Importance of pH in Food Preservation

Play an AI-generated podcast conversation about this lesson

What effect does increasing the acid or alkalinity in a food have on the killing effect of heat?

Slows down the killing effect of heat

Increases the heat resistance of bacteria

Speeds up the killing effect of heat (correct)

Has no impact on the killing effect of heat

Which pH range categorization is correct for sauerkraut and pickles according to the text?

Medium acid to acid: pH 3.7 - 4.6

Low acid: pH > 4.6

Alkaline: pH > 7.0

High acid: pH < 3.7 (correct)

What is the term used to describe the ability of bacteria to produce stress proteins enabling them to grow in acid environments?

Acid adaptation

Acid tolerance

Acid habituation (correct)

Acidification

What does the text suggest about E.coli O157:H7 in relation to acidity?

It is highly resistant to acidic environments Signup and view all the answers

In terms of heat resistance, when are most bacteria maximally resistant?

At their optimum pH Signup and view all the answers

What is the equilibrium favored when the exterior pH is 4.0 and the pKa is 4.0?

RCOOH Signup and view all the answers

Intracellular pH of 7.0 results in the equilibrium favoring the formation of which compound?

RCOO- + H+ Signup and view all the answers

What is the role of ATPase in the process described?

Transporting H+ out at the expense of ATP Signup and view all the answers

A highly oxidized substrate, with a positive Eh value, is likely to support the growth of which type of microorganisms?

Strict aerobes Signup and view all the answers

What does the redox potential (ORP) value of a food indicate?

Its oxidizing or reducing power Signup and view all the answers

Which term refers to organisms that grow at 5-7 degrees Celsius regardless of their optimum growth temperature?

Psychrotrophs Signup and view all the answers

What happens to proteins above the maximum temperature for an organism?

Proteins are irreversibly damaged Signup and view all the answers

Which two pathogens mentioned are both mesophiles and psychrotrophs?

Yersinia enterocolitica and Campylobacter jejuni Signup and view all the answers

What effect does temperature have on chemical and enzymatic reactions in living organisms?

Reactions proceed faster at higher temperatures Signup and view all the answers

What do yeast and mold have in common regarding their growth temperature ranges?

Optimum temperature is closer to the maximum Signup and view all the answers

How does temperature below the minimum affect the growth of organisms?

It stops growth Signup and view all the answers

Which of the following is an example of an exogenous osmolyte?

Glycine betaine Signup and view all the answers

What happens to the cell membrane composition when bacteria take up exogenous osmolytes?

Increase trans form of unsaturated FA Signup and view all the answers

What is the pH range for acidophiles?

3.0 - 3.5 Signup and view all the answers

In what pH range do nearly all yeasts and molds have their optimum pH?

4.5 - 6.0 Signup and view all the answers

What happens to bacterial growth as pH increases from the optimum to the maximum?

Bacterial growth rate decreases Signup and view all the answers

What is the effect of an environment with a pH beyond the range for Vibrio cholerae?

Possible denaturation Signup and view all the answers

What is one of the molecular adaptations of psychrophiles to lower temperatures?

Production of cold shock proteins to overcome partial blocking of protein synthesis Signup and view all the answers

What is the role of unsaturated fatty acids in the cytoplasmic membranes of psychrophiles?

Promote a more liquid state of the membranes at low temperatures Signup and view all the answers

What type of microorganisms survive pasteurization but do not grow at pasteurization temperature?

Thermoduric microorganisms Signup and view all the answers

Which type of bacteria includes Bacillus and Clostridium as examples?

Spore formers Signup and view all the answers

What is a characteristic of the membrane fatty acids in psychrotropic bacteria?

Contain polyunsaturated fatty acids and long-chain hydrocarbons with multiple double bonds Signup and view all the answers

What are heat shock proteins in thermophiles known for?

Functioning optimally at high temperatures and being heat stable Signup and view all the answers