BIOTECH LEC 2 - Fermentation of fruits and vegetables

• eliminate anti-nutritional ingredients

• rise the finished product’s shelf life

• add value to improve prospects for jobs and income generation

• eliminate anti-nutritional ingredients

• rise the finished product’s shelf life

• add value to improve prospects for jobs and income generation

Why are agricultural crops processed?

Fermentation

One of the most ancient and relevant techniques for food production

fermented fruits

What are the first fermented foods

• it is efficient

• low energy preservation process

• appropriate technique for use in developing countries and remote areas

• it supplies protein, minerals, and other nutrients

Why is fermentation important?

“Gundruk”

is a fermented and dried vegetable product from Nepali

gari and fufu

Fermented cassava products in Africa

Fermentation

Slow decomposition process of organic substances induced by microorganisms, or by complex nitrogenous substances of plant or animal origin

anaerobic or partially anaerobic oxidation of carbohydrates by microorganisms or enzymes

What brings about the biochemical change in fermentation?

Putrefaction

Degradation of protein materials

Fruits

The edible product of a plant or a tree, consisting of the seed and its envelope

fruits

called ‘high acid’ foods since nearly all are acidic

yeasts and mold

spoilage organisms likely to be found on fruit products

1. tropical fruits

2. decreases

The acidity level of (1) such as banana, mango, and papaya (2) as the fruit ripens

vegetables

A plant cultivated for food, especially an edible herb or root used for human consumption

vegetables (often requires some form of processing to increase their edibility)

called ‘low acid’ foods due to their lower levels of acidity

by making them more acidic, either through pickling, salting, or drying

How can low acid food be safely preserved?

Low acid foods

prone to deterioration by microorganisms and provide an ideal substrate for food poisoning organisms when in a moist environment

Agro-processing

describes the transformation of agricultural produce into a different physical or chemical state

“agro”

Encompasses a wide range of food and non-food agricultural products

“food processing”

applies only to products which are suitable for human consumption

Agro-processing

applies to any of the numerous activities that take place in the chain of events between harvest/slaughter of the raw material and production of the final product

Salometer

Salt present in a brine is expressed as degrees (% saturation of NaCl by weight)

26.359g per 100mL at 15.5 C (10 degree Salometer contains 2.64% salt by weight)

A saturated solution of pure sodium chloride (100 degrees Salometer) contains:

Biotechnology

application of scientific and engineering principles to the processing of materials, for the provision of goods and services, through the use of biological systems and agents

• complex carbohydrates

• ex. starch and cellulose

• One that is composed of long branched chains of single sugar units

• Give examples

• Reducing sugar (all simple sugars)

• glucose, fructose, or galactose

sugar which has reactive aldehyde or ketone groups

Microorganism/Microbe

generic terms for the group of living organisms which are microscopic in size

Enzyme

Biological catalyst which is used to facilitate and speed up reactions

above 42 C

temperature at which mammalian proteins (and therefore enzymes) are denatured

Facultative anaerobe

microbes that can adapt to exist with or without oxygen

Microaerophilic

Microbes that requires small amounts of oxygen for survival

free and bound

Water exists in two states within a cell

Water activity

measure of the amount of free water available for potential reaction - microbial or enzymic

0 to 1.0 where 1.0 is the activity of pure water

water activity is measured on a scale of

pH

measure of the hydrogen ion concentration

scale of 1 to 14, where 1 represents high concentration of hydrogen ions (acidic) and 14 represents low concentration (alkaline)

How is pH measured?

neutral (pH 7.0)

optimum pH for most microorganisms

• high acid foods - pH 4.6 or lower

• low acid foods - pH is above 4.6

pH of high and low acid foods

• Improves food security

  • food preservation

  • salvaging waste foods

  • removal of anti-nutritional factors

• Increases income and employment

• Improves nutrition (vitamins and digestibility)

• Medicinal benefits

  • protects from disease

• Improve cultural and social well-being

  • improve flavor and appearance of food

  • Creation of meat-like flavor

benefits of fermenting fruits and vegetables

Koumiss

fermented milk product in Russia used to treat tuberculosis

Pulque

fermented fruit sap in Mexico containing medicinal properties

lactic acid fermentation

Fermented fruit and vegetables products arise from

• Bacteria

  • Lactobacillus spp., Acetobacter spp.,

• Yeasts

  • Saccharomyces spp.,

• Molds

Organisms responsible for food fermentation

enzymatic activity

changes that occur during fermentation of foods are the result of

catalysts

initiates and control reactions rather than being used in a reaction

Desirable fermentation

only the desired bacteria, yeasts, or molds start to multiply and grow on the substrate

• Moisture

• Oxygen concentration

• Temperature

• Nutrients

• pH

• Inhibitors

Manipulation of growth and activity

Yeasts

unicellular fungus which reproduces asexually by budding or division

• some are chromogenic and produce green, yellow, and black pigments

• others can synthesize essential B group vitamins

What are yeasts?

chromogenic

producing pigments

• Abundance of oxygen for growth

• Basic substrate such as sugar

Conditions necessary for fermentation

alcohol and carbon dioxide

yeasts can ferment sugars to ____ in the absence of air

ethyl alcohol and carbon dioxide

yeasts produce _____ from simple sugars

0 to 50 C; optimum 20 to 30 C

temperature range necessary for fermentation

pH 4.0 to 4.5

pH range necessary for fermentation

0.85

Water activity necessary for fermentation

• clarification and pre-treatment of juice

• chemical composition of juice

• temperature of the fermentation

• influences of other microbes

Factors affecting wine fermentation

• Red grape wine

• White grape wine

• Banana beer

• Cashew wine

• Tepache

• Palm wine

• Basi (sugarcane wine)

types of fermented fruit juices

Bacteria

Large group of unicellular or multicellular organisms lacking chlorophyll

spherical, rodlike, spiral, or filamentous

Shapes of bacteria

Lactic acid bacteria

gram (+) bacteria, non-respiring, non-spore forming, cocci or rod shaped

Lactic acid

Major end product of the fermentation of carbohydrates

• Lactobacillus

• Leuconostoc

• Pediococcus

• Streptococcus

Types of lactic acid bacteria

• sour dough bread

• sorghum beer

• all fermented milk

• cassava

• most pickled vegetables

lactic acid bacteria are responsible for the fermentation of:

Acetic acid bacteria (Acetobacter spp.)

produces a vinegary off-taste in the wine

Acetobacter

convert alcohol to acetic acid in the presence of excess oxygen