Where did the Western Diet Start? • 10 000 years ago • Introduction of agriculture and Food Engineering • Introduction of animal husbandry
New Food Stuff • 70% of our daily energy intake was unavailable prior to the industrial revolution • Refined sugar • Refined vegetable oil • Cereals • Diary products • Alcohol • Mixed foods, Canned Foods, Frozen Foods • Cookies, pizza, soft drinks, ice cream...etc!!!!
Lets Look at Unit Operations and Consequences? • Simplest Unit Operation • Size Reduction • Increased Functionality i.e., starch from granule • Increased shelf life i.e. sugar from sugar cane • Used as ingredients i.e., vegetable oils
Milling • Separate the endosperm from the bran and germ 3.5% of our energy is from whole grains 20.4% of our energy is from refined grains
Refined Sugar • Crystalline sugar 500BC • Pre 500BC honey was consumed • Typical consumption <1kg per capita • Post industrial revolution 6.8kg per capita • Currently 69kg per capita • Now there is high fructose corn syrups and other artificial sweeteners
Refined Sugars • Average American consumes 2-3 pounds of sugar each week • One of sugar's major drawbacks is that it raises the insulin level, which in turn depresses the immune system. • This is not something you want to take place if you want to avoid disease.
Refined vegetable oils • From 1909 to 1999 • 130% increase in the consumption of salad and cooking oils • 140% increase in the consumption of shortening • 410% increase in the consumption of margarine
2nd Unit Operation -- Hydrogenation • Produce what was thought to be novel trans fatty acid isomers • Trans elaidic acid only occurs in hydrogenated food stuff • One of the food industries largest mistakes.
Thermal Processing • Commonly applied during food processing • Severity of the process (amount of heat applied) is a function of both time and temperature • This minimizes nutrient loss • Minimizes reduction in product quality • Minimizes energy consumption
Thermal Processing • Most widely applied unit operation in food processing • Fundamental aspects • Involves the application of heat • Amount of heat added is a function of time and temperature • Preservative effects largely due to denaturation of protein
Types of Thermal Processing • Cooking • Blanching • Pasteurization • Sterilization
Cooking • Primary objective: to increase palatability • Baking, roasting - dry heat, 150-200°C • Boiling, stewing, steaming - boiling water to steam (~100°C) • Frying with or without oil, 175 to 225°C • Some preservative changes • Destruction of some spoilage and all pathogenic microorganisms • Inactivation of deteriorative enzymes • Reduction of water
Cooking • Other desirable changes • Inactivation of some anti-nutritional factors • avidin in egg white which binds biotin (B7) • hemagglutinins in kidney and wax beans • agglutination of red blood cells • Improved digestibility of some food constituents
Cooking • Undesirable changes • Loss of nutrients • Oxidation of unsaturated lipids • Degradation of antioxidants • Decline in sensory quality with excessive heating • Non enzymatic Browning—toast and maple syrup
Nutrient Loss • Lysine bio -availability reduced by non-enzymatic browning • Heat sensitive vitamins—decreases bioavailability not concentration • Vitamin A, Carotenes, Vitamin D • Water leaching vitamins-decreases concentration not bioavailability • Thiamine, Niacin, Folate,
Blanching • Prior to drying of fruits • Primary objective • Inactivate deteriorative enzymes • Also kills some spoilage bacteria (reduces microbial load) • Commercially • Atmospheric steam or boiling water (~100°C) • Pressurized steam or hot gas (>100°C) • Less severe process than canning for example
Water Vs Steam Blanching • Steam blanching has little to no leaching of nutrients
Blanching • Blanching prior to freezing • Blanching of vegetables prior to canning • Removes tissue gases • Cleanses tissue, wilts tissue • Blanching of fruits before drying • Surface pasteurization to extend shelf life • Drying conditions may not destroy enzymes
Blanching • Losses mainly due to: leaching, thermal destruction, oxidation • Amount of losses depend on: • Type of food • Extent of particle size reduction • Ratio of surface area to volume • Time / temp • Heating and cooling medium • Leaching greater in water than steam or air • Ratio water to food
Pasteurization • A heat treatment which kills part of the microbial population present in a food • Min changes in sensory or nutritive value • Pasteurization of milk • Primary objective is to kill pathogenic micro-organisms; shelf life is extended due to a reduction in spoilage organisms, deteriorative enzymes • Target pathogens: was Mycobacteriumtuberculosis (TB), now Coxiellaburnetti (Q fever)
Mycobacterium tuberculosis • Are found in infected cattle worldwide. • These organisms are destroyed by pasteurization. • Cause tuberculosis, a lung disease. • Tuberculosis in the US is not very common today, although historically milk was a common source of tuberculosis.
Coxiella burnetii • The prevalence of Coxiella burnetii was >94% in raw milk samples from the Northeastern, Midwestern, and Western regions of the US tested between 2001 and 2003
Pasteurization • Two equivalent processes in terms of microbial kill • LTH (low temp, hold) = 63°C for 30 min • HTST (hi temp, short time or flash) = 72°C for 15 sec • However, LTH is more detrimental to nutritional and sensory properties • Don’t drink raw milk - • Other pathogens - Ontario study (1997) Listeria monocytogenes, salmonella, Verotoxogenic E. coli.
Pasteurization • Beer • Intention to kill spoilage organisms- primarily wild yeasts, gives a shelf life of 6 months for bottled beer vs 1 month for draft • Juices • Eggs - recommended that pasteurized eggs be used for salad dressings and sauces to kill salmonella • Can now do “in shell”
Sterilization • A heat treatment sufficient to destroy ALL microorganisms capable of growth under the conditions of storage • This is not true sterility as some nonpathogenic spore forming bacteria may eventually grow under optimum conditions • Severity of the process required for safety and shelf stability is dependent on the acidity of the food product being canned. • Low-acid foods (pH > 4.5) • Acid foods (pH 3.7 to 4.5) • High-acid foods (pH < 3.7)
Low Acid Foods (pH 4.5) • Most severe process is needed for low-acid foods • Clostridium botulinum will grow and produce toxin in foods at pH 4.6 or greater • Spore-forming, obligate anaerobe, ubiquitous • Canning of low acid foods (pH > 4.5) • meats, fish, vegetables, mixed entrees, most soups • Need to process at 121°C for ~15 min. • How do we get water to boil at 121°C rather than 100°C?
High Acid Foods (pH 4.5) • Fruit jams, fruit cocktail, tomatoes*** and tomato juice***, peaches, vegetable juice • Primary target - facultative anaerobes (Bacillus spp). • Can use milder process • do not need to pressure can, can process at 100°C • Must make sure tomatoes are acidic enough • Boiling water bath at atmospheric pressure is sufficient
High Acid Foods • Apple juice, cider, berries, citric juices, sour pickles, sauerkraut • Targets are yeast and molds • Anaerobic bacteria won’t grow, so can use a milder process for spores of yeasts and molds. • Can “hot fill” containers at ~90°C • Should also invert to heat the lid, volume change on cooling will create slight vacuum
Factors Influencing Severity • Severity of thermal process required to produce commercial sterility depends on: • Nature and heat resistance of the microbes present • Initial microbial load • Nature of the food (e.g. pH, chemical composition, water activity…) • Conditions of storage
First Order Kinetics • Most biological inactivation processes (e.g., enzyme denaturation, microbial death, spore deactivation) are a function of both time and temperature • Effect of Time: usually follows first-order kinetics:
Thermal Resistance • Death rate of microorganisms is logarithmic • In a given time interval, at a constant temperature, the same proportion of a microbial population will be destroyed
Pasteurization: • 7 log kill for Salmonella in Milk = 99.99999% • Pasteurization of eggs: 3 log reduction = 99.9% 145°F for 3 to 4 mins. • Fruit juices are pasteurized to reduce microbial count and inactivate enzymes; they were thought not to carry pathogens. Temperature: 145°F (63C) 161°F (72C) 212°F (100C) 280°F (131C) Time: 30 min 15 sec 0.01sec 6 sec
Mild vs. Severe Heat Treatment: • Mild Heat Treatment): • Aims: • Kill pathogens • Reduces bacterial load (Food is not sterile) • Inactivate enzymes • Advantages: • Minimal damage to flavor, texture, and nutritional quality. • Disadvantages: • Short shelf life • Another preservation method must be used, such as refrigeration or freezing • Examples: • Pasteurization • Blanching • Severe Heat Treatment: • Aims: • Kills all bacteria • Food will be commercially sterile • Advantages: • Long shelf life • No other preservation method is necessary • Disadvantages: • Food is over-cooked • Major changes in texture, flavor, and quality • Examples: • Canning
Unit Operations • Almost all unit operations reduce quality • Milling • Evaporation • Cooking • Pasteurization • Irradiation • However we see benefits • Convenience, supply and demand, microbial safety,
Food for Thought Western countries single largest cause of morbidity and mortality are diet-related chronic diseases!!!!
Food for Thought 50-65% of the western adult population are afflicted with a diet related disease.
Food for Thought Food related disease do not steam from a single element of food consumption, but rather from a complex interaction of multiple nutritional factors.