Exam 4 Flashcards
meat quality factors
tenderness
juiciness
flavor
color
odor
3 most important factors for palatability
Flavor (taste and aroma) * most important
tenderness
juiciness
meat palatability
Tenderness is essential for consumer acceptance
90% of US steaks are considered tender or very tender
recent studies suggest flavor is equally important
when tenderness is within an acceptable range, then flavor becomes MORE important to eating satisfaction
58% of consumers indicate flavor has more impact than tenderness
43% of consumers indicate tenderness has more impact than juiciness
Is tenderness influenced by marbling?
only 10% of the variation in tenderness is associated with the marbling “halo effect”
Meat tenderness
tenderness is essential for consumer acceptance
tenderness is one of the few variables that add value
what influences tenderness
contractile state of the muscle: shorter sarcomere length=tougher
enzymatic degradation: calpain protease system
connective tissue:
marbling: higher marbling=more tender
marbling and the halo effect
only 10% of the variation in tenderness is explained by marbling
marbling helps to lubricate the mouth and reduce the density
at least 2% marbling is needed for acceptable tenderness
flavor perception
flavor is based on perception not sensation: combo of taste and aroma
taste: perceived by taste buds primarily on the tongue
odor/aroma: detected by the olfactory system
greatest contributor to perceived flavor
low molecular weight volatile compounds bind to olfactory receptors and are responsible for perceived flavors
basic tastes in meat
sweet
sour
bitter
salty
umami
odor/aroma in meat
raw meat has little aroma and has a blood-like flavor
however raw meat is a reservoir of precursor compounds that develop into flavor and odor-causing compounds as a result of chemical reaction that occur during cooking
cooked meat flavors
stem from:
the Maillard reaction, which combines amines and sugars to produce “meaty” flavor
thermal oxidation of lipids during cooking which produces volatiles/aromatics accounting for species flavor difference
volatiles produced during cooking that contributes to meat flavor
compounds formed in mailard reaction: aldehydes pyrazines
compounds formed during lipid thermal oxidation: alcohols aldehydes, hydrocarbons, ketones
amount composition of IM fat affects flavor profile of meat
IM lipids and associated volatiles produced during cooking are primary contributors to the flavor and aroma of meat
animal production practices that affect meat flavor do so primarily via effects on amount of composition of IM fat
effect of marbling degree on the palatability of a positive sensory experience
the higher the marbling the more likely a positive sensory experience
grain finishing for 100 days
produces grain-fed beef flavor
increase beef flavor, decrease fishy, decrease milky-oily
pre-harvest stress can influence flavor
important to avoid stress associated with handling and transport prior to harvest
compared to normal beef, dark cutting beef has a less desirable flavor with a higher incidence of off-flavors often characterized as:
bloody/serum like, sour, bitter, soapy
PSE pork tends to have an acidic flavor
Forage-finished beef affects on beef fat composition
higher levels of omega-3 polyunsaturated fatty acids, C 18:1 trans fatty acids, and stearic acid
all of which are negatively correlated with flavor desirability
flavor often characterized as grassy, gamey, livery, milky/oily, or fishy
Grain-finished beef affects on beef fat composition
higher levels of oleic acid, linoleic acid, and other monounsaturated fatty acids
all of which are positively correlated with flavor desirability
desired before fat flavor often characterized as “buttery”
Other factors affecting flavor
species: red meat and poultry
breed: bos indicus vs bos taurus
sex: androstenone, skatole
diet: grain fed vs grass fed
age: young lamb vs mutton
packaging: MAP, over-wrap, vacuum
fat
muscle
aging
enhancement
cooking method
Meat Quality
tenderness
juiciness
flavor
odor
color
multiple processes deteriorate these properties: bacterial, chemical, enzymatic, and physical activity
maintenance of these desirable properties= shelf life
meat discoloration
meat discolors much before it spoils
the best indicator of spoilage is smell
importance of meat color
consumer base purchasing decisions off od meat color: more important than any other factor
color is an indicator of freshness or wholesomeness: if not bright cherry red may be perceived as spoiled or unwholesome
discoloration influences meat purchases: at 20% discoloration discrimination by consumers, at 40% discoloration rejection by consumers
discoloration influences meat purchase: 15% of retail beef is discounted due to discoloration, and annual revenue loss >3.7 billion
importance of meat color continued
color plays a large role in determining retail case life:
consumers consider bright red/pink to be desireable, deviations may create unacceptability
consumers determine quality through appearance
discoloration is considered unwholesome
many biochemical, physical, and microbiological factors affect color: understanding causes for discoloration helps with management of color
utilization of tools to maximize retail case life
how is meat color measured
CIE L, a, and b* values
hue: trueness of red; arctangent (b/a)
chroma: intensity or degree of color saturation; (a^2 + b^2)^1/2
subjective color measurements: how the individual eye perceives color, trained or consumer panels
L*
lightness (z axis: 0-100)
greater L* = lighter sample
lower L*= darker sample
a*
redness (x-axis; +60 to - 60)
greater a* means more red
b*
yellowness (Y axis; +60 to -60)
greater b* means more yellow the sample
myoglobin
sarcoplasmic protein
primary protein responsible for meat color
contain 8 alpha helies and a prosthetic group
water soluble and contains protein and non protein portions: non protein heme ring, protein globin
heme ring of myoglobin
centrally located Fe that can for 6 bonds:
4 bonds with pyrrole nitrogen
5th bond with proximal histidine (amino acid portion of globin)
6th binding site can reversibly bind ligands and other compounds
nature of the group attached to the 6th binding site & chemical state of iron determines meat color
chemical state of iron
color influenced by compounds that interact with Fe in the Heme Ring: ability to bind with myoglobin depends on valance (charge) of Fe
when reduced (ferrous, 2+) myoglobin readily binds oxygen or H2O
the valance state of Fe depends on availability of electrons: ETC, enzymes use residual O2 long after harvest
ferrous vs ferric
ferrous= reduced
ferric= oxidized
chemical forms of myoglobin
primary forms of myoglobin:
deoxymyoglobin (DMb)
oxymyoglobin (OMb)
metmyoglobin (MMb)
carboxymyoglobin (COMb)
deoxymyoglobin
occurs when H2O or no ligand is available for binding to 6th site
heme iron is ferrous (Fe2+)
publish-red or purplish-pink color
requires very low or no oxygen: commonly seen in vacuum packages
oxymyoglobin
occcurs when O2 is bound to the 6th binding site: myoblgoin has very high affinity for O2
bloom= oxygenation
heme iron is ferrous (Fe2+): same valance state as BMb (no change in electrons
bright cherry red color
requires continuous exposure to O2: OMb penetration increases with exposure, not a stable formation, eventually promotes oxidation
metmyoglobin
oxidation of ferrous (Fe2+) Mb to ferric (Fe3+): loss of an electron
resulting in brown or tan color: undesirable
why does MMb form
insufficient oxygen to form OMb
depletion of electrons
contamination (aerobic bacteria)
MMb formation is gradual: MMb located between internal DMb and superficial Omb, gradually thickens and moves to surface
carboxymyoglobin uses
COMb is visually indistinguishable from Pmb
CO inhibits pathogenic bacteria growth
CO inhibits lipid oxidation promoting desirable flavor
CO promotes color, but doesn’t inhibit natural spoilage processes
odor of fresh meat equally important as color
carboxymyoglobin
formed when DMb is exposed to CO: not a naturally occurring reaction, Myoglobin has a higher affinity for CO than O2 (CO poisoning)
Heme iron is ferrous (Fe2+), forming a stable red color (stability depends on CO availability)
CO is approved for use in meat packaging systems to 0.4%
Metmyoglobin reduction
this process doesn’t last forever
reduction of MMb brown (Fe3+) to DMB red (Fe2+): changes meat color from becoming brown
a muscles ability to transition is termed metmyoglobin reducing ability: varies by muscle, postmortem age, pH, Temp, etc
electrons are the currency of meat color
deoxymyoglin Fe2+ (purple) is oxidized to oxymyoglobin
oxymyoglonim Fe2+ (red) is reduced to metmyoglobin
Metmyoglobin Fe3+ (brown) can be reduced back to deoxymyoglobin as long as enzymes are available to do so
other forms of myoglobin
Nitric Oxide Myoglobin (NOMb): cure pink, stable with the addition of heat
Cyanmetmyoglobin (CNMb): stable red
Suflmyoglobin (SHMb): green, product of microbial contamination
Choleglobin (H2O2): green, product of microbial contamination
Nitric Oxide Myoglobin
involved in processed meat production: nitrites are added for preservation, flavor and color development (curing)
Myoglobin (purple) + NO = nitric oxide myoglobin (red) + heat = nitrosylhnechromagen (cured pink)
Nitric Oxide Myoglobin (natural)
the use of celery powder and sea salt to add nitrates to cure meat
pre harvest effects on meat color: diet
antioxidants prevent oxidation retarding the development of MMb:
vitamin E supplementation to live cattle improves OMb stability
pre-harvest effects on meat color: housing and management
loose housed cattle have darker muscles than stalled cattle
increased # of slow twitch fibers, vascularization and oxidative metabolism
pre-harvest effects on meat color: stress
PSE and DFD
pre-harvest effects on meat color: chill rate
temperature at which muscle enters rigor affects color: deviations in fat thickness, thickness of muscle
non-uniformity in muscle color due to pH/temperature decline
why is packaging important
food packaging serves to protect products against deteriorating effects, contain the product, communicate to the consumer as a marketing tool, and provide consumers with ease of use and convenience
many quality factors can be influenced by packaging: if meat doesn’t look good a consumer will not purchase it
packaging properties that influence shelf life
package type: aerobic and anaerobic
headspace and atmosphere
packaging equipment
temperature
utilization of correct package extends shelf life
increasing shelf life by 1-2 days would save US meat industry up to $1 billion annually
History
70+ years ago: butcher shops and full-service meat markets
1950s to present: convenience, increased federal oversight, and competition with other proteins lead to commercialized packaging
Histotial changes in meat packaging
meat cut and harvest by the consumer: animals harvested as needed
meat cut by butcher: wrapped in wax paper
1950s: increased overwrap packaging
1950s-1990s: advances in packaging technology, barrier packaging (restrict atmosphere influence), are permeability, moisture permeability
1990s-current: implementation of new tech, case ready, modified atmosphere, skin pack, Darfresh, Nitrite embedded, etc
change from passive to active packaging
active packaging is the incorporation of specific compounds into packaging systems to maintain or extend product quality and shelf life while intelligent or smart packaging provides for sensing of the food properties or package environment to inform the processor, retailer, or the consumer of the status of the environment or food
has evolved to provide and enhance many functions for the product itself:
use of antioxidants, antimicrobials, and novel package types. smart packaging tells you if product is good or bad
wholesale meat packaging
relies on vacuum packaging technology: primals/subprimals are centrally packaged before distribution
critical to efficiency of modern meat packaging industries: advanced equipment multi-chambered & heat sealing
can package at minimum 50 pieces per minute
vacuum packaging
utilized for “boxed” meat
oxygen impermeable bags: 3-ply laminates
ethyl vinyl acetate (tough outer layer), saran (middle oxygen layer), irradiate ethyl vinyl acetate (heat sealing)
extend shelf life:
reduce aerobic spoilage bacteria, no oxygen=less oxidation, requires strict temperature control, control of anaerobic microorganisms
disadvantages: purge, consumer acceptability (no oxygen= deoxymyoglobin= purple color)
retail meat packaging
more variety than wholesale packaging
more focus on shelf-life maintenance and appearance
-traditional overwrap, chub, vacuum on a board
traditional overwrap packaging
traditional: meat cut and packaged on site
uses polymer based tray and barrier films
moisture impermeable: keeps moisture out and keeps moisture in
oxygen permeable: allows for “bloomed” color (oxymyoglobin), prolonged exposure leads to oxidation
light permeable: rapid photo-oxidation, leads to faded color issues
disadvantage: leads to spoilage the fastest
case ready packaging
what is case ready: fabrication nd packaging of “consumer-sized” retail items in a centralized non-retail location for shipping to retail location
why case ready: an average of 10% greater profits versus store-cut meat. more control and less cross-contact contamination, less labor for retail stores
500 mil in 1997
2.8 billion in 2005
83% of all protein sales in 2018
modified atmosphere packaging
MAP: defined as removal or replacement of the atmosphere surrounding the product before sealing in vapor-barrier materials
multiple formats: tray sealed, master bag and overwrap tray, vacuum skin packaging, laminate, pouches
MAP is the method used for carboxymyoglobin color preservation in meat
Tray sealed high oxygen:
80% O2 and 20% CO2 most common,
promotes the development of oxymyoglobin,
decreased shelf life via aerobic bacterial growth and oxidation
Tray sealed low oxygen
various amounts of CO2 and N2
promotes development of deoxymyoglobin
more than 30% CO2 results in absorption of CO2 by meat
tray sealed Carbon Monoxide
no oxygen
0.4% approved for use in meat
promotes development of carboxymyoglobin
changes in case ready
ten years ago tray sealing was sweeping the industry
currently declining acceptance of tray sealed meats: bulky increasing shipping costs, consumer perception
how can industry utilize case ready without giving appearance of case ready
master-bag or master package
master packaging
placement of “traditional” package types into MAP packaging: gives the appearance that meat was packaged at retail store
internal package: overwrap, one exception is PVC is micro-perforated
Multiple atmospheres can be used in master packaging: most common is carbon monoxide
vacuum skin packagin
relatively new type of case-ready
advantages: enhanced shelf life, reduced oxidation & microbial growth, attractive appearance, small footprint
disadvantages: formation of deoxymyoglobin, can be overcome with newer technologies (nitrate films), expensive
rollstock, laminates, & pouches
relatively new type of case-ready
advantages: convenience, attractive appearance, small footprint
disadvantages: rollstock machines often have problems
chub packaging
increasing in prevalnce: >15% of ground beef sold in 2016
common for ground meats
advantages: economical, branding and identity, easy to handle/store, longer shelf life
disadvantages: formation of deoxymyoglobin, temperature control is essential, consumer cannot see meat
ground beef shelf life days
least long shelf life: carcass trim ground in store, case ready overwrap
longest shelf life: bulk chub reground in store, vacuum packaged primal
ground beef shelf life days
least long shelf life: carcass trim ground in store, case ready overwrap
longest shelf life: bulk chub reground in store, vacuum packaged primal
poultry packaging
largely different from red meats
unlike red meat, color isn’t primary in poultry packaging
packages are selected to enhance safety and convenience:
whole bird bags, SSD/SES stretch and shrink films, pillow packs, tray-sealed
packaging trends
convenience is driving the market: consumers want meat that is easy to store/prepare/cook. smaller and single serve portions, cook-in-bag, recipes on the bag
sustainability and green packaging: reduced environmental impact, recyclable & biodegradable, made from reused material (plant pulp, recycled paper waste)
Whats in a label
seven components to each label
1) accurate product name
2) list of ingredients
3) name and place of business packer, manufacturer, or person whom product is prepared
4) net weight
5) official federal or state inspection stamp
6) official plant number
7) handling instructions, if the product is perishable
pathogen
bacteria (microorganisms) that cause infections (disease).
they can be spread through food consumption and cause foodborne illness
CDC estimates that 1/6 Americans get sicked 128,000 get hospitalized and 3,000 die of foodborne illness.
4 important bacteria classifications
Gram stain and bacterial cell wall
temperature requirement
oxygen requirement
pH of Growth
Gram Stain
knowing this will help us understand which antibiotics will work on the infection
temperature requirements bacteria
psychrophiles: grow at 0 degrees C or below max 20 degrees C, optimal 15
facultative psychrophiles: can grow at 0 degrees C, optimal 20-30 degrees C
mesophiles: grow between 25-40 degrees C, optimal 37 degrees C, *human pathogens
thermophiles: grow above 40 degrees C
hyperthermophiles: optimum temperature above 80 degrees C
Oxygen requirements
*important for packaging
obligate aerobes: require oxygen
microaerophiles: require oxygen at low concentrations
obligate anaerobes: require no oxygen
facultative anaerobes: can use oxygen prefer no oxygen
aerotolerant anaerobes: no need for oxygen but tolerant
pH requirements
acidophiles:
neutrophiles
alkaliphiles
Stages of bacterial growth
1) LAG bacteria are metabolically active but not growing (where we want to keep bacteria)
2) EXPONENTIAL time of bacteria growth (doubling)
3) STATIONARY growth and death rate are equal (nutrients depleted)
4) DEATH exponential decrease in number of living cells (nutrients depleted, waste accumulated)
Intrinsic factors that affect bacterial growth
physical and chemical properties of the meeat
nutrients
pH
water activity
extrinsic factors
associated with the environment in wich the meat is stored
temperature
gaseous environment
storage time
Pathogens of major concern
Shiga toxin-producing Escherichia coli (STEC) O157:H7
Salmonella enterica
campylobacter jejuni
listeria monocytogenes
Shiga Toxin produding E. coli
Enterobacteriaceae
gram negative, rod shaped, non-spore forming, motile
mesophile (35 degrees C), facultative anaerobe, neutrophile
infection dose 10 cells,
beef specifically ground beef, the 7 STEC are listed as adulterants in fresh/raw non-intact beef
Salmonella
enterobacteriaceae
gram negative, rod shaped, flagellated motile
mesophile (37 degrees C), facultative anaerobes, neutrophile
infection dose 1000 cells non-typhoidal to 100,000 enteric fever cells
poultry products, pork and beef, specifically ground beef (lymph nodes)
Campylobacter
campylobacteriacae
gram negative, sprial shaped, motile
thermophilic (37-42 degrees C), microaerophilic (O2 5-10%), neutrophils
infection dose <500 cells
poultry and pork products (cases increase as poultry consumption increase)
C. jejuni os responsible for more than 80% of enteric campylobacter infections and E. coli 10%
Lister Monocytogenes
listeriaceae
gram positive, small rod shaped, flagellated motile
psychrotrophic (-1.5 to 45 degrees C, optimal 30-37), facultative anaerobes, neutrophils
infection dose <10,000,000 cells
ready to eat meats (deli meat)
adulterant in RTE meat
Reducing Bacteria
MULTIPLE HURDLES
pre-harvest and post-harvest interventions
post harvest: physical decontamination, chemical interventions, refrigeration
further processing: drying, cooking, curing and smoking
how do we evaluate these interventions
in lab evaluation: in-vitro broth study, in-vivo with meat
(use pathogenic bacteria)
in plant evaluation: validation study (use of surrogates)
surrogates: non-pathogenic microorganisms that behaves similar to the pathogen of interest (FSIS approved)
Pseudomonas spp>
non-pathogenic meat spoilage bacteria
obligate aerobes, psychotropic,
responsible for putrefaction smell, spoilage levels produce hydrogen sulfide bonds to myoglobin resulting in green color
Lactic Acid Producing Bacteria
non-pathogenic meat spoilage bacteria
aerotolerant anaerobes (can survive vacuum packaging)
lactobacillus is the largest genus
acid fermentation (sour off-flavor), gas production, and slime secretion
