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
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
Takmičenje na portalu www.nasaskola.net
"biramo najbolju lekciju"
februar 2012. godine,
Alkoholi,
Biologija,
Nataša Stojanović, III-4,
Jasmina Miljković,
Prva niška gimnazija "Stevan Sremac"
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
Takmičenje na portalu www.nasaskola.net
"biramo najbolju lekciju"
februar 2012. godine,
Alkoholi,
Biologija,
Nataša Stojanović, III-4,
Jasmina Miljković,
Prva niška gimnazija "Stevan Sremac"
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.
B.sc. (micro) i em unit 2 microbial growth & nutrition aRai University
This document discusses microbial nutrition, growth, and environmental factors that affect bacteria. It covers temperature, pH, oxygen requirements, and osmotic pressure. Temperature classes include mesophiles, psychrophiles, and thermophiles. Most bacteria grow best between pH 6-8, but some are acidophiles or alkaliphiles. Organisms also differ in their oxygen requirements, ranging from obligate aerobes to obligate anaerobes. High solute concentrations impact osmophiles and halophiles. Growth is measured by changes in population over time using various methods like plate counts or turbidity.
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 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.
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. REDOKS POTENCIJAL JE FIZIČKO
HEMIJSKI POJAM KOJI
ODRAŽAVA ODNOS
OKSIDOVANOH I REDUKOVANIH
OBLIKA METABOLITA U
SUPSTRATU
3. REDOKS POTENCIJAL DELUJE
SELEKTIVNO NA RAZVOJ
MIKROORGANIZAMA U NAMIRNICAMA
IZRAŽAVA SE KAO Eh-VREDNOST ŠTO
JE ZAPRAVO MERA ZA OKSIDUJUĆU
ODNOSNO REDUKUJUĆU MOĆ NEKOG
HEMIJSKOG SISTEMA
4. REDUKCIJE I OKSIDACIJE SU
NERAZDVOJNI PROCESI KOJI SE
ZASNIVAJU NA PRELASKU ELEKTRONA
OD JEDNE MATERIJE NA DRUGU
MATERIJE KOJE LAKO OTPUŠTAJU
ELEKTRONE SU DOBRI REDUKUJUĆI
AGENSI A ONE KOJE LAKO PRIMAJU
ELEKTRONE SU DOBRI OKSIDUJUĆI
AGENSI
5. OKSIDO –REDUKUJUĆI (REDOKS)
POTENCIJAL JE SPOSOBNOST
SUPSTRATA DA PRIMA
ELEKTRONE (REDUKCIJA) ILI DA
GUBI ELEKTRONE (OKSIDACIJA)
6. PRELASKOM ELEKTRONA SA
JEDNOG JEDINJENJA NA DRUGO
JAVLJA SE RAZLIKA U
ELEKTRIČNOM POTENCIJALU
IZMEĐU TIH JEDINJENJA KOJA
MOŽE DA SE MERI U mV
7. AKO SUPSTRAT MOŽE OPSTATI U
OKSIDOVANOM OBLIKU X I U
REDUKOVANOM OBLIKU X- TAKAV SE
PAR NAZIVA REDOKS PAROM
REDOKS POTENCIJAL TOGA PARA
MOŽE SE ODREDITI MERENJEM
ELEKTROMOTORNE SILE
ODGOVARAJUĆE ELEKTRODE U
ODNOSU PREMA STANDARDNOJ
(REFERENTNOJ) VODONIKOVOJ
ELEKTRODI
10. NEGATIVNI REDOKS POTENCIJAL
ZNAČI DA SUPSTRAT IMA MANJI
AFINITET ZA ELEKTRONE OD
VODONIKOVOG ATOMA
POZITIVAN REDOKS POTENCIJAL
ZNAČI DA SUPSTRAT IMA VEĆI
AFINITET ZA ELEKTRONE OD
VODONIKA
11. JAKI REDUCENT (npr.NADH) IMA
NEGATIVAN REDOKS
POTENCIJAL, A JAKI OKSIDANS
(POPUT O2) IMA POZITIVAN
REDOKS POTENCIJAL
12. SUPSTRAT U KOJEM DOMINIRAJU
OKSIDACIONI PROCESI IMA
POZITIVNE
A SUPSTRAT U KOME
PREOVLAĐUJU REDUKCIONI
PROCESI IMA NEGATIVNE Eh-
VREDNOSTI
14. NEKI VAŽNI REDOKS PAROVI I
NJIHOVI STANDARDNI REDOKS
POTENCIJALI
PAR EO(mV)
1/2O2/H2O +820
Fe+3/Fe+2 +760
CITOHROM C OKS./RED. +250
DEHIDROASKORBINSKA +80
KIS./ASKORB. KIS
METILENSKO PLAVO OKS/RED +11
PIRUVAT/LAKTAT -190
NAD+/NADH -320
15. REDOKS POTENCIJAL MESA ZAVISI OD
pH, HEMIJSKOG SASTAVA, PRISUSTVA
I MEĐUSOBNOG ODNOSA
REDUKTIVNIH (SH –GRUPE PROTEINA,
SUMPOR VODONIK, ASKORBINSKA
KISELINA I ŠEĆERI) I OKSIDATIVNIH
MATERIJA (NITRATI, NITRITI),
PARCIJALNOG PRITISKA KISEONIKA I
AKTIVNOSTI MIKROORGANIZAMA
16. KISEONIK JE NAJUTICAJNIJI REDOKS
PAR U NANIRNICAMA
POVEĆAN ULAZ VAZDUHA U
NAMIRNICU KAO POSLEDICA REZANJA,
MLEVENJA, SECKANJA DOVEŠĆE DO
POVIŠENJA Eh
SIROVO MESO (POSLE RIGORA)
-200E(mV)
SIROVO ISECKANO MESO +225 E(mV)
17. REDOKS POTENCIJAL BARENIH
KOBASICA JE OD -20 DO -100mV
KONZERVI OKO -100 mV
SVEŽE SALAMURE OD +450 DO +
600 mV
18.
19. DODAVANJE NAMIRNICAMA
NITRATA I NITRITA Eh SE
POVEĆAVA
Eh U NAMIRNICAMA SE SMANJUJE
AKO IM SE DODAJE
ASKORBINSKA KISELINA I DRUGI
ANTIOKSIDANSI
20. REDOKS POTENCIJAL MESA SE
SMANJUJE PRI ZAGREVANJU, JER SE
OSLOBAĐA SUMPOR-VODONIK IZ
PROTEINA
REDOKS POTENCIJAL ĆE SE SMANJITI
AKO SE U SUPSTRATU RAZMNOŽAVAJU
MIKROORGANIZMI KOJI TROŠE
KISEONIK
21.
22. U UNUTRAŠNJOSTI ZRELOG MESA
REDOKS POTENCIJAL JE NIZAK-
UTICAJ REDUKUJUĆIH GRUPA
KOJE NASTAJU U PROCESIMA
ZRENJA (SH GRUPE) – POGODUJE
RASTU ANAEROBNIH BAKTERIJA
23. NA POVRŠINI NAMIRNICA ILI
NEPOSREDNO ISPOD POVRŠINE
VLADAJU AEROBNI USLOVI U KOJIMA
SE RAZMNOŽAVAJU AEROBNI
MIKROORGANIZMI.
DELOVANJE AEROBNIH
MIKROORGANIZAMA NA PROTEINE
DOVODI DO OSLOBAĐANJA SH GRUPA,
KOJE SLABE LOKALNU TENZIJU
KISEONIKA
24. MNOGE VRSTE IZ RADA BACILLUS
NISU INHIBIRANE EVAKUACIJOM
VAZDUHA, UKOLIKO PRITISAK
REZIDUALNOG VAZDUHA NE
PADNE ISPOD 10mm Hg, ŠTO
ODGOVARA PO2 OD 2mm Hg