Analysis of variables that influence microbiological quality in fresh cheese production

U radu su ispitivane varijable koje utječu na mikrobiološku kvalitetu u proizvodnji svježeg sira s obzirom na kvasce i plijesni. Kvasci i plijesni ne preživljavaju pasterizaciju, a izolirani iz gotovog proizvoda posljedica su naknadne kontaminacije tijekom fermentacije mlijeka i izdvajanja sirutke. Stoga su u ovom radu mjerene sljedeće varijable: ukupni broj aerobnih mezofilnih bakterija u ispirnoj vodi, ukupni broj kvasaca i plijesni u ispirnoj vodi, ukupni broj aerobnih mezofilnih bakterija u pasteriziranom mlijeku za sirenje, ukupni broj aerobnih mezofilnih bakterija u zraku i ukupni broj kvasaca i plijesni u zraku. Navedene varijable analizirane su pomoću statističkih metoda deskriptivne statistike i metode glavnih komponenata (PCA), te metode umjetne inteligencije, stabla odlučivanja. Rezultati metode glavnih komponenata, s obzirom na broj kvasaca i plijesni u gramu svježeg sira, pokazali su da najveći utjecaj na kvalitetu sira ima mikrobiološka čistoća zraka. Pomoću metode stabla odlučivanja dobiveni su interni standardi za ukupan broj aerobnih mezofilnih bakterija te kvasaca i plijesni u zraku koji utječu na mikrobiološku kvalitetu svježeg sira.In this research variables which influence microbiological quality in fresh cheese productionwith respect to yeasts and moulds were analyzed. Since yeasts and moulds do not survive the process of pasteurization their isolation in the final product is a result of their supplemental contamination during fermentation and whey drainage. Following variables were monitored: total number of aerobic mesophilic bacteria AMB in rinsing water, total number of yeasts and moulds in rinsing water, total number of AMB in pasteurized milk, total number of AMB in air and total number of yeasts and moulds in air. These variables were analysed by methods of descriptive statistics, principal component analysis, and the method of artificial intelligence - decision tree. By the method of principal component analysis it is shown that the greatest impact on the quality of the final product have variables connected to microbiological cleanness of air. The method of decision tree has resulted in determination of new internal standards for total number of AMB and yeasts and moulds in the air

Analysis of variables that influence microbiological quality in fresh cheese production

U radu su ispitivane varijable koje utječu na mikrobiološku kvalitetu u proizvodnji svježeg sira s obzirom na kvasce i plijesni. Kvasci i plijesni ne preživljavaju pasterizaciju, a izolirani iz gotovog proizvoda posljedica su naknadne kontaminacije tijekom fermentacije mlijeka i izdvajanja sirutke. Stoga su u ovom radu mjerene sljedeće varijable: ukupni broj aerobnih mezofilnih bakterija u ispirnoj vodi, ukupni broj kvasaca i plijesni u ispirnoj vodi, ukupni broj aerobnih mezofilnih bakterija u pasteriziranom mlijeku za sirenje, ukupni broj aerobnih mezofilnih bakterija u zraku i ukupni broj kvasaca i plijesni u zraku. Navedene varijable analizirane su pomoću statističkih metoda deskriptivne statistike i metode glavnih komponenata (PCA), te metode umjetne inteligencije, stabla odlučivanja. Rezultati metode glavnih komponenata, s obzirom na broj kvasaca i plijesni u gramu svježeg sira, pokazali su da najveći utjecaj na kvalitetu sira ima mikrobiološka čistoća zraka. Pomoću metode stabla odlučivanja dobiveni su interni standardi za ukupan broj aerobnih mezofilnih bakterija te kvasaca i plijesni u zraku koji utječu na mikrobiološku kvalitetu svježeg sira.In this research variables which influence microbiological quality in fresh cheese productionwith respect to yeasts and moulds were analyzed. Since yeasts and moulds do not survive the process of pasteurization their isolation in the final product is a result of their supplemental contamination during fermentation and whey drainage. Following variables were monitored: total number of aerobic mesophilic bacteria AMB in rinsing water, total number of yeasts and moulds in rinsing water, total number of AMB in pasteurized milk, total number of AMB in air and total number of yeasts and moulds in air. These variables were analysed by methods of descriptive statistics, principal component analysis, and the method of artificial intelligence - decision tree. By the method of principal component analysis it is shown that the greatest impact on the quality of the final product have variables connected to microbiological cleanness of air. The method of decision tree has resulted in determination of new internal standards for total number of AMB and yeasts and moulds in the air

Inaktivacija Enterobakterija u mlijeku ultrazvukom visokog intenziteta

Ultrasonication is a non-thermal method of food preservation that has the advantage of inactivating microbes in food without causing the common side-effects associated with conventional heat treatments, such as nutrient and flavour loss. In this work high intensity ultrasound was used to investigate inactivation Enterobacteriae count in raw milk. Raw milk with 4% of milk fat was treated with ultrasonic probe that was 12 mm in diameter and with 20 kHz frequency immerged in milk directly. For ultrasounds treatment, three parameters varied according to the statistical experimental design. Centre composite design was used to optimize and design experimental parameters: temperature (20, 40 and 60 °C), amplitude (120, 90 and 60 μm) and time (6, 9 and 12 minutes). All analyses were performed immediately after sonication and after 3 and 5 days of storage in refrigeration at 4 °C. The facts that substantially affect the inactivation of microorganisms using ultrasound are the amplitude of the ultrasonic waves, the exposure/contact time with the microorganisms, and the temperature of treatment. The achieved results indicate significant inactivation of microorganisms under longer period of treatments with ultrasonic probe particularly in combination with higher temperature and amplitude. Output optimal value of Enterobacteriae count has been defined by Statgraphics where lowest Enterobacteriae count (1.06151 log CFU mL-1) was as follows for specific ultrasound parameters: amplitude of 120 μm, treatment time for 12 min and temperature of 60 °C.Ultrazvuk kao netermalna metoda procesiranja hrane ima svoje prednosti pri inaktivaciji mikroorganizama u hrani u odnosu na klasične metode procesiranja hrane budući da uzrokuje manje negativnih učinaka npr. gubitak važnih nutrijenata te aroma. U ovom radu ispitivana je inaktivacija Enterobakterija u mlijeku primjenom ultrazvuka visokog intenziteta. Sirovo mlijeko sadržaja masti 4 %, tretirano je ultrazvučnom sondom promjera 12 mm i frekvencije 20 kHz. Eksperiment je planiran i proveden koristeći kompjuterski program STATGRAFICS (Centre composite design - CCD). Ultrazvučna obrada provedena je prateći tri parametra - temperaturu (20, 40 i 60 °C), amplitudu (120, 90 i 60 μm) te vrijeme procesiranja (6, 9 i 12 minuta). Sve analize provedene su neposredno nakon sonificiranja te nakon 3 odnosno 5 dana skladištenja uzoraka u hladnjaku na temperaturi od 4 °C. Inaktivirajući učinak ultrazvuka na mikroorganizme (Enterobakterije) ovisio je o primijenjenoj amplitudi ultrazvuka, vremenu i temperaturi procesiranja mlijeka. Dobiveni rezultati pokazuju značajan inaktivirajući učinak ultrazvuka kod dužeg perioda obrade ultrazvučnom sondom u kombinaciji sa povišenom temperaturom i amplitudom od 120 μm. Optimalna vrijednost (najmanja) Enterobakterija (1,06151 log cfu mL-1) u mlijeku određena je Statgraphics-om pri sljedećim uvjetima obrade ultrazvukom: amplituda 120 μm, vrijeme obrade 12 minuta i temperatura od 60 °C

Application of high intensity ultrasound treatment on Enterobacteriae count in milk

Ultrasonication is a non-thermal method of food preservation that has the advantage of inactivating microbes in food without causing the common side-effects associated with conventional heat treatments, such as nutrient and flavour loss. In this work high intensity ultrasound was used to investigate inactivation Enterobacteriae count in raw milk. Raw milk with 4% of milk fat was treated with ultrasonic probe that was 12 mm in diameter and with 20 kHz frequency immerged in milk directly. For ultrasounds treatment, three parameters varied according to the statistical experimental design. Centre composite design was used to optimize and design experimental parameters: temperature (20, 40 and 60 °C), amplitude (120, 90 and 60 μm) and time (6, 9 and 12 minutes). All analyses were performed immediately after sonication and after 3 and 5 days of storage in refrigeration at 4 °C. The facts that substantially affect the inactivation of microorganisms using ultrasound are the amplitude of the ultrasonic waves, the exposure/contact time with the microorganisms, and the temperatureof treatment. The achieved results indicate significant inactivation of microorganisms under longer period of treatments with ultrasonic probe particularly in combination with higher temperature andamplitude. Output optimal value of Enterobacteriae count has been defined by Statgraphics where lowest Enterobacteriae count (1.06151 log CFU mL-1) was as follows for specific ultrasound parameters: amplitude of 120 μm, treatment time for 12 min and temperature of 60 °C

Effect of High Intensity Ultrasound Treatment on the Growth of Food Spoilage Bacteria

The aim of this study is to determine the effect of high intensity ultrasound (amplitude, temperature and treatment time) on the inactivation of food spoilage bacteria Escherichia coli 3014, Staphylococcus aureus 3048, Salmonella sp. 3064, Listeria monocytogenes ATCC 23074 and Bacillus cereus 30. The model suspensions of bacteria were treated with 12.7-mm ultrasonic probe operated at 600 W nominal power (ultrasonic treatment implemented at 20 kHz) and at amplitudes of 60, 90 and 120 µm. Also, treatment time of 3, 6 and 9 min and temperature of 20, 40 and 60 °C were used. The results were statistically processed with STATGRAPHICS Centurion computer program and response surface methodology. All three parameters studied seem to substantially affect the inactivation of bacteria in pure culture. The results also indicate increased inactivation of microorganisms under longer period of treatments, particularly in combination with higher temperature and/or amplitude. After ultrasonic treatment at 60 °C, 9 min and 120 μm, the viability of cells was not confirmed for Escherichia coli 3014, Staphylococcus aureus 3048, Salmonella sp. 3064 and Listeria monocytogenes ATCC 23074. Under the mentioned conditions the highest inactivation (3.48 log CFU/mL) of Bacillus cereus 30 was obtained

Utjecaj ultrazvuka visokog intenziteta na rast bakterija uzročnika kvarenja hrane

The aim of this study is to determine the effect of high intensity ultrasound (amplitude, temperature and treatment time) on the inactivation of food spoilage bacteria Escherichia coli 3014, Staphylococcus aureus 3048, Salmonella sp. 3064, Listeria monocytogenes ATCC 23074 and Bacillus cereus 30. The model suspensions of bacteria were treated with 12.7-mm ultrasonic probe operated at 600 W nominal power (ultrasonic treatment implemented at 20 kHz) and at amplitudes of 60, 90 and 120 µm. Also, treatment time of 3, 6 and 9 min and temperature of 20, 40 and 60 °C were used. The results were statistically processed with STATGRAPHICS Centurion computer program and response surface methodology. All three parameters studied seem to substantially affect the inactivation of bacteria in pure culture. The results also indicate increased inactivation of microorganisms under longer period of treatments, particularly in combination with higher temperature and/or amplitude. After ultrasonic treatment at 60 °C, 9 min and 120 μm, the viability of cells was not confirmed for Escherichia coli 3014, Staphylococcus aureus 3048, Salmonella sp. 3064 and Listeria monocytogenes ATCC 23074. Under the mentioned conditions the highest inactivation (3.48 log CFU/mL) of Bacillus cereus 30 was obtained.Svrha je ovoga rada bila utvrditi utjecaj ultrazvuka visokog intenziteta (velike amplitude, te pri višoj temperaturi i duljem vremenu obrade) na inaktivaciju bakterija što uzrokuju kvarenje hrane, i to: Escherichia coli 3014, Staphylococcus aureus 3048, Salmonella sp. 3064, Listeria monocytogenes ATCC 23074 i Bacillus cereus 30. Suspenzije bakterija tretirane su pomoću sonde promjera 12,7 mm, nominalne snage od 600 W (ultrazvučna je obrada provedena pri 20 kHz) sa tri amplitude (60, 90 i 120 µm), na temperaturi od 20, 40 i 60 °C, tijekom 3, 6 i 9 min. Rezultati su obrađeni programom STATGRAPHICS Centurion, pri čemu je korištena metoda odzivne površine, a utvrđeno je da sva tri ispitana parametra bitno utječu na inaktivaciju bakterija u čistoj kulturi. Rezultati pokazuju da je bolja inaktivacija mikroorganizama postignuta s duljim vremenom obrade ultrazvukom pri višim temperaturama i/ili većim amplitudama. Nakon ultrazvučne obrade na 60 °C i 120 µm tijekom 9 min potpuno su inaktivirane stanice bakterija Escherichia coli 3014, Staphylococcus aureus 3048, Salmonella spp. 3064 i Listeria monocytogenes ATCC 23074. Pri tim je uvjetima postignuta najveća inaktivacija bakterija Bacillus cereus 30 (3,48 log CFU/mL)

Utjecaj ultrazvuka visokog intenziteta na rast bakterija uzročnika kvarenja hrane

The aim of this study is to determine the effect of high intensity ultrasound (amplitude, temperature and treatment time) on the inactivation of food spoilage bacteria Escherichia coli 3014, Staphylococcus aureus 3048, Salmonella sp. 3064, Listeria monocytogenes ATCC 23074 and Bacillus cereus 30. The model suspensions of bacteria were treated with 12.7-mm ultrasonic probe operated at 600 W nominal power (ultrasonic treatment implemented at 20 kHz) and at amplitudes of 60, 90 and 120 µm. Also, treatment time of 3, 6 and 9 min and temperature of 20, 40 and 60 °C were used. The results were statistically processed with STATGRAPHICS Centurion computer program and response surface methodology. All three parameters studied seem to substantially affect the inactivation of bacteria in pure culture. The results also indicate increased inactivation of microorganisms under longer period of treatments, particularly in combination with higher temperature and/or amplitude. After ultrasonic treatment at 60 °C, 9 min and 120 μm, the viability of cells was not confirmed for Escherichia coli 3014, Staphylococcus aureus 3048, Salmonella sp. 3064 and Listeria monocytogenes ATCC 23074. Under the mentioned conditions the highest inactivation (3.48 log CFU/mL) of Bacillus cereus 30 was obtained.Svrha je ovoga rada bila utvrditi utjecaj ultrazvuka visokog intenziteta (velike amplitude, te pri višoj temperaturi i duljem vremenu obrade) na inaktivaciju bakterija što uzrokuju kvarenje hrane, i to: Escherichia coli 3014, Staphylococcus aureus 3048, Salmonella sp. 3064, Listeria monocytogenes ATCC 23074 i Bacillus cereus 30. Suspenzije bakterija tretirane su pomoću sonde promjera 12,7 mm, nominalne snage od 600 W (ultrazvučna je obrada provedena pri 20 kHz) sa tri amplitude (60, 90 i 120 µm), na temperaturi od 20, 40 i 60 °C, tijekom 3, 6 i 9 min. Rezultati su obrađeni programom STATGRAPHICS Centurion, pri čemu je korištena metoda odzivne površine, a utvrđeno je da sva tri ispitana parametra bitno utječu na inaktivaciju bakterija u čistoj kulturi. Rezultati pokazuju da je bolja inaktivacija mikroorganizama postignuta s duljim vremenom obrade ultrazvukom pri višim temperaturama i/ili većim amplitudama. Nakon ultrazvučne obrade na 60 °C i 120 µm tijekom 9 min potpuno su inaktivirane stanice bakterija Escherichia coli 3014, Staphylococcus aureus 3048, Salmonella spp. 3064 i Listeria monocytogenes ATCC 23074. Pri tim je uvjetima postignuta najveća inaktivacija bakterija Bacillus cereus 30 (3,48 log CFU/mL)