Fruit Browning PDF

FRUIT BROWNING Browning The process of becoming brown, especially referring to food. Browning foods may be desirable, as in caramelization, or undesirable, as in an apple turning brown after being cut. a common colour change seen in food during pre-preparation, processing, or storage of food. I...

FRUIT BROWNING Browning The process of becoming brown, especially referring to food. Browning foods may be desirable, as in caramelization, or undesirable, as in an apple turning brown after being cut. a common colour change seen in food during pre-preparation, processing, or storage of food. It occurs in varying degrees in some food materials. The colour produced ranges from cream or pale yellow to dark brown or black, depending on the food item and the extent of the reaction. Browning reactions may be desirable or undesirable. In some food, the brown colour and flavour developed during browning is highly desirable and associated with a delicious, highly acceptable, and quality product. Browning reactions contribute to the aroma, flavour and colour of the product such as the browning crust of bread, and all baked goods, potato chips, roasted nuts, roasted coffee beans and many other processed foods. TYPES OF BROWNING A. Enzymatic browning (OXIDATIVE BROWNING) A chemical process, involving polyphenol oxidase, catechol oxidase, and other enzymes that create melanin and benzoquinone from natural phenols, resulting in a brown colour. occurs due to enzymatic browning, an oxidation reaction caused by exposure to oxygen. When fruit is cut or starts to break down, enzymes are released from the tissue and exposed to air, causing rapid color change Light-colored Fruits and vegetables darken when exposed to air as a result of the presence of oxidative enzymes. Enzymatic browning occurs in those fruits and vegetables when the cellular organization is disrupted by cutting, bruising or other injuries to the tissues. This is due to the action of oxidative enzymes on the presence of phenolic substances present in the fruit and vegetable tissues. Apples, Banana, Pears, Brinjals and potatoes undergo enzymatic browning. Enzymatic browning takes place only in fruits and vegetables which contain phenolic compounds. These phenolic compounds act as the substrate, and in the presence of oxygen and by the action of enzymes, the following oxidative reaction is observed In general, enzymatic browning requires exposure to oxygen For example, the browning that occurs when an apple is cut. Another example is the skin of a banana. BENEFITS OF ENZYMATIC BROWNING 1. Developing flavour in tea 2. Developing colour and flavour in dried fruit such as figs and raisins. 3. Enzymatic browning is often detrimental to: 4. Fresh fruit and vegetables, including apples, potatoes, bananas and avocados 5. Seafood such as shrimp 6. A variety of techniques for preventing enzymatic browning exist, each exploiting a different aspect of the biochemical process. 7. Lemon juice and other acids lower the pH and remove the copper cofactor necessary for the responsible enzymes to function 8. Blanching or roasting, to denature enzymes and destroy responsible reactants, as used in the "kill green" phase of tea processing 9. Low temperatures can also prevent enzymatic browning by reducing the rate of reaction. 10. Inert gas, like nitrogen, prevent necessary oxygen from reacting 11. Chemicals such as sodium bisulfite and citrates B. NON-ENZYMATIC BROWNING A chemical process that produces a brown color in foods without the activity of enzymes. can occur through two forms: caramelization and Maillard reaction. Unlike enzymatic browning, non-enzymatic browning does not involve enzyme activity. Caramelization occurs when carbohydrates or sugars in food are heated. The Maillard reaction is a protein-sugar interaction that leads to the development of brown color in a mixture containing amino acids and reducing sugars. Two main forms of non-enzymatic browning A. Caramelization B. Maillard Reaction A. Caramelization ➤ The pyrolysis of sugar. ➤ when sugar is heated at high temperature (160 deg C) in the absence of water and amino acids, it turns brown and this sugar-sugar interaction is known as caramelization.Sugar is broken down into a number of compounds due to intense heat. sucrose caramel + acid ➤ It is used extensively in cooking for the resulting nutty flavor and brown color. ➤ As the process occurs, volatile chemicals are released, producing the characteristic caramel flavor. development of caramel flavour and colour in caramel custard is a desirable change, whereas uncontrolled heating of sugar can lead to objectionable burnt colour and flavour. B. Maillard reaction ➤ A chemical reaction between an amino acid and a reducing sugar, usually requiring the addition of heat. ➤ The sugar interacts with the amino acid, producing a variety of odors and flavours. ➤ It is a protein-sugar interaction. It leads to the development of brown colour in a mixture containing amino acids and reducing sugars. It is also called carbonyl- amine reaction. ➤ The brown colour formed contributes to the aroma, flavor, and colour of many ready to eat cereals, baked food, malted barley etc. various factors which affect this reaction are-type of sugar- the more percentage of reducing sugar, the darker the crust in the bakery products, type of amino acid, temperature, moisture. ➤ The Maillard reaction is the basis of the flavouring industry, since the type of amino acid involved determines the resulting flavor; it also produces toast. Maillard reaction also leads to undesirable changes like unfavourable brown colour eg. In dried milk. Detrimental flavour changes eg. Burnt flavour. ➤ Example: A. The Crust of Brioche Bread: which is golden-brown. B. The wine color is altered with wine aging by reactions between different active molecules present in the wine, these reactions, in general, giving rise to a browning of the wine, leading from red to a more tawny color. Melanoidins ➤ Are brown, high molecular weight heterogeneous polymers that are formed when sugars and amino acids combine (through the Maillard reaction) at high temperatures and low water activity. ➤ Melanoidins are commonly present in foods that have undergone some form of non-enzymatic browning ➤ Example: A. Barley malts (Vienna and Munich), bread crust, bakery products and coffee. B. Wastewater of sugar refineries, necessitating treatment in order to avoid contamination around the outflow of these refineries. Reaction of oxidation products- A. ascorbic acid browning Ascorbic acid browning- Ascorbic acid present in fruits undergo oxidation with the formation of a compound which produces a brown pigment and causes discolouration. This type of browning is seen in preserves. Low storage temp can help in retarding the reaction. B. lipid browning Lipid browning-many fatty foods during processing and storage exhibit browning which can be attributed to the reaction of lipid oxidation products with amino acids, amines and proteins. For eg.white fish containing PUFA and high concentration of protein shows discolouration in muscle during frozen storage Differentiate between Ripe and Unripe Fruits 1. UNRIPE FRUITS ➤ Contain more complex forms of carbohydrates/sugar than what the body should digest. ➤ They also contain resistant starches of similar function to the fiber content in ripened fruits, ➤ Makes it harder for the body to digest unripe fruits, so your digestive tract may give warning signs. ➤ Unripe fruits that you keep at home for a few days before consumption; such as bananas and mangoes. 2. RIPE FRUITS ➤ Have a more tender fiber texture. ➤ Definitely higher as the carbohydrate content keeps breaking into sugars so long the fruit is on the tree. ➤ As certain that ripe fruits develop a higher content of minerals as they get them from the water and elements in soil so long the fruit is on the tree. ➤ A better development of antioxidant flavonoids with the appropriate chemical change occurring with mineral supply from the soil "Example: green bananas are not the same as bananas just before turning black. The texture becomes too tender and it is almost like eating sugar CHEMICAL ANALYSIS OF URINE The routine urinalysis includes chemical testing for pH, protein, glucose, ketones, occult blood, bilirubin, urobilinogen, nitrite, leukocyte esterase, and strip test method for specific gravity. The urinalysis offered by laboratories depends on the type of dipstick that is used A urinalysis is a set of tests on your pee (urine). You provide a urine sample, either in a cup or with a catheter. Then your provider sends it to a lab for a visual exam, dipstick test and microscopic exam. You might need a urinalysis as part of a routine screening or if you have symptoms of an infection, diabetes, or kidney or liver issues. A urinalysis is a set of tests that looks at the appearance of your pee (urine) and checks for blood cells, proteins and other substances in it. Your provider might use it as a routine screening test or to look for signs of infection, kidney or liver disease, diabetes or other health conditions. Visual exam A healthcare professional looks at the color, clarity and anything else they see with the naked eye in a visual exam. The description might include: Color. Normal pee color is usually some shade of yellow and can range from colorless or pale yellow to deep amber. This can depend on how concentrated or diluted (watery) your pee is. Clarity. They'll note if your pee is clear or cloudy. They may also describe it as turbid (thick with suspended substances). Reagent strip (also called a dipstick,) ➤ A narrow strip of plastic with small pads attached to it. ➤ Each pad contains reagents for a different reaction, thus allowing for the simultaneous determination of several tests ➤ Dipsticks are plastic strips with patches of chemicals that change color when they touch certain substances.: The degree of color change on a test pad can also give an approximation of the amount of substance present. For example, a slight color change in the test pad for protein may indicate a small amount of protein present in the urine whereas a deep color change may indicate a large amount. Some reagent test strips also have a test pad for ascorbic acid [vitamin C). Indication for URINALYSIS As part of a routine medical exam to screen for certain health conditions. If you're experiencing symptoms of an infection, kidney disease or diabetes. To monitor certain health conditions. During pregnancy. If you've been admitted to a hospital. In preparation for surgery PREPARATION Usually, you don't have to do anything to prepare for a urinalysis. You may need to drink an extra glass of water if you don't feel like you'll be able to pee for the test. But drinking too much extra water can give inaccurate results. Let your provider know:  If you're currently getting your period (menstruating). Menstrual blood and vaginal discharge can interfere with certain urinalysis test results. If you have trouble peeing away from home, or shy bladder syndrome. They can give you options for providing a sample that'll be comfortable for you. In certain circumstances, your provider might ask you to: Get the sample from your first pee in the morning. Avoid certain foods before the test. Stop taking certain medications that can affect the results. Only stop taking medications if your provider tells you to. IN COLLECTING URINE healthcare provider's office or at a laboratory using the "clean catch" method. You or your healthcare provider can also collect a urine sample using a catheter (thin tube). For the clean catch method, your provider will give you a specimen cup, sterile wipes and specific instructions for collecting your urine sample. Your provider will tell you what to do with your sample after you've collected it. It's important to wash your hands with soap and water before you collect the sample. Collecting a clean catch urine sample IN FEMALE collect your pee with the following steps: 1. Start by sitting on the toilet with your legs spread apart. 2. Using two fingers, spread your labia open. Use one sterile wipe to clean the inner folds of your labia, wiping from front to back. 3. Use another sterile wipe to clean the opening to your urethra, where pee flows out of your body. 4. Pee a small amount into the toilet. 5. Stop the flow of pee and hold the specimen cup a few inches away from your urethra. 6. Pee into the cup until it's about halfway full or to the amount your provider recommends. It's OK if you can't fill it quite halfway. 7. Finish peeing into the toilet (if you need to). Collecting a clean catch urine sample IN MALE ⚫ collect your pee with the following steps: 1. Use a sterile wipe to clean the head of your penis. If your penis is uncircumcised, first pull back your foreskin to ensure a thorough cleaning. 2. Pee a small amount into the toilet. 3. Stop the flow of pee and hold the specimen cup below your penis. 4. Pee into the cup until it's about halfway full or to the amount your provider recommends. It's OK if you can't fill it quite halfway. 5. Finish peeing into the toilet (if you need to). Collecting a urine sample with a catheter A healthcare provider can also collect a urine sample with a catheter. They'll clean the area around the opening of your urethra with a germ-killing (antiseptic) solution and insert a catheter into your urethra. Your pee will drain into a sterile container and your provider will remove the catheter. The most frequently performed chemical tests using reagent test strips are: 1. Specific gravity 2. pH 3. Protein 4. Glucose 5. Ketones 6. Blood 7. Leukocyte esterase 8. Nitrite 9. Bilirubin 10. Urobilinogen 1. Specific Gravity (SG) ➤ The first test, that is actually a physical characteristic of the urine ➤ A measure of urine concentration that can be determined using a chemical test. ➤ There are no "abnormal" specific gravity values. ➤ This test simply indicates how concentrated the urine is. ➤ Specific gravity measurements are actually a comparison of the amount of solutes (substances dissolved) in urine as compared to pure water. ➤ If there were no solutes present, the SG of urine would be 1.000 - the same as pure water. ➤ Since all urine has some solutes a urine SG of 1.000 is not possible. ➤ If a person drinks excessive quantities of water in a short period of time or gets an intravenous (IV) infusion of large volumes of fluid, then the urine SG may be as low as 1.002. ➤ The upper limit of the test pad, an SG of 1.035, indicates concentrated urine, one with many solutes in a limited amount of water. ➤ Knowing the urine concentration helps health care providers decide if the urine the specimen they are evaluating is the best one to detect a particular substance. ➤ For example, if they are looking for very small amounts of protein, a concentrated morning urine specimen would be the best sample. 2. pH ➤ As with specific gravity, there are typical but not "abnormal" pH values. ➤ The kidneys play an important role in maintaining the acid-base balance of the body. ➤ Therefore, any condition that produces acids or bases in the body such as acidosis or alkalosis, or the ingestion of acidic or basic foods, can directly affect urine pH. ➤ Diet can be used to modify urine pH. ➤ A high-protein diet or consuming cranberries will make the urine more acidic. ➤ A vegetarian diet, a low-carbohydrate diet, or the ingestion of citrus fruits will tend to make the urine more alkaline. ➤ Some of the substances dissolved in urine will precipitate out to form crystals when the urine is acidic; others will form crystals when the urine is basic. ➤ If crystals form while the urine is being produced in the kidneys, a kidney stone or "calculus" can develop. ➤ This measures the acid-base (pH) level in your pee. Kidney issues and urinary tract infections (UTI) can cause high urine pH. Diabetes-related ketoacidosis and diarrhea can cause low urine pH. ➤ By modifying urine pH through diet or medications, the formation of these crystals can be reduced or eliminated. 3. Protein ➤ The protein test pad measures the amount of albumin in the urine. ➤ Other proteins are not detected by the test pad but may be measured with a separate urine protein test. ➤ Normally, there will not be detectable quantities. ➤ This measures the presence of proteins, like albumin, in your pee. Heart failure, kidney damage (often from high blood pressure or diabetes), overexertion and dehydration can lead to elevated protein levels. Proteinuria; ➤ When urine protein is elevated ➤ This can be an early sign of kidney disease. Albumin ➤ Smaller than most other proteins and is typically the first protein that is seen in the urine when kidney dysfunction begins to develop. Other conditions that can produce proteinuria include: 1. Disorders that produce high amounts of proteins in the blood, such as multiple myeloma 2. Conditions that destroy red blood cells 3. Inflammation, malignancies (cancer), or injury of the urinary tract - for example, the bladder, prostate, or urethra 4. Vaginal secretions that get into urine 4. Glucose ➤ Glucose is normally not present in urine. ➤ A glucose urine test measures the amount of sugar (glucose) in your urine. Diabetes or gestational diabetes can cause glucose in your pee. Glucosuria ➤ When glucose is present in the urine. ➤ It results from either: A. Uncontrolled diabetes mellitus ➤ An excessively high glucose concentration in the blood B. A reduction in the "renal threshold." ➤ When blood glucose levels reach a certain concentration, the kidneys begin to excrete glucose into the urine to decrease blood concentrations. ➤ Sometimes the threshold concentration is reduced and glucose enters the urine sooner, at a lower blood glucose concentration. Some other conditions that can cause glucosuria include: 1. Hormonal disorders, 2. Liver disease 3. Medications 4. Pregnancy. When glucosuria occurs, other tests such as blood glucose are usually performed to further identify the specific cause. 5. Ketones ➤ Ketones are not normally found in the urine. ➤ Healthcare providers most often use ketone urine tests to check for diabetes- related ketoacidosis. ➤ They are intermediate products of fat metabolism. ➤ They can form when a person does not eat enough carbohydrates (for example, in cases of starvation or high-protein diets) or when a person's body cannot use carbohydrates properly. When carbohydrates are not available, the body metabolizes fat instead to get the energy it needs to keep functioning. ➤ Ketones in urine can give an early indication of insufficient insulin in a person who has diabetes. ➤ Severe exercise, exposure to cold, and loss of carbohydrates, such as with frequent vomiting, can also increase fat metabolism, resulting in ketonuria. KETONURIA ➤ Present of ketones in urine 6. Blood (Hemoglobin) ➤ This test is used to detect hemoglobin in the urine (hemoglobinuria). ➤ Hemoglobin is an oxygen-transporting protein found inside red blood cells (RBCs). ➤ Liver or bile duct issues can lead to bilirubin in your pee. ➤ Blood (hemoglobin). Infections, damage in your urinary tract, high blood pressure and cancer can cause blood in your pee (hematuria). Hematuria ➤ Its presence in the urine indicates blood in the urine ➤ The small number of RBCs normally present in urine. (See microscopic examination) usually results in a "negative" test. ➤ However, when the number of RBCs increases, they are detected as a "positive" test result. ➤ Even small increases in the amount of RBCs in urine can be significant. ➤ Numerous diseases of the kidney and urinary tract, as well as trauma, medications, smoking, or strenuous exercise can cause hematuria or hemoglobinuria. ➤ This test cannot determine the severity of disease nor be used to identify where the blood is coming from. ➤ For instance, contamination of urine with blood from hemorrhoids or vaginal bleeding cannot be distinguished from a bleed in the urinary tract. ➤ This is why it is important to collect a urine specimen correctly and for women to tell their health care provider that they are menstruating when asked to collect a urine specimen. ➤ Sometimes a chemical test for blood in the urine is negative, but the Microscopic Exam shows increased numbers of RBCs. When this happens, the laboratorian may test the sample for ascorbic acid (vitamin C), because vitamin C has been known to interfere with the accuracy of urine blood test results, causing them to be falsely low or falsely negative. 7. Leukocyte Esterase ➤ Leukocyte esterase is an enzyme present in most white blood cells (WBCs). ➤ Normally, a few white blood cells (see microscopic examination) are present in urine and this test is negative. ➤ Leukocyte esterase is an enzyme that helps you fight infections. If a leukocyte esterase test is positive, you might have inflammation in your urinary tract, most often caused by a UTI. ➤ When the number of WBCs in urine increases significantly, this screening test will become positive. ➤ When the WBC count in urine is high, it means that there is inflammation in the urinary tract or kidneys. ➤ The most common cause for WBCs in urine (leukocyturia) is a bacterial urinary tract infection (UTI), such as a bladder or kidney infection. 8. Nitrite ➤ This test detects nitrite and is based upon the fact that many bacteria can convert nitrate to nitrite in the urine. ➤ Normally the urinary tract and urine are free of bacteria. ➤ When bacteria find their way into the urinary tract, they can cause a urinary tract infection (UTI). A positive nitrite test result can indicate a UTI. ➤ However, since not all bacteria are capable of converting nitrate to nitrite, someone can still have a UTI despite a negative nitrite test. 9. Bilirubin ➤ Bilirubin is not present in the urine of normal, healthy individuals. ➤ Bilirubin is a waste product that is produced by the liver from the hemoglobin of RBCs that are removed from circulation. ➤ It becomes a component of bile, a fluid that is secreted into the intestines to aid in food digestion. ➤ In certain liver diseases, such as biliary obstruction or hepatitis, bilirubin leaks back into the bloodstream and is excreted in urine. ➤ The presence of bilirubin in urine is an early indicator of liver disease and can occur before clinical symptoms such as jaundice develop. 10. Urobilinogen ➤ Urobilinogen is normally present in urine in low concentrations. ➤ It is formed in the intestine from bilirubin, and a portion of it is absorbed back into the bloodstream. ➤ Positive test results help detect liver diseases such as hepatitis and cirrhosis and conditions associated with increased RBC destruction (hemolytic anemia). ➤ When urine urobilinogen is low or absent in a person with urine bilirubin and/or signs of liver dysfunction, it can indicate the presence of hepatic or biliary obstruction. Normal urinalysis results. Normal ranges for values on your urinalysis can vary some, but in general, they include: Test 1. Color Normal value. Yellow 2. Clarity Normal value Clear or cloudy 3. Bilirubin Normal value. Negative 4. Glucose Normal value Negative or trace 5. Hemoglobin/blood Normal value Negative or trace 6. Ketones Normal value Negative, none or trace 7. Protein Normal value. Negative or trace 8. Leukocyte esterase Normal value Negative or trace 9. Nitrite Normal value Negative 10. Urine pH. Normal value :5.0 - 8.0 11. Urine specific gravity Normal value: 1.005 1.030 12. Bacteria Normal value None or negative 13. Casts Normal value 0/LPF (low powered field) 14. Urine RBC Normal value 0-3/HPF (high powered field) 15. Urine WBC Normal value 0-5/HPF 16. Yeast Normal value None or negative