The document discusses water activity (aw), which is an important factor that determines the development of microorganisms. aw represents the available water content in a substrate that microorganisms can use for their metabolic activity. It is defined as the ratio between the equilibrium vapor pressure of water in a food and the vapor pressure of saturated water vapor at the same temperature. aw values range from 0-1 and influence the growth and toxin production of various microorganisms. Foods are categorized based on their aw values as high, intermediate, or low moisture foods.
Gradivo sedmog razreda osnovne škole. Postavljene animacije. Snimljeno predavanje. Rastvor, homogena smeša, zasićen, nezasićen i prezasićen, zavisnost rastvorljivosti supstance od promene temperature, određivanje rastvarača, agregatna stanja, rastvorljivost kiseonika u vodi - vodeni ekosistem
Redox potential (Eh) is a physicochemical concept that reflects the ratio of oxidized and reduced forms of metabolites in a substrate. It acts selectively on the development of microorganisms in foods. Eh is expressed as a Eh-value, which is actually a measure of the oxidizing or reducing power of a chemical system. Reductions and oxidations are inseparable processes based on the transfer of electrons from one material to another. Materials that easily release electrons are good reducing agents, and those that easily accept electrons are good oxidizing agents. The redox potential of a substrate depends on pH, chemical composition, presence and mutual relationship of reductive (SH groups of proteins, hydrogen sulfide, ascorbic acid
The document discusses pH and its impact on microorganisms. It defines pH as the negative logarithm of hydrogen ion concentration and describes the pH scale. It provides examples of the optimal and tolerated pH ranges for various bacteria, and discusses how pH affects the growth and development of different groups of microorganisms in foods. It also gives approximate pH values of various foods and explains how other environmental factors can interact with pH to impact microorganism growth.
Gradivo sedmog razreda osnovne škole. Postavljene animacije. Snimljeno predavanje. Rastvor, homogena smeša, zasićen, nezasićen i prezasićen, zavisnost rastvorljivosti supstance od promene temperature, određivanje rastvarača, agregatna stanja, rastvorljivost kiseonika u vodi - vodeni ekosistem
Redox potential (Eh) is a physicochemical concept that reflects the ratio of oxidized and reduced forms of metabolites in a substrate. It acts selectively on the development of microorganisms in foods. Eh is expressed as a Eh-value, which is actually a measure of the oxidizing or reducing power of a chemical system. Reductions and oxidations are inseparable processes based on the transfer of electrons from one material to another. Materials that easily release electrons are good reducing agents, and those that easily accept electrons are good oxidizing agents. The redox potential of a substrate depends on pH, chemical composition, presence and mutual relationship of reductive (SH groups of proteins, hydrogen sulfide, ascorbic acid
The document discusses pH and its impact on microorganisms. It defines pH as the negative logarithm of hydrogen ion concentration and describes the pH scale. It provides examples of the optimal and tolerated pH ranges for various bacteria, and discusses how pH affects the growth and development of different groups of microorganisms in foods. It also gives approximate pH values of various foods and explains how other environmental factors can interact with pH to impact microorganism growth.
15.uticaj procesnih parametara na rast i razmnožavanjeMaja Andjelkovic
Temperature is a key process factor that affects microbial growth and reproduction in foods. Microorganisms have three cardinal temperatures - minimum, optimum, and maximum temperatures - for growth. The optimum temperature for the growth of most pathogenic and spoilage microorganisms in foods is around 30°C.
The document discusses various extrinsic environmental factors that affect the growth of microorganisms, with a focus on temperature. It describes how microorganisms can be classified based on their optimal temperature ranges for growth, including psychrophiles, mesophiles, and thermophiles. The effects of temperature on microbial physiology and metabolism are explored, as well as its implications for food storage and safety.
The document discusses pH and its impact on microorganisms. It defines pH as the negative logarithm of hydrogen ion concentration and describes the pH scale. It provides examples of the optimal and tolerated pH ranges for various bacteria, and discusses how pH affects the growth and development of different groups of microorganisms in foods. It also gives approximate pH values of various foods, meats, seafoods, and dairy products.
This document discusses nutrient utilization and microbial growth. It summarizes that microorganisms require nutrient-rich mediums containing amino acids and vitamins for growth. Milk contains low levels of free amino acids and peptides, so microbes have developed complex proteolytic systems to break down milk proteins into usable peptides and amino acids. These systems include extracellular proteinases and intracellular peptidases that hydrolyze proteins and peptides. The proteolytic system allows microbes to obtain essential amino acids needed for growth.
This document discusses the nutrients and conditions needed for the growth of microorganisms in foods. It notes that microbes break down proteins, fats, and carbohydrates in foods and can produce beneficial or harmful compounds. Under favorable conditions like sufficient nutrients and proper storage, microbe populations can increase exponentially to 107 cells/g within 8 hours. Controlling intrinsic factors such as pH, water activity, and antimicrobial components is important for microbiological control of foods.
This document discusses factors that influence the growth and development of microorganisms in food, including intrinsic, extrinsic, and implicit factors. Implicit factors relate to the microorganisms themselves, such as initial number, growth phases/reproduction rate, and interactions. A higher initial number of microorganisms and species adapted to the substrate and environment conditions allows for faster adaptation. Faster reproduction rates, represented by shorter generation times, also allow for more rapid growth under favorable conditions. Unfavorable substrate conditions prolong the generation time for all microorganisms.
2. AKTIVNOST VODE (aw) JE ZNAČAJAN
FAKTOR OD KOGA ZAVISI RAZVOJ
MIKROORGANIZAMA , I PREDSTAVLJA
SADRŽAJ UPOTREBLJIVE VODE U
SUPSTRATU, TJ TO JE ONAJ DEO VODE
KOJI JE DOSTUPAN
MIKROORGANIZMIMA ZA NJIHOVU
METABOLIČKU AKTIVNOST
3.
4. ZA RAZVOJ MIKROORGANIZAMA
U NAMIRNICAMA NIJE BITAN
UKUPAN SADRŽAJ VODE, NEGO
DEO TE VODE KOJU ONI MOGU
KORISTITI TJ. SADRŽAJ
SLOBODNE VODE
5. AKTIVNOST VODE JE FIZIČKA
VELIČINA KOJU JE U
MIKROBIOLOGIJU NAMIRNICA UVEO
SCOTT (1953)
A DEFINIŠE SE KAO ODNOS IZMEĐU
RAVNOTEŽNOG PRITISKA VODENE
PARE U NAMIRNICI (p) I PRITISKA
ZASIĆENE PARE (ps) PRI ISTOJ
TEMPERATURI:
aW=p/ps odnosno
aw= relativna vlažnost vazduha (%) /100
6. AKTIVNOST VODE SE
IZRAČUNAVA BROJEVIMA OD 0-1
AKTIVNOST VODE SUVE
MATERIJE JE NULA, A
DESTILOVANE VODE JEDAN
7. AKTIVNOST VODE ZAVISI OD
SADRŽAJA VODE U NAMIRNICI
OD VRSTE I KOLIČINE MATERIJALA
RASTVORLJIVIH U VODI ( SOLI,
ŠEĆERI, NEPROTEINSKA AZOTNA
JEDINJENJA
I OD NAČINA VEZIVANJA VODE
(ZA PROTEINE, UGLJENE HIDRATE I
DISPERGOVANE VODE U EMULZIJAMA)
8. MINIMALNE aW-VREDNOSTI ZA
RAZMNOŽAVANJE VAŽNIH MIKROORGANIZAMA
aW MIKROORGANIZMI
0,97 Pseudomonas spp., C. botulinum tip E
0,96 Shigella spp., Klebsiella spp.
0,95 Salmonella spp., C. botulinum tipA, C. perfringens, B. cereus,
E. coli, Proteus spp.
0,94 C. botulinum tip B, Aerobacter spp., Vibrio parachemolyticus
0,93 Lactobacillus spp., Lactococcus spp.
0,92 Rhodotorulla spp.
0,90 Micrococcus spp., Pediococcus spp., B. subtilis,
Saccharomyces
10. MINIMALNE aW –VREDNOSTI PRI KOJIMA
MIKROORGANIZMI AKTIVNO RASTU
GRUPA MIKROORGANIZAMA MIN. aW –VREDNOSTI
VEĆINA G- BAKTERIJA 0,97
VEĆINA G+BAKTERIJA 0,90
VEĆINA KVASACA 0,88
VEĆINA PLESNI 0,80
HALOFILNE BAKTERIJE 0,75
KSEROFILNE PLESNI I 0,62-0,60
OSMOFILNI KVASCI
11. GRAFIČKI PRIKAZ
PODRUČJA
aW-VREDNOSTI
U KOJIM SE
RAZMNOŽAVAJU
POJEDINE GRUPE
MIKROORGANIZA
MA
12. VEĆINA MIKROORGANIZAMA SE RAZMNOŽAVA
PRI RELATIVNO VISOKIM aw-VREDNOSTIMA
KSEROFILI PODNOSE NISKE aw-VREDNOSTIMA,
JER SE RAZMNOŽAVAJU U SREDINI SA VRLO
MALO VODE
OSMOFILI PODNOSE VISOKE KONCENTRACIJE
SOLI PA S TIM I NIŽU aw-VREDNOSTIMA
HALOFILI KOJI SE MOGU RAZMNOŽAVATI SAMO
U VISOKIM KONCENTRACIJAMA SOLI (>15%)
PODNOSE NISKE aw-VREDNOSTIMA
13. SMANJENA aw-VREDNOST UTIČE NA:
RAST MIKROORGANIZAMA U LAG
FAZI
EKSPONENCIJALNOJ FAZI I U
STACIONARNOJ FAZI
14. MIKROORGANIZMI POSEBNO OSETLJIVI NA
SMANJENJE aw-VREDNOST
GRAM NEGATIVNE BAKTERIJE
(Pseudomonadaceae, Enterobacteriaceae,
prestaju sa rastom ako je aw-VREDNOST
niža od 0,96)
PATOGENE I TOKSOGENE VRSTE
(Salmonella spp., B. cereus., C. botulinum tip A, E.
coli prestaju sa rastom ako je aw-VREDNOST
niža od 0,95)
15.
16. NA OSNOVU aW NAMIRNICE SE SVRATAVAJU
1. NAMIRNICE VISOKE VLAŽNOSTI
(HIGH MOISTURE FOODS HMF) SA
aw=0,90-1,0
2. NAMIRNICE SREDNJE VLAŽNOSTI
(INTERMEDIATE MOISTURE FOODS IMF) SA
aw=0,60-0,90
3. NAMIRNICE NISKE VLAŽNOSTI
(LOW MOISTURE FOODS LMF) SA
aw=<0,60
17. NAMIRNICE VISOKE VLAŽNOSTI
(HIGH MOISTURE FOODS HMF) SA
aw=0,90-1,0
OPTIMALNO ZA RAST MNOGIH
MIKROORGANIZAAM
BARENE I KUVANE KOBASICE
DIMLJENI PROIZVODI
KONZERVE
FERMENTISANE POLUSUVE KOBASICE I
FERMENTISANE KOBASICE ZA MAZANJE
MLEKO I FERMENTISANI PROIZVODI OD
MLEKA
18. NAMIRNICE SREDNJE VLAŽNOSTI
(INTERMEDIATE MOISTURE FOODS IMF) SA
aw=0,60-0,90
U OVIM PODRUČJIM BAKTERIJE SLABO
RASTU I NAMIRNICE SE MOGU ČUVATI
BEZ HLAĐENJA
- SUVOMESNATI PROIZVODI
- FERMENTISANE SUVE KOBASICE
- EKSTRA TVRDI I TVRDI SIREVI
NA POVRŠINI SUVIH PROIZVODA SE
POJAVLJUJU KSEROFILNE PLESNI
– Aspergillus spp. I Penicillium spp.
19. NAMIRNICE NISKE VLAŽNOSTI
(LOW MOISTURE FOODS LMF) SA
aw=<0,60
LIOFILIZOVANI PROIZVODI
KVAR NAMIRNICA JE HEMIJSKE PRIRODE
I NASTAJE PRETEŽNO USLED
OKSIDACIJE MASTI
20. ODNOS SADRŽAJA VODE I
aW-VREDNOSTI U NAMIRNICAMA
SORPCISKA IZOTRMA
PODRUČJE A-VODA JE
NEISKORISTIVA ZA
HEMIJSKE REAKCIJE
PODRUČJE B-PRELAZNA
ZONA U KOJOJ SE
NAGOMILAVA SLOBODNA
VODA U KAPILARIMA
PODRUČJE C- SLOBODNU
VODU KOJA JE SPOSOBNA
REAGOVATI SA DRUGIM
MOLEKULIMA
21. MINIMALNA aW-VREDNOST PRI
KOJOJ SE RAZMNOŽAVAJU
MIKROORGANIZMI ZAVISI, TAKOĐE,
OD INHIBITORNIH EFEKATA
DRUGIH ČINILACA, KAO ŠTO SU
- TEMPERATURA
- pH
- Eh
23. STVARANJE TOKSINA U ZAVISNOSTI OD
aW I T(OC)
AFLATOKSIN B1
1. A. flavus
2. A. parasiticus
OKRATOKSIN A
1. A. ochraceus
2. P. verrucosum var.
cyclopium
3. P. verrucosum var.
verrucosum