Food between farm gate and consumption Flashcards

Question

What are the three main mechanisms by which heat is transferred?

Answer 1

Conduction, convection and radiation

Answer 2

Conduction – Heat energy is transferred from one molecule to an adjacent molecule (through containers) without a gross change in the relative positions of the molecules – Heating of solid foods

Answer 3

Convection ## Footnote – Transfer of heat by groups of molecules that move as a result of differences in density or as a result of agitation – Heating of fluid foods

Answer 4

Radiation ## Footnote – Heat transfer by electromagnetic waves emitted by hot objects (infrared range, wavelength 750 nm to 1 mm) – Infrared, microwave, dielectric heating

Answer 5

What is the primary objective to cooking? In crease palatability. Baking, roasting, dry heat Preservative changes? Some destruction of spoilage and pathogenic microrganisms. Inactivation of deteriroative enzymes Other desierable changes? Inactivation of some anti-nutritional factors (Lectins in pulses). Improved digestability of some food constitients Undesirable changes? Loss of nutrients. Decline in sensory quality (with too much heating).

Answer 6

* Lysine bioavailability reduced by nonenzymatic browning * Heat sensitive vitamins: decrease in bioavailability (not concentration) – vitamin A, vitamin D * Loss of water soluble vitamins: decrease in concentration (and bioavailability) – thiamine, niacin, folate

Answer 7

Main objective- inactivate deteriorative enzymes. Kill spoilage bacteria. Atmospheric or pressurized steam. Less severe than canning Normally done prior to freezing or canning of veg and drying of fruit.

Answer 8

Loss of nutrients during blanching is mainly due to leaching, thermal destruction, oxidation * As ascorbic acid is water soluble it is often leached from cells. It is also thermally labile and subject to enzymatic breakdown. * Therefore, loss of ascorbic acid is used as an indicator of the severity of the blanching process

Answer 9

Blanching with steam and air cooling (instead of rinsing)

Answer 10

A heat treatment which kills part of the microbial population present in a food – Minimum changes in sensory or nutritive value • Pasteurization of milk – Primary objective is to kill pathogenic microorganisms; shelf life is extended due to reduction in spoilage organisms and deteriorative enzymes – Target pathogens: was Mycobacterium tuberculosis (TB), now Coxiella burnetti (Q fever)

Answer 11

LTH (low temp, hold) = 63°C for 30 min --\> LTH is more detrimental to nutritional and sensory properties. HTST (high temp, short time or flash) = 72°C for 15 sec

Answer 12

Batch process – Milk is heated in holding tank for a certain time – Used only in small-scale operation • Continuous process – Milk flow through a heat exchanger while the desired time/temperature treatment is obtained – Equipment: Plate heat exchanger (PHE) • High production rate • No overheating of milk

Answer 13

Beer, juice, eggs

Answer 14

Sterilization or “commercial sterilization” is the process used in canning, retorting and UHT (ultra high temp) processing of food – Done at a much higher temperature than pasteurization • It is also called Appertization, after the French scientist Nicolas Appert, who in 1810 won a prize from Napoleon for discovering way to preserve food by enclosing in hermetically sealed containers

Answer 15

Low-acid foods (pH \> 4.5) – Acid foods (pH 3.7 to 4.5) – High-acid foods (pH \< 3.7)

Answer 16

ASEPTIC packaging!!!!

Answer 17

Heat transfer during sterilization of cans in retort occurs via: – Conduction through can wall and solid foods – Convection through liquid foods • Need to make sure the cold point (x) has reached desired temperature and time

Answer 18

Thermal conductivity is a measure of how fast a solid material can be heated

Answer 19

The amount of heat energy required to raise the temperature of a mass unit of a substance by 1 degree celcuis

Answer 20

– Nature and heat resistance of the microbial population – Initial microbial load (How many microbes are present?) – Nature of the food (pH, chemical composition) – Heat transfer characteristics of the container – Heat transfer characteristics of the food – Conditions of storage (liquid? How will it be stored?) – Characteristics of the canning equipment • “still” retort vs. one with agitation

Answer 21

The survivor curve is the logarithmic releationship betweeen the number of survivors of a given microorganism and the time oh heat at that given temp This is because the number of microorganisms in a food is reduced when it is subjected to heat treatment for a certain time.

Answer 22

True -The slope of this curve (survival rate per unit time) is related to sensitivity/resistance of the the microorganism to heat.

Answer 23

The heat resistance of microorganisms is expressed in terms of the time needed to kill 90% at a given temperature -D-value

Answer 24

D value (decimal reduction time) -The number of minutes required at a particular temperature and in a particular medium to destory 90% of the microorganisms (10% survival) in a population --\> or to decrease the population by one log cycle

Answer 25

If we know the d-value at a particular temp for our target organism and the number of organisms present, we can calculate how long it will take to destory the entire population Often assume that there are 10^12 of an initial bacterial population, since we don't usually know how many are initially present. --\> So we heat for 12 x D, which is known as a 12 D process. To kill all the bacteria present!

Answer 26

Before processing: Type of microorganism, growth temp, medium and phase During: Type of food, pH, water activity, salt concentration. Concentration of microorganism (how much is present before processing?), rate of heating After processing: Recovery medium (can they recover after processing?), temp. Presence of oxygen. Background microflora chance of growth in the medium?)

Answer 27

Acid and salt accelerate the destruction of microorganisms Protein denaturation (during processing) Generation of cooked flavour due to reaction of sulfur (S) from amino acid cysteine Maillard Browning reaction between reducing sugars and proteins-loss of nutirents (and important AA's) Loss of heat sensative vitamins

Answer 28

Also D-value D-valuse for nutirent: decimal reduction time for nutrient degradation at retort temp Bacterial cells and spores are more heat sensative than nutrients Imporved nutrient retention can be achieved with a high temp short time (HTST) process. -accelerated lethal rate at high temp. -Shorter process time prevents nutrient degradation form proceeding very far.

Answer 29

Freezing Refers to storage of food at temperatures between -18 and -30 degrees celcius. Freezing reoves free water required for microbial growth.

Answer 30

-Removal of sensible heat until freezing temperature – Removal of latent heat of fusion leading to ice formation – Further removal of sensible heat towards storage temperature

Answer 31

Fast freeze= numerous small ice crystals Slow freeze= fewer, but larger ice crystals

Answer 32

Ice crystals first form between the cells, as they have lower concentration of solutes there.

Answer 33

1. Large ice crystals damage cellular structure of frozen vegetables and lead to loss of structural integrity (food becomes very soft) 2. Formation of large crystals in inter-cellular region of vegetables pulls water out of the cell (due to osmotic equilibrium) - results in cellular dehydration. --\> Ice crystals outside of the cell will force free water out of the cell to maintain equilibrium. 3. On thawing the cells unable to maintain rigidity due to dehydration and disruption of cell wall by ice crystals – leading to soft, flaccid texture and loss of water

Answer 34

--\> Many small ice crystals, and all freeze together * Rapid freezing results in higher ice crystal nucleation rate which lead to formation of numerous small ice crystals both outside and inside the cells of frozen vegetables * Cells maintain their rigidity and minimizes drip loss of water during thawing of frozen vegetables * However, disruptive effect of size of ice crystals is minimum in fish or meat (muscle food) due to the elasticity of the cellular structure in muscles – The mechanism of loss of quality due to slow freezing of muscle foods is different than fruits and vegetables

Answer 35

Loss of quality of muscle food is due to denaturation of muscle proteins – During freezing unfrozen region become concentrated with enzymes and and acids which denatures muscle proteins and affect its functionality – Increased salt concentration in the unfrozen water also produces protein denaturation * This denaturation of protein occurs during formation of ice crystals in slow freezing in the temperature range 0º to -5ºC * This can be avoided by rapidly freezing the product (meat) such that the ice crystal formation zone (0º to -5ºC) passes as quickly as possible Faster freezing is better for muscle foods and veg.

Answer 36

1. temperature differential between the food and cooling medium 2. heat transfer rate of cooling medium (air or refrigerant) 3. surface area of food 4. product thickness 5. Agitation of liquid product

Answer 37

In frozen food products enzymes remain active, so unwanted enzyme activity in the frozen state may lead to loss of colour, flavour, lipid oxidation and also loss of nutrients * To avoid this, vegetables must be blanched prior to freezing * For fruits, if blanching is not option, ascorbic acid can be added to stop enzyme activity in frozen state

Answer 38

– The process of freezing does not significantly kill microorganisms already present in food – Blanching prior to freezing kills some microorganisms – During freezer storage, the growth of microorganisms significantly reduced and a gradual decrease in their number can be observed – However, often there can be sufficient survivors that can multiply and give problem during the thawing process – Temperature fluctuation during frozen storage can also lead to similar problem

Answer 39

Decrease in humidity in freezer may lead to sublimatation of ice on food surface= freezer burn -Loss of food weight, dry out surface (discolouration, protein dentaturation), loss of texture, rancidity development.

Answer 40

Relative humidity inside the freezer should be kept above 90%. REduce air movement across the food prodcuts. Glazing of food prior to freezing. Glazing is the formation of a layer of water or aq sol'n on food surcae that turns into an ice coat during freezing. Glaze layer protects food from loss of moisture and prevents freezer burn. Use of food packaging, prevents freezer burn and oxidation.

Answer 41

Air-blast freezer and tunnel freezer. Air blown over, air frozen.

Answer 42

Belt freezer (spiral belt freezer). Rotating belt, mostly for frozen meat.

Answer 43

Fluidized-bed freezer. Cold air spray from bottom, fluid bed on top to freeze product.

Answer 44

Scraped-surface freezer Widely used for ice cream manufacturing. Food froen on surface and scraped off by blade as freezes.

Answer 45

Cryogenic freezing Cooling with liquid nitrogen (-196 degrees C) or dry ice (solid CO, -79degrees C) or liquid ammonia (-33 degrees C) RAPID freezing.

Answer 46

Individual quick freezing Foods frozen individually for ease of consumer use. Rapid freezing with small ice crystal formation. Dehydration may be a concern, water sprayed before freezing (glazing) to control drying. Amount of water gain must be regulated.

Answer 47

What are three things to consider for freezing vegatables? - Blanch prior to freezing (to inactivate damaging enzymes) - Small loss of nutrients while freezing - On thawing, there may be more leaching compared to fresh veg.

Answer 48

During frozen storage, some loss of vit C will occur. On thawing, substancial vitamin loss happens in fruit syrup/juices, unless you consume it!

Answer 49

Most fruits and vegetables are high in water, low in proteins and fats • They are good sources of carbohydrates – Digestible: sugars and starches – Indigestible: cellulose, hemicellulose, lignin and pectic materials * Cell wall of young plants are relatively thin and composed largely of cellulose held together by pectin * With aging the wall thickens and higher amount of tough fibrous hemicellulose and lignins are formed

Answer 50

Fruits are generally good source of: – Specific vitamins and minerals – Natural sugars – Organic acids – Flavor compounds – Bioactive phytochemicals

Answer 51

Climacteric fruits- Harvested immature so that they may ripen by the time of consumption. Can ripen during shipping. (apples, bananas, melon, tomatoes) Non-climacteric fruits- Are harvested in fully ripened state and msut be consumed quickly. Don't ripen during storage, can't ripen off the tree. (Grapes, strawberries, citrus fruits)

Answer 52

Growth phase encompasses cell division and enlargement causing an increase in size * Maturation, reached at the end of growth phase, is exhibited by increase in sweetness, softness, colour and flavour development * Ripening happens due to natural physiological processes under enzymatic and hormonal control – Both physical and chemical changes in fruits * Senescence is the phase associated with deteriorative process, caused by aging, tissue death and associated with loss of quality (over-ripe and inedible)

Answer 53

* Ethylene is a plant hormone that plays key role in ripening and senescence of F & V * All plant cells produce low level of ethylene, but any external stress (wound, bacteria and fungi attack) can stimulate ethylene synthesis and release * Effect of ethylene on F & V – Chlorophyll is broken down, new pigments surface – Acids are broken down – fruit changes from sour to neutral to sweet – Amylase degrades starch to sugar – The breakdown of pectin between the the cells unglues them so they can slip past each other hence the softer fruit – Breakdown of large organic molecules to produce the aroma and tastes we associate with ripe fruit.

Answer 54

Climacteric fruits produce high level of ethylene during ripening – Exposure to exogenous ethylene may lead to acceleration of ripening and senescence • Non-climacteric fruit (e.g., citrus fruits) do not produce ethylene during ripening process but respond to exogenous ethylene by softening and increasing respiration rate – It does not promote natural ripening – In order to improve external skin colour and market acceptance, these fruits can be treated with ethylene, as a de-greening agent – Ethylene treatment breaks down the green chlorophyll pigment on the exterior part of the peel and allows the yellow or orange carotenoid pigments to be expressed

Answer 55

– Without careful temperature control, fruits will rapidly over-ripen and senesce – Failure to control respiratory heat also can increase water loss from the produce – Furthermore, the increased warmth and moisture levels developed during respiration may lead to increased bacterial and fungal infections --\> Temp needs to be controlled so this is slowed down!

Answer 56

Why are they changes in chlorophyll due to cooking of vegetables?

Answer 57

• Water loss – Structure and thus textural properties of fresh produce dependent on the moisture level inside the cells – If too much water is lost from the tissues wilting or wrinkling of the product will occur – The speed of post-harvest water loss is dependent primarily on the external vapour pressure • Other factors for water loss – Products with a large surface to volume ratio such as leafy crops will lose a greater percentage of water far quicker than large spherical fruits – Fruits with thick peels can lose a considerable amount of moisture from the skin without compromising edible quality (citrus species, bananas)

Answer 58

Fungal and bacterial growth – The most important microorganisms causing postharvest wastage of fresh produce are fungi – This is particularly true for fruits, where relatively acidic conditions tend to suppress bacterial growth – Vegetables with a higher pH can, however, suffer high losses from bacterial infections

Answer 59

– The most important cause of loss in fresh produce – The wound is an ideal entry point for many post-harvest pathogens – Physical injury stimulates ethylene production in plant tissues, which can lead to premature yellowing or ripening of commodities – Brown spots on over-ripe or injured bananas are due to over exposure to ethylene * Degradation of yellow pigments into brown * This is different from enzymatic browning of cut F & V due to PPO Cover the top of banaa with aluminum foil, not at much ethelyene will be converted. will ripen slower. Keep banana, pears and apples sepereate. Do not keep the different climacteric f and v together, will turn eachother

Answer 60

Precooling to remove field heat as quickly as possible after harvest. Essential for highly perishable products. ex) Icing, room or forced air cooling, hydrocooling (water)

Answer 61

– Many fruits and vegetables benefit from a surface coating which can slow down the loss of moisture – Coatings can also reduce the movement of gas in and out of the products – Many of the coatings applied are derived from plant extracts: carnauba, shellac or other natural waxes (for apples)

Answer 62

Irradiation- not allowed in Canada fro fresh f&v – Application of gamma ray or high energy electrons to fresh produce – Sprout inhibition in root, tuber and bulb crops – Control of some fungal diseases – Increased storage potential through delays to the ripening processes of fruits – In practice, very little fresh produce is actually irradiated owing to both these consumer concerns and legislative restrictions

Answer 63

Packaging where respiration can be controlled in many crops by reducing the levels of oxygen Can also be controlled by raising the levels of carbon dioxide. Packaging may also be conventional to reduce physical damage of sensative products.

Answer 64

Modified atmosphere packaging (MAP) by Polymeric films – Provide a barrier to the spread of decay from one unit to another – These films will also affect the movement of respiratory gases depending on the relative permeability of the film – This can lead to the development of lowered O2 and raised CO2 levels within the package – Reduce the respiration of the produce and potentially extend shelflife.

Answer 65

A modified atmosphere can be created within the pack in two ways: • Active modification involves the pulling of a slight vacuum within the pack and then replacing the atmosphere with the desired gas mixture – Absorbers of CO2, O2 or ethylene may be included within the pack to control the concentration of these gases. (force gas mixture into package) * In passive modification systems, the atmosphere is attained through the respiration of the products within the pack. (Passively by the respiration of the fruit and veg) * Temperature control is extremely important with MAP, as this will influence the gas permeability properties of the film as well as the respiration rate of the product

Answer 66

Primary packaging material remains in direct contact with the food Secondary packaging material may also be used for convenience, and protective purpose, and for printed material.

Answer 67

* Preservation * Protection against physical damage * Protection against chemicals, dirt and biological contamination * Aiding distribution to consumer * Create or enhance sales appeal (marketing)

Answer 68

• Gas permeability – OTR, oxygen transmission rate – WVTR, water vapor transmission rate * Protection against environmental factors (light, odor, microorganisms, moisture) * Mechanical properties (e.g., film strength, weight) * Reactivity with food (grease, acid, water, color) * Marketing-related (printability, cost) * Convenience (disposability, re-sealability)

Answer 69

Oxygen, carbon dioxide and nitrogen

Answer 70

Map is used to extend shelf life of red meat products * For fresh meats (ground beef), package may include high oxygen (80% O2 + 20% CO2) to maintain the red myoglobin pigment on meat surface * However, high oxygen level may lead to off colour and rancidity in cured meat and bacon. Therefore they are stored under vacuum * Pork, poultry meat has no requirement of O2 to maintain color, so they are stored under 90% CO2 to extend shelf life to 11 days * For cooked product, need to limit O2 to prevent oxidation so also could use vacuum packages

Answer 71

For fresh fruits and vegetables- minimize respiration and senescence without causing damage to metabolic activity... loss of quality • A typical modified gas composition for many fresh-cut fruits and vegetables: 2-5% O2, 8-12% CO2 and nitrogen – Reduces respiration rate, delay ripening and increase storage life (slow microbial growth). – But need some oxygen present to prevent anaerobic respiration/ fermentation and related negative biochemical changes * May need to control oxygen intake and CO2 release, as some product cannot handle excess CO2- Micro-Perforated films often used to regulate the internal atmosphere by using the natural respiration of fruits and vegetables * It is called “equilibrium MAP or eMAP”. The targeted Modified Atmosphere develops as an equilibrium steady state composition controlled by the modified permeability of the packaging film. * The required transfer rate of different gases through the packaging film is obtained by a properly designed microperforation pattern.

Answer 72

* MAP differs from Controlled Atmosphere (CA) storage which actively monitors and changes atmosphere around product (e.g., storage of apples) * CA utilizes low temperature storage in combination with specific concentrations of oxygen and carbon dioxide. Ethylene may also be controlled.

Answer 73

To help extend shelf life. Prevent lipid oxidation: acitve packaging containing antioxidant agents, radial scavengers, metal chelators and UV absorbers have been developed. To monitor freshness, how long product is stored Display information on quality. Detect temperature abuse. Improve safety. Antimicrobial film. Improve product convenience.

Answer 74

Help keep fruits and veggies fresh long by absorbing the ethylene that would have then overripening too soon.

Answer 75

Aluminum metalized sheet at bottom of package heats to about 400 degrees C and heats to food. "This side down" onto metal sheet.

Answer 76

Pack date – date of production * “Best before” or “best if used by” date. Last date of “Maximum” quality. Required when 90 days or less, also proper storage instructions must be given if not stored at room temp.Now some are trying “better if used by” * “Use by” or “expiration date”. date no longer can guarantee nutrition info on package. (e.g. baby foods) or reduced potency (e.g. drugs)

Answer 77

Canned good- BB is often 3 years after production, so 6-12 month more White flour- BB 6-12 months, so 6-8 months if pantry stored after opening

Answer 78

Sight, odor, touch, taste and sound

Answer 79

Aromas are volatile compounds, while we sense taste for non-volatile compounds

Answer 80

Odorant can reach the olfactory epithelium by two route: Orthonasal olfaction: The detection of an odor through the nostrils by sniffing or inhaling Retronasal olfaction: The detection of an odorant when it is released from food in your mouth during chewing, exhalation or swallowing. Some people lack or lose the ability to smell, This is called anosmia. Difference also exist in how sensitive people are to differnt odorant. Some people are more sensative to some odorant than other. Adaption to a specific smell also changes how we percieve a food

Answer 81

By our tongues, sensory organ of taste/ 1. Salt (NaCl) 2. Sour (lemon juice) 3. Sweet (sucrose) 4. Bitter (caffeine, alkaliods) 5. Umami (savory)- Action of trigeminal nerve's response due to the presence of glutamate (widely prensent in meat and fermented products) 95% of what we percieve as tatse is actually smell!!!!!!!!

Answer 82

Trigeminal nerves are responsible for sensation in the face and controlling how we chew and bite foods.

Answer 83

Supertasters Have strong good dislikes. Can detect specific ingredients in food samples. Have more intense reaction to various sensations ex) fat in food, more pain from oral irritants like capsaicin (pepper sensation). It is thought that "supertasters" are the people with a greater number of fungiform papillae. More of these taste buds makes you a supertaster

Answer 84

Medium tasters- tend to like all food, Are fussy about preparation. Think about food in a positive way Non-tasters- Attentive to presentation. May prefer higher sweeness to other groups. Think of food in terms of healthfulness rather than taste. Foods sensed more as a package (health and taste and presentation all coming together).

Answer 85

Subjective tests or Sensory evaluation * Determining preference to a particular product * Evaluating specific flavour or taste criteria of foods * May not be a subjective test if people are trained Objective tests • Laboratory methods and equipment to evaluate foods through physical and chemical tests

Answer 86

Discriminant tests Descriptive analysis affective/hedonic tests

Answer 87

Most complex and expensive of the techniques. Most food companies have a pannel that is trained on each of their products To train a panel takes several weeks to months The panelists are trained to evaluate products similar to how any insurment would give a reading. For example, a trained panel would be given a sample of grape juice and would be able to rate the level of tubrbidity, colour and viscosity. Answer on a ballot. Lots of stats are required to gather the information from the panelists.

Answer 88

Measuring the degree of liking for a food or its properties. Liking of the saltiness or sweetness? Best done by untrained panelists. Consumer panels- panelists should be representative of the target population for the product. 9-point scale (also referred to as the acceptance test)

Answer 89

Consumer-oriented companies have a reputation for product quality and permormance. Consitent quality is essenial for consumer perception of quality and is the basis for brand loyalty. Semsory evaluation is an important tool during the development of new products and its commercial launch. There are several key steps in developing a new commercial product

Answer 90

MOlecular gastronomy is a scientific discipline that studies the physicochemical tranformation of edible materials duing cooking and the sensory phenomena associated with eating them.

Answer 91

Hervé This in his book Molecular Gastronomy

Answer 92

Molecular gastronomy is a part of food science, it is the science of domestic or restaurant cooking. Food science is the use of physical sciecnes and engineering to study foods and understand their deterioration and the principles of food processing.

Food between farm gate and consumption Flashcards

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