Food Science 1

Purpose of vegetable fermentations?

-Preserve vegetables and fruits (initially the main objective) -Develop characteristic sensory properties: flavor, aroma and textures -Changes in nutritional properties of product --Decrease phytate content and increasing bio-availability of iron --Reduction of nitrate content through nitrate and nitrite reductase activity

What is a retort, when is it used, and how does pH influence this decision?

-Processed in a can or pouch -Retort processing utilizes pressure to generate temperatures higher than boiling (>212°F, >100°C). -Typically, processing temperatures will be around 250°F (121°C). -Process is designed to destroy spores of Clostridium botulinum.

What is aseptic processing?

-Product is heated to high temperatures, ie 250°F (121°C) to destroy spores of Clostridium botulinum -The product is cooled, and then filled into containers that have also been sterilized.

Why are preservatives added to foods

-Prolong shelf-life -Prevent chemical spoilage -Slow or eliminate microbiological spoilage a) Bacterial b) Yeast c) Molds -Reduce or eliminate dangerous pathogenic bacteria

What is a psychrotrophic bacteria?

-Psychrotrophic organisms have the ability to grow at 4°C, but it might not be their optimal growth temperature. -These can be yeast, molds or some bacteria, that can spoil food products.

How does Kimchi fermentation differ from sauerkraut?

-Similar amount of salt, but shorter incubation time -Less acidic final product

How are sugar and salt preservatives?

-Small amounts of sugar or salt are isotonic, meaning water can easily move in and out of bacterial cell. -Larger amounts of sugar or salt will lower aw , and acts as a hypertonic solution. The bacterial cell loses water. This process is known as "PLASMOSIS"

Definition of food fermentation

A food product or ingredient that is biochemically unique and produced via microbial growth.

What is whey?

A greenish yellow mixture of water, protein, and lactose that remains after curds are produced in cheese.

What is pumace?

A mixture of seeds and skins

What is food spoilage

A physical change

What are lees?

A sediment of: Yeast Pulp Salts

Why is sorbic acid added to food products?

Active against Yeasts and Molds

Which federal agency is involved in regulating processed foods?

FDA

Which federal agency is involved in regulating produce?

FDA

What does heating do to microorganisms?

Food is preserved using heat to destroy either: -Pathogenic bacteria -Spoilage microorganisms

What does FSMA stand for?

Food safety modernization act

What is the difference between food spoilage and food safety?

Food spoilage -A physical change in the food product that is no longer appetizing. Food safety -Food can appear appetizing, however it may contain human pathogens that have the potential to cause illness.

The Orleans process of vinegar fermentation is a batch process performed in __________

A barrel

Bacteria Cell shapes Cell structures

Cell shapes -Bacterial shapes can vary --Rod or bacillus --Cocci --Spiral Cell structures -single celled organisms

Molds Cell structure growth characteristics

Cell structure -Multicellular growth characteristics -Produce many spores which can be transported via dust

Yeasts Cell structure growth characteristics

Cell structure -Single cell growth characteristics -Divide by budding

Louis Pasteur

Disproved Spontaneous Generation and devised pasteurization of wine

Which organism (general name) is used in the first part of acetic acid fermentation? What is the substrate and end product?

Part 1: Yeast (anaerobic) 1 glucose 2 CO2 + 2 Ethanol (alcohol)

Which organism (general name) is used for the second part of the fermentation? What is the substrate and end product?

Part 2: Acetic acid bacteria Ethanol + Oxygen Acetic acid + Water

Heterofermentative lactic acid bacteria?

Produces lactic acid and other end products (carbon dioxide gas and ethanol).

What is the metabolic end product of growth of a homofermentative lactic acid bacteria?

Produces only lactic acid as an end product of growth.

How does refrigeration preserve foods?

Prolongs lag phase

Why are do manufactures use sulfur dioxide resistant wine yeasts? What does the sulfur dioxide do?

SO2 is added in to: -Inhibit undesirable yeasts and other organisms -Help pigment release by breaking open cells on grape skins -Prevent browning -Help preserve flavor

What organism is used for wine making?

Saccharomyces cerevisiae var ellipoids

What are the differences between set, stirred and Greek style yogurts?

Set yogurts -Fermentation in the package. Firm gel Stirred yogurts -Fermentation in vessels with agitation. Soft gel Greek style yogurt -Can be stirred or set. Has a straining or filtration step to reduce water and increase milk solids, either before or after the fermentation.

Norovirus

Virus Infection

Why can't you just add acid to milk to get yogurt?

Well, you can but it won't taste very good...

What type of gel is cheese?

concentrated milk

What are the good characteristics of a good yeast?

resistant to Sulfur dioxide

Water activity can be reduced by

(1) Adding solutes (increase N1 ) Addition of Salt or Sugar (2) Reduce the amount of water (decrease N2 ) Drying or Dehydration process

Bacterial Growth phases

(1)Lag Phase: Period of Adjustment, (2)Exponential Phase: Period of Rapid Growth (1 → 2, 2 → 4, 4 →8 etc.) (3)Stationary Phase: Lack of nutrients signal period of little-to-no growth, but cells are still metabolically active (4)Death Phase or Sporulation Death phase - Long after stationary phase, cells die due to lack of nutrients and metabolic waste. Sporulation - cells that sporulate will do so in stationary phase under the right conditions

bacterial growth Temperature Psychrophile

(cold loving) Growth below 7°C

bacterial growth Temperature mesophile

(middle loving) Growth around body temp

bacterial growth "Danger Zone"

-Between 40°F (4°C) and 140 °F (55°C) is the "Danger Zone" No more than 2h in the Danger Zone to keep foods safe.

What is added to vegetable fermentations in order to inhibit the growth of undesirable organisms?

-Carbohydrates -Sodium Chloride

What is the purpose of pasteurization? Are all organisms destroyed?

-Designed to destroy spoilage yeasts and molds, but will also kill pathogenic vegetative bacteria. -Sporeforming bacteria may still be present, but the low pH prevents growth. Therefore, these products are shelf stable.

Robert Koch

-First to conceptualize and prove germ theory and disease -Koch's Postulates

How is C. botulinum growth controlled in canned foods?

-Heating product to destroy C. botulinum spores. Or -Lowering the pH of the product below pH 4.6, which inhibits germination of the spores. -Lowering aw to below 0.85 to inhibit germination of spores

Which populations are more susceptible for FBI?

-Infants and young children -The elderly -Immunocompromised - such as cancer patients, transplant recipients, diabetics, persons who are HIV+ or have AIDS. -In some illnesses, pregnant women

Min pH of microorganisms growth

-Most bacteria cannot grow at a pH less than 4.0 - 6.0. -Some bacteria can grow down to pH 3.0-4.0, especially those that produce acid as an end product of growth (we'll talk more about this in the fermentation lecture). -Yeasts and Molds grow down to a minimum pH of between 2.0 - 5.0

pH

-Neutral pH is 7 -acidotic pH Less than (<) pH 7 -basic pH Greater than (>) pH 7

What is UHT processing?

-Very high temperature (250- 300°F for 1-2 sec) processing. -Destroys all vegetative and most spore forming organisms. -Used to create shelf stable processed products or long shelf life refrigerated product

Why are nitrites added to cured meats?

-prevent the growth of the spores of Clostridium botulinum, which produced a deadly bacterial toxin . -Contribute to pink color -Contribute to flavor

theoretical no water aw =

0

pH Scale

0-14

Scale of water activity: pure water aw =

1

What are the atmospheric conditions of fermentation?

15-20°C is optimal. Can occur more slowly down to 10°C.

Campylobacter jejuni

Bacteria Infection

E. coli O157:H7

Bacteria Infection

Listeria monocytogenes

Bacteria Infection

Salmonella sp

Bacteria Infection

Staphylococcus aureus

Bacteria Intoxication

Clostridium Botulinum

Bacteria Spore Former Intoxication

Min aw for microbial growth

Bacteria at aw > 0.85 Yeast at aw > 0.70 Molds at aw > 0.60

Bacterial grow in a process known as______

Binary Fission

What is a natural fermentation?

In natural fermentations, the fermentation conditions are adjusted to favor the growth of Lactic Acid Bacteria naturally on the plant material.

What are the two mechanisms of foodborne illness?

Infection Intoxication

What disaccharide is in milk?

Lactose

Anton Van Leeuwenhoek

Made microscopes and first to observe microorganisms

What does drying do to microorganisms?

Microorganisms do not grow due to lack of water

How does freezing preserve foods?

Microorganisms will not grow in a frozen product, but freezing does not destroy all microorganisms.

What are the four main ingredients in cheese?

Milk Rennet Salt Starter cultures (lactic acid bacteria)

Propionic acid is found naturally in which food?

Naturally present in Swiss Cheese

How is C. botulinum controlled in processed meats?

Nitrite is added to control C. botulinum

What is the most common foodborne virus in the US? What are the main symptom?

Norovirus • symptoms nausea vomiting diarrhea abdominal cramps

Which federal agency is involved in regulating meat?

United States Department of Agriculture

What are the differences between white, red and rose wines?

White wine -Grapes are pressed immediately and the pomace (skin and seeds) is separated. -Yeast is added and fermentation takes place Red wine -The juice and pomace are inoculated with yeast and are sent together to tanks for a 4 to 14 day fermentation -The pomace is pressed out. During the fermentation, red wine gets its color for the pigment in the skins - as well as strong flavor and astringency from tannins and other substances in the skin and seeds. Rosé wine -The juice and yeast are allowed to remain in contact with the pomace for only a 24 h period. -After pressing and removal of the pomace, fermentation continues.

What type of gel is yogurt?

acid set gel

What is microbial fermentation?

an anaerobic metabolic processes that converts sugar (substrate) into acid, gases and/or alcohol (end product).

bacterial growth Temperature Thermophile

heat loving Growth above 45°C

Commercial vinegar formation utilized a fermenter with the acetic acid bacteria growing on __________________.

loosely packed wood chips

The pH used to define a High Acid Food for heat processing

pH 4.6

Bacterial Generation time

the amount of time it takes for 1 bacterium to divide into 2 bacteria.