Bacterial spores from raw milk that survive the pasteurization process are responsible for half of all the spoilage of fluid milk. Bactofugation has received more attention as a nonthermal method ...that can reduce the presence of bacterial spores in milk and with it the spoilage of fluid milk. The objective of this work was to determine the effectiveness of bactofugation in removing spores from raw milk and estimate the effect the spore removal could have on shelf-life of fluid milk. The study was conducted in a commercial fluid milk processing facility where warm spore removal was performed using one-phase bactofuge followed by warm cream separation and high temperature, short time pasteurization. Samples from different stages of fluid milk processing with and without the use of bactofuge were tested for total plate count, mesophilic spore count, psychrotolerant spore count (PSC), and somatic cell count. Results were evaluated to determine the count reductions during different stages of fluid milk processing and compare counts in fluid milk processed with and without bactofugation. Bactofugation on average reduced the total plate count by 1.81 ± 0.72 log cfu/mL, mesophilic spore count by 1.08 ± 0.71 log cfu/mL, PSC by 0.86 ± 0.59 log cfu/mL, and somatic cell count by 135,881 ± 43,942 cells/mL. Psychrotolerant spore count in final pasteurized skim milk processed with and without bactofugation was used to predict the shelf-life of the pasteurized skim milk using the Monte Carlo simulation model. Although PSC in the initial raw milk was already low (−0.63 ± 0.47 log cfu/mL), the predicted values from the simulation model showed that bactofugation would extend the shelf-life of pasteurized skim milk by approximately 2 d. The results of this study will directly help fluid milk processors evaluate the benefits of using bactofugation as an intervention in their plants, and also demonstrate the benefits of using mathematical modeling in decision making.
Bactofugation is a centrifugal process for removing spores of microorganisms from milk, especially when it is destined for cheese making. Other microorganisms may be removed in bactofugation. This ...study aimed to verify the effect of milk bactofugation on the counts and microbial diversity of psychrotrophs. The raw milk was preheated (≈55°C) before being bactofuged, and samples were collected from 3 batches of milk: refrigerated raw, preheated, and bactofuged, representing the immediate conditions before and after bactofugation. The mean psychrotrophic counts of the 3 batches were 3.08 (±1.69) × 106, 193 (±232), and 20 (±26) cfu/mL, respectively. Preheating was sufficient to eliminate 99.99% of the raw milk psychrotrophs, but bactofugation further reduced 89.66% of psychrotrophs from preheated milk. Lysinibacillus fusiformis was the most frequently isolated species (45.7%) among the psychrotrophs of raw milk and, proportionally, were more frequent in preheated (37.5%) and bactofuged (60%) milk. Bacillus invictae (20%), Enterococcus faecalis (10%), and Kurthia gibsonii (10%) were also isolated from bactofuged milk. Albeit in small numbers, psychrotrophic, thermoduric, and spore-forming bacteria with known proteolytic and lipolytic activity remained in the milk after bactofugation, which apparently had no effect on a specific population of microorganisms but proportionally reduced the entire psychrotrophic microbiota of raw milk.
The objective of this work was to determine the effect of milk bactofugation on the counts and microbial diversity of mesophilic (MT), psychrotrophic (PT), and thermophilic (TT) thermoduric bacteria ...and its potential as a technological method to remove spoilage microorganisms resistant to pasteurization. Different batches of raw milk from 69 dairy farms divided into sets in 3 bulk tanks (A, B, C) were evaluated at different times during the technological process. As the raw milk was preheated (∼55°C) immediately before bactofugation (10,000 × g), the effect of bactofugation was estimated by comparing the counts in raw, preheated, and bactofuged milk. This centrifugation was sufficient to reduce the isolation of 88% of the MT in preheated milk. For PT, it was possible to verify a reduction of 72.5% in batch C. The TT were not recovered at higher detection limits (<5 cfu/mL). For diversity, 310 isolates were identified using a molecular approach; 15 species of contaminating thermoduric bacteria were identified from raw and preheated milk, and only 6 species were recovered in bactofuged milk. Only MT were recovered from the bactofuged milk, mainly the species Lysinibacillus fusiformis (61.7%) and Bacillus licheniformis (12.3%). Both species are known to be endospore-forming psychrotrophs and have proteolytic or lipolytic activity. The bactofugation of raw milk reduced the number of isolates of B. licheniformis, Bacillus toyonensis, Micrococcus aloeverae, and Aestuariimicrobium kwangyangense by 33, 43, 86, and 92%, respectively, and reduced the isolates of Macrococcus caseolyticus, Lysinibacillus varians, Carnobacterium divergens, Microbacterium hominis, Kocuria indica, Micrococcus yunnanensis, Gordonia paraffinivorans, Bacillus invictae, and Kocuria kristinae to undetectable levels. The results of this study indicate that bactofugation can be applied by the dairy industry to reduce pasteurization-resistant microorganisms in combination with prophylactic measures to prevent the contamination of raw milk by spores and vegetative forms of bacteria.
The application of high power ultrasound combined with a slightly increased temperature on raw cow's milk, skimmed cow's milk and skimmed cow's milk that passed the bactofugation process was ...analysed. We combined ultrasound with bactofugation of milk to achieve the microbiological accuracy that is equivalent to pasteurization.
The milk samples (200 mL) were treated for 2.5, 5, 7.5 and 10 min with high-power ultrasound (200 and 400 W) with a frequency of 24 kHz. The treatments were conducted with a constant duty cycle of 100%. Temperatures during the treatments were 20 and 55 °C. The somatic cell count of the aerobic mesophilic bacteria, as well the number of
and
cells were analysed.
From the perspective of the reduction of the total count of bacteria, the best result was achieved by high-power ultrasound at 400 W treated for 10 min. High reduction of
,
and
cells was achieved with ultrasound treatment of raw, skimmed and skimmed cow's milk that passed the bactofugation with a power of 200 and 400 W regardless of the treatment time.
This work combines bactofugation and high-power ultrasound for the inactivation of microoganisms. This combination was used at a slightly increased temperature (up to 55 °C), which is much more economical than pasteurization, while it preserves the sensory and physicochemical properties of milk.
Two methods of milk treatment were used, ultrasound (innovative method) and bactofugation, after which the physicochemical and sensory properties of the milk were examined, with the primary aim of ...achieving the quality and consistency of the pasteurized milk.
Ultrasound power of 200 and 400 W and frequency of 24 kHz with constant wave cycle were used. Milk was treated for 2.5, 5, 7.5 and 10 min with sonification at 20 °C (room temperature) and thermosonification (ultrasound at temperature higher than room temperature) at 55 °C. The purpose of this study is to investigate the effect of high-power ultrasound combined with a slightly increased temperature on whole, skimmed and skimmed cow's milk pretreated with bactofugation.
The best sensory quality was achieved when milk was treated with ultrasound power of 200 W at 20 °C for max. 7.5 min. This research shows the potential of the applications of high-power ultrasound in dairy industry combined with bactofugation as a pre-treatment of milk at a slightly increased temperature (up to 55 °C).
The application of these two treatments requires milder processing conditions than pasteurization, it is economical and more environmentally friendly technological process that preserves better nutritional values of milk, which is preferred by consumers.
In this work the effect of the milk bactofugation and natural whey culture on the microbiological and physicochemical quality of Mozzarella cheese was studied. To this aim, the microbiological, ...sensory and physico-chemical parameters of the Mozzarella cheese were monitored during the storage at 8°C. The bactofugation treatment did not significantly affect the growth of typical dairy microorganisms, while a significant decrease of Enterobacteriaceae in milk was found. The Mozzarella manufactured with natural whey culture and bactofugated milk showed a slower increase in the Pseudomonas spp. cell load during storage. Moreover, the absence of natural whey culture in the Mozzarella cheese manufacture caused a faster sensorial quality loss during storage (~4.5 days) respect to the product with natural starter (~6 days). However, the factor limiting the shelf life of Mozzarella cheese was the growth of Pseudomonas spp. In particular, a shelf life value of about 4.0 days was obtained for Mozzarella produced with bactofugated milk and natural whey culture versus 3.5 days for the control, with citric acidification, and samples manufactured with natural whey culture and no bactofugated milk. The compositional characteristics of the cheeses were influenced by the use of the natural starter, especially at the end of the storage period. In fact, the control cheese tended to lose soluble compounds (WSN and NaCl) faster and, increase in moisture content.
The flavor and quality of the Iranian enzymatic cheese are influenced by different factors during its production and storage. The present study was aimed to investigate the effects of various ...processing conditions, such as pasteurization, retentate treatment, microfiltration (MF), double bactofugation (DBF) and ultrafiltration on the microbial, chemical and textural analysis of the Iranian enzymatic cheese. Our results revealed a significant reduction of the mesophilic bacterial counts (p < 0.05), in all the applied methods of processing. A considerable increase in the numbers of yeasts and molds was observed up to the 21st days of storage (p < 0.05). No obvious changes were observed in the spore counts in 4 °C storage condition, except for the treatment that double bactofugation was excluded. Moreover, the levels of proteins and NPN remained stable. Level of lactose was reduced during the shelfing which was associated with the increased acidity due to the lactose fermentation. In general, the rigidity of samples was gradually increased up to the end of storage (p < 0.05). The current study revealed that concomitant use of different technologies (Hardles’ method) improved the overall acceptance of the cheese and increased its shelf life, the qualities which enhances at 4 °C storage condition.
Conventional technologies for cheese obtaining recommend using pasteurization as a means of destroying pathogenic microorganisms that can cause spoilage of cheese. After pasteurization we add ...lysozyme for prevent blowing in cheeses of low lactic acid content e.g. brined-cheeses such as Gouda. Lysozyme is used in cheese production to prevent "late blowing". This phenomenon is caused by the growth of Clostridium tyrobutyricum, a contaminant present in milk used for cheese production. C. tyrobutyricum ferments the lactate resulting from fermentation of lactose, to produce carbon dioxide, hydrogen, butyric acid and acetic acid. In many cheeses, especially those that are pressed, accumulation of gases during the later stages of curing causes the cheese to "blow", literally to explode. A method by which we can replace the addition of lysozyme is milk bactofugation. This is a process that is based on the differences in specific gravity between milk and microorganisms. Through this process, it aims at reducing the microbial load of milk, eliminating the spores especially because they have a higher specific gravity, without affecting the nutritional value of milk. We determine the microbiological load when using pasteurization, pasteurization in combination with lysozyme and pasteurization in combination with bactofugation. We compare the dates and the technological value of this issue. PUBLICATION ABSTRACT
Pozadina istraživanja. U radu je ispitan postupak obrade sirovog, obranog i baktofugiranog obranog kravljeg mlijeka ultrazvukom velike snage u kombinaciji s blago povišenom temperaturom. Ultrazvuk je ...kombiniran s postupkom baktofugiranja radi postizanja mikrobiološke ispravnosti mlijeka jednake onoj mlijeka obrađenog postupkom pasterizacije.
Eksperimentalni pristup. Uzorci mlijeka (200 mL) tretirani su tijekom 2,5; 5; 7,5 i 10 min ultrazvukom velike snage (200 i 400 W), frekvencije 24 kHz. Tretmani su provedeni s konstantnim valnim ciklusom od 100 %. Temperature tijekom tretmana iznosile su 20 i 55 °C. Analiziran je broj somatskih stanica aerobnih mezofilnih bakterija, kao i broj bakterijskih stanica vrsta Enterobacteriaceae, Escherichia coli i Staphylococcus aureus.
Rezultati i zaključci. Najveće smanjenje ukupnog broja somatskih stanica postignuto je obradom mlijeka ultrazvukom velike snage od 400 W pri trajanju od 10 min. Broj stanica bakterija Enterobacteriaceae, E. coli i S. aureus znatno je smanjen ultrazvučnom obradom sirovog, obranog i baktofugiranog obranog kravljeg mlijeka pri snazi od 200 i 400 W, neovisno o trajanju postupka.
Novina i znanstveni doprinos. U radu su primijenjene dvije tehnologije, baktofugiranje i ultrazvuk velike snage, kako bi se u većoj mjeri inaktivirali mikroorganizmi u kravljem mlijeku. Kombinacija ova dva postupka obrade pri blago povišenoj temperaturi (55 °C) je puno ekonomičnija od procesa pasterizacije, a pritom su bolje očuvana senzorska i fizikalno-kemijska svojstva mlijeka.
Pozadina istraživanja. Primjenjene su dvije metode obrade mlijeka: ultrazvuk (inovativna metoda) i baktofugiranje, nakon čega su ispitana fizikalno-kemijska i senzorska svojstva mlijeka, s osnovnom ...svrhom postizanja kakvoće i konzistencije pasteriziranog mlijeka.
Eksperimentalni pristup. Korištena je snaga ultrazvuka od 200 i 400 W pri frekvenciji od 24 kHz s konstantnim valnim ciklusom. Mlijeko je tretirano sonifikacijom tijekom 2,5; 5; 7,5 i 10 min na 20 °C (sobnoj temperaturi) i termosonifikacijom (primjenom ultrazvuka na temperaturi višoj od sobne temperature) na 55 °C. Svrha je ove studije bila istražiti učinak ultrazvuka velike snage u kombinaciji s djelomično povišenom temperaturom na sirovo punomasno, obrano i obrano kravlje mlijeko prethodno obrađeno baktofugiranjem.
Rezultati i zaključci. Najbolja senzorska kakvoća postignuta je obradom mlijeka ultrazvukom snage od 200 W pri 20 °C, tijekom maksimalno 7,5 min. Ovo istraživanje pokazuje potencijal primjene ultrazvuka velike snage u mljekarskoj industriji u kombinaciji s baktofugiranjem kao postupkom prethodne obrade mlijeka na djelomično povišenoj temperaturi (do 55 °C).
Novina i znanstveni doprinos. Tijekom primjene ova dva postupka prerade mlijeka koriste se blaži uvjeti obrade od pasterizacije, pa se mogu smatrati ekonomičnim i ekološki prihvatljivijim tehnološkim postupcima, pomoću kojih se može bolje očuvati hranjiva vrijednost mlijeka, a što preferiraju i potrošači.
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