Lab 3 | Quizlet

What are the two main causes of food spoilage?

1. Non-microbial changes → O₂ + light

- Oxidative rancidity

- Physical injury

- Chemical changes

2. Microbial growth → bacteria + yeasts + moulds

What does full inspection procedure consist of?

- Label verification

- Organoleptic inspection of samples (sensory assessment)

- Microbiological examination of samples

What is meat preparation?

- Meat undergoing preparation without altering internal muscle fibre structure

- Characteristics of meat still present

- E.g. minced meat with > 1% salt

What is a meat product?

- Product formed from processing meat or meat preparation

- Muscle fibre structure no longer visible when cut

- E.g. sausages

What external defects occur in cured meats?

- Surface mould growth

- Yeast/bacteria growth → biological frost

- Salt efflorescence → crystalline frost

- Non-microbial discoloration

Describe surface mould

- Spots on sausage casing

- Uncontrolled mould growth

- Colours → grey, green, yellow, blue-green, black

- Spots may be separate or confluent

- Earliest change at binding site

- Strong characteristic odour

- Microscope → filamentous structure

Factors favouring mould growth

- Poor air quality in storage rooms

- Poor ventilation

- Too much raw material

- Small production area

- Breaks in refrigeration chain → surface moisture

How is pigmented mould removed?

By washing sausage casing

What is the problem with removing mould by washing?

- Improves appearance only

- Toxic + allergenic metabolites remain in meat

What is biological frost?

Growth of yeasts + bacteria on sausage surface

Microorganisms causing biological frost

Yeasts:

- Debaryomyces

- Pichia

Bacteria → G(+) cocci

- Enterococcus

- Streptococcus

Appearance of biological frost

- Grey-green or whitish spots

- Sharply separated

- Dry matte surface

- Granular structure

- Earliest change at binding site

Factors favourable to biological frost

- Humidity: > 90%

- Temp: > 12°C

- Distance between sausages: < 4–5 cm

What is salt efflorescence (crystalline frost)?

Salt crystals forming on sausage casing

Causes of salt efflorescence

- Insufficient soaking of natural casings before stuffing

- Diffusion of salts from over-salted filling

Appearance of salt efflorescence

- Glossy spots on surface

- Usually on natural casings

- Can resemble biological frost

Describe non-microbial discoloration

- Grey-green discoloration

- Red, yellow or blue spots may appear

Causes of non-microbial discoloration

- Casing too tight

- Incorrect smoking

- Incorrect storage

- Light exposure

What internal defects occur in cured meats?

- Discoloration under casing layer

- Mucus fermentation

- Meat putrefaction

What does discoloration under casing layer look like?

- Usually in fermented sausages

- Cross section shows

→ 1-3 mm thick layer

→ Grey, green or brown colour

→ Clearly separated from core

Factors causing discoloration under casing layer

- Water poorly removed from soaked casings

- Rapid cooling of smoked meat

- Temp too low

- High humidity

- High microbial contamination

What causes mucus fermentation?

Growth of Bacillus

Factors contributing to mucus fermentation

- Too much sugar in meat batter

- Poor hygiene → cross contamination

- Contaminated raw material

What is observed when sausage is broken in mucus fermentation?

- Thread of mucus

- Jelly-like structure

What causes meat putrefaction?

Growth of putrefactive bacteria

Factors contributing to meat putrefaction

- Long storage

- High storage temp

- Poor hygiene

- Faults in technological process

How should organoleptic inspection of sausages be performed?

- Cut sausage at both ends + middle

- Smell product during cutting

- Inspect area under casing first

Why is area under casing inspected first?

Microbial activity begins there

What physical hazards may be found during organoleptic inspection?

- Bone fragments

- Packaging material (foil)

What defect may indicate risk of rancidity?

Presence of oxygen bubbles

What are the aims of microbiological exam?

- Protect human health from pathogens + toxins

- Prevent microorganisms causing product deterioration

What is purpose of microbiological testing?

Determine degree of bacterial contamination

How can microbiological testing be performed?

- Qualitative testing

- Quantitative testing

What is qualitative microbiological testing?

Detect presence of microorganisms

Example of qualitative testing

- Contact analysis

- Impression plate

What does contact analysis verify?

Effectiveness of cleaning + disinfection

What is quantitative microbiological testing?

Determines number of microorganisms

Units used in quantitative testing

- CFU per gram

- CFU per cm²

Methods used in quantitative testing

- Destructive method

- Swab method

What is destructive method?

Standardized piece of meat cut from product surface

What is total plate count?

Measures total contaminating microflora

What does total plate count determine?

Number of viable microorganisms

What agar is used for total plate count?

Nutrient agar

What is selective plate count?

Determines specific microorganisms

What media are used in selective plate count?

- Selective media culture

- Chemical additives suppress unwanted bacteria

Describe total plate count method

- 10g meat + 90 mL sterile water

- Homogenise in stomacher

- Serial dilution (1:10 → 1:100 → 1:1000)

- Transfer 1 mL to Petri dish

- Spread with sterile stick

- Incubate

Incubation conditions for total plate count

- 12–24 hrs at 35–37°C

or

- 24–48 hrs at 30°C

What colony numbers are countable in plate counts?

25-250 CFU

What does CFU mean?

Colony forming unit

What is pure culture?

Culture containing one species/strain

What is a colony?

Population of cells from one cell or spore

When are Durham tubes used?

Detect gas production by microorganisms

How are Durham tubes placed?

Inserted upside down in broth

What broth is used to detect coliforms in the lab?

Brilliant green bile broth (2%)

What indicates presence of coliforms?

- Gas production

- Colour change

- Turbidity

What determines characteristics of sausages?

- Type of meat

- Product formulation

What formulation factors influence sausage characteristics?

- Salt content

- Sugar content

- Nitrate/nitrite

- Spices + additives

What determines characteristics of fermented sausages?

- Starter culture vs natural flora

- Organisms used

- Fermentation temp

- Cooking

- Smoking

- Mold ripening

- Drying level

Bacteria used in starter cultures

- Lactobacillus plantarum

- Pediococcus

→ produce lactic acid

What is role of Micrococcus in fermented sausage?

Converts nitrite → nitrate

What chambers are used in sausage fermentation?

- Fermentation chamber

- Drying chamber

- Drying/storage chamber

Temperatures used in fermentation chamber

- No starter → 16–20°C

- Fast culture → 24–40°C

Temperatures in drying chamber

12-16°C

Temperatures in drying/storage chamber

10-12°C

Difference between dry fermented + semi-dry sausages

Dry fermented:

- Moisture 25–45%

- E.g. salami, pepperoni

Semi-dry:

- Moisture 40–50%

- E.g. cervelat

What is microbiological criteria?

Tool used to assess food safety + quality

Aim of microbiological criteria

Define max acceptable microbial contamination level

→ ensure safety + suitability

What does microbiological criteria in the Regulation 2073/2005 contain?

- Sampling plan

- Laboratory method

- Stage in food chain

- Corrective action

What is food safety criteria (FSC)?

Assess safety of final product

What is FSC applicable to?

Products placed on market during shelf life

What happens if FSC is not met?

Product withdrawn or recalled

What is process hygiene criteria (PHC)?

Indicates correct functioning of production process

What happens if PHC levels are not met?

Improve production hygiene + raw material selection

What does m mean?

Lower acceptable limit

What does M mean?

Upper acceptable limit