN 29–93 as a result of joint plasmin and chymosin activity and absence of highly proteolytic thermophilic
Lactobacillus, commonly present in extra-hard cheese. The composition of amino acids depended mainly on starter during the first 26 weeks of ripening. The content of volatiles depended both on ripening time and the starter used.
The cell-envelope-associated proteinase of Lactobacillus delbrueckii subsp. lactis CRL 581 (PrtL) has an essential role in bacterial growth and contributes to the development of the organoleptic ...properties of hard cheeses and to the release of bioactive health-beneficial peptides from milk proteins. In this study, the effect of environmental pH on PrtL production by L. delbrueckii subsp. lactis CRL 581 in a chemically defined medium and the influence of pH, temperature, and Ca2+ ions on PrtL activity, stability, and release from the cell envelope were analyzed. The maximum PrtL activity levels were observed in the middle of the exponential growth phase, with the values at constant pH of 5.5 and 6.0 being higher than those observed at pH 4.5 and 5.0. At pH 4.5, PrtL remained mainly associated with the cell envelope, whereas at pH values of 5.5 or higher, approximately 40% of PrtL was found in the medium. In addition, the PrtL activity was stable for 24 h at 4 and 25 °C, and its release at 4, 25, and 40 °C was time-dependent. PrtL activity, stability, and release were independent of the presence of Ca2+ ions in the medium. These results indicated that, at pH and temperature conditions found during the manufacture of hard cheeses, PrtL would remain active either bound to the cell or released in the supernatant contributing to the organoleptic characteristics and beneficial health effects of the fermented milk products.
Grated Graviera cheese was stored for up to 9 weeks under both fluorescent light and in the dark, packaged aerobically and under modified atmosphere packaging (MAP) of (a) 100% CO
2, (b) 100% N
2 and ...(c) 50% CO
2/50% N
2. Cheese samples stored under fluorescent light showed a higher degree of lipid oxidation (
P
<
0.05) (ca. 3–4 times higher for MAP samples and 20 times higher for aerobically packaged samples) and suffered a gradual discolouration compared with samples stored in the dark. Chemical composition did not produce statistically significant changes (
P
>
0.05) as a function of storage time. Solid phase microextraction–gas chromatography/mass spectroscopy was used to determine volatile compounds produced under specific packaging treatments. Free fatty acids, esters, aldehydes, ketones and alcohols were recorded for all treatments, with aerobic packaging and exposure to light giving higher concentrations of volatile compounds compared with other treatments. Sensory analysis showed that light, gas composition and storage time significantly affected (
P
<
0.05) taste and odour attributes of grated Graviera cheese. The best sensory attributes were obtained using 100% N
2 or 50% N
2/50% CO
2 and storage in the dark. That is, samples packaged in either 100% N
2 or 50% N
2/50% CO
2 retained acceptable taste for 9 weeks stored in the dark vs. 4 weeks under light. For aerobically packaged samples, respective shelf life was 2.5 weeks vs. 2 weeks.
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