0:15 Hello all. Uh this is Nanita Krishnan working as lecturer in the department of clinical nutrition Sri Ram Chandra faculty of allied health sciences at Shriram Chundra Institute of Higher Education and Research. The topic that I'll be dealing with is introduction to food spoilage and preservation. So food spoilage is nothing but type of food deterioration that happens because of uh certain processes like enzyatic chemical etc. which can lead to deterioration of foods texture, palatability and nutritional value because of the presence of microorganisms. So the objectives of the topic will be to explain the main causes and prevention of food spoilage
1:03 to interpret the types of food spoilage and to outline the principles of food preservation. So moving on to the introduction of the topic. So food is defined as any material which consists of macronutrients like protein, carbohydrate and fat which can be used by the body of an organism in order to sustain the growth, repair and vital processes in order to furnish the energy. So food contains various essential nutrients which can be contaminated by microorganisms. So there are two types of contamination of which one is natural contamination and the other one is artificial
1:49 contamination. Natural contamination is nothing but uh the presence of certain insects because of which microorganisms can be prone into the food. The same way artificial contamination is because of the exposure to environmental factors such as uh industrial uh wastes um and then uh chemicals that can be exposed to food because of which food becomes harmful for consumption. So food spoilage the definition is in food several kinds of chemical changes can occur once the food is harvested. So these changes may be considered desirable. So the changes include meat tenderizing uh so which can actually be
2:39 safe for consumption. But food deterioration happens when there is a growth of microorganism. Because of the time food can be uh reduced in its uh texture and palatability. Moisture loss can also deteriorate the foot and then microorganisms build up like bacteria, virus, fungi, yeast etc. and exposure to various environmental factors as I told you and then also because of inappropriate uh food preparation methods.
3:25 So there are various classes of food changes which can be seen. First one is the enzyatic process which includes uh the change that is underwent by the flesh of the animal. So the changes include proteolyis wherein the own enzymes will have a death that happens after the harvest and this can undergo a type of change which is the enzyatic process. So harvested crop there will be a rapid breakdown of starch and because of which there will be a sugar depletion happening. So this is one kind of a food spoilage. Uh so what are the enzymes which can cause food spoilage. So the first enzyme is
4:10 ascorbic acid oxidase which is present in vegetables. So this will destruct the vitamin C present in the food. Then comes lipase which is present in milk and oils. So this will have an hydraytic rancidity happening in the food. Then lipoxygenase is present in vegetables which will actually destract the vitamin A components of food. Then pectic enzymes which are present in fruits will destruct the pectic substances which will actually soften the fruits. and then peroxidasis which will cause browning of fruits. Coming to the chemical reactions which are present in the food. So chemical
5:00 reaction basically happens due to environmental factors like abiotic chemical reaction that involves oxidation of the food by air. So lipid auto oxidation can generate rancid orders. Rancidity is nothing but an old kind of ador that can be present in fats and oils when it is being recycled. Uh so this is one kind of a food spoilage process. Then comes microbiological processes wherein a food gets contaminated by the wide range of microbial substances that are present in the uh environment. So an example of uh chemical reaction and a microbiological process wherein yeast or a mold uh pathogen is present in the bread.
5:55 So coming to food spoilage it refers to the microbiological changes which render a product unfit or unpalatable for consumption. So most footsteps serve as grow good media for the growth of many different microorganisms. So once the microorganism grows there will be a change in the appearance, flavor, order and nutritional value of food. So food spoilage is nothing but uh a food is unsafe for consumption because of the palatability changes and the loss of nutritional value. So what happens in different uh uh foods? Basically temperature, pH, enzyatic processes uh and the peptide
6:44 bonds are all depleted or destructed because of various microorganisms production in the food. Process of food spoilage. So there are various degradation process that can happen in foot which can cause the foot spoilage. First one is putrifaction which is nothing but protein foots gets degraded because of the uh presence of microbes. So protein foods in addition with proteolytic microbes can cause depletion in the amino acids and breakdown of amino acids. Um and then comes fermentation wherein carbohydrate foods will have the
7:31 presence of carbohydrate fermenting microbes such as yeast which can deplete the uh food consumption or it becomes unsafe for consumption. Third one is the rancidity which is nothing but the fatty foods are being uh deteriorated because of the rancid producing orders. So this happens because of lipolytic microbes present in fatty acids and glycerol. So different food gets spoiled in different uh action or mode. Uh so this will actually cause nutrient depletion and microbial species also will be present because of the environmental factors such as temperature. So for example, there will be germs that can attack a fresh apple and because of
8:20 which there will be gases that we produce. So basically yeast is one of the microorganisms that can be deteriorating the characteristics of apple because it is a carbohydrate rich food and fermentation happens. So this will emit gases and it will destroy the apple's palatability. So what are the food groups and the nutrients that are responsible for the uh presence of micrllora? This is the slide. So diary products will have protein degradation happening and this can actually uh contribute to the presence of streptos caucus and salmonella species. Coming to meat and
9:08 poultry, it will have fatty acid oxidation happening in them and this will lead to breakdown of microorganisms. So this can contribute to the growth of sudona species and salmonola species. Then coming to seafood there is a breakdown of amino acid nothing but the building block of protein. So this will lead to the growth of sudamona species and lististeria species in seafood. Coming to plant food, there is fermentation of carbohydrates happening as shown in the previous slide. There'll be gases that will be emitted and that can lead to uh reduction in the consumption quality of plant foods. So risopus species and Canada species are certain examples of
9:53 the growth of microorganisms present in plant foods. So these microbes can actually cause uh becomes unsafe for consumption when these microorganisms are present in the foods and this can lead to various health effects like nausea, constipation, diarrhea and stomach disturbances. So what are the microbes that are present in food? Yeast is basically present in high sugar such as carbohydrate rich foods. Bacteria is present in low acid foods. Molds are present in high acid foods and fungi will be present in moisture based foods. Like presence of high moisture can cause uh the buildup of fungi in foods. Coming to food preservation.
10:46 So in order to prevent the spoilage of food, there is a technique called as preservation which can be uh done with the foots. So food preservation is nothing but it is a process of treating and handling food in order to stop or slow down the spoilage that can be caused or accelerated by microorganisms. So preservation technique usually involves the prevention of pathogens or microorganisms that can the oxidation of fats which can cause rancidity. So coming to the principles of food preservation.
11:31 So first one is prevention or delay of microbial decomposition. So this involves keeping out microorganisms aseptic environment and then removal of microorganisms and this will also hinder the growth and activity of microorganisms by bringing the food to low temperature drying anorobic conditions. Nothing but removal of oxygen or the oxygen will not be involved in these temperatures or chemical usage. And then microorganisms can also be killed by heat radiation. So prevention or delay of microbial decomposition comprises of four methods wherein aseptic environment will be
12:19 followed. Microorganism removal, growth and activity of microorganisms is hindered and microorganisms can be killed by techniques like radiation. Second one is self decomposition uh activity will be followed wherein there'll be a inactivation of food enzymes that can be present in the uh technique. So example can include blanching and then chemical reactions can also be delayed by the use of antioxidants. So self decomposition method include two things of which one is inactivation of food enzymes and the second one is delaying of chemical reaction. So food
13:06 enzyme inactivation can happen with the help of pro food methods like blanching which is a moist heat method and then delaying of chemical reaction can happen with the help of antioxidants like vitamin A, vitamin C, vitamin E or selenium being added to the food. So food preservation will help in delaying the microorganism presence. It will prevent the uh accumulation of microorganisms and can also help in reducing the enzyatic processes happening in the food. So key takeaways of this unit include various causes of food spoilage like enzyatic processes, chemical reactions
13:55 and microbiological reactions that can happen in food which can deteriorate the food's quality. So enzyatic processes include browning or uh protein degradation and then chemical processes include uh the fermentation process that can actually cause uh the uh deterioration of food and microbiological processes like the presence of microbial species in each of the food groups because of uh the nutrient degradation. and then the process of food spoilage wherein food sources, nutrients and micro species are involved uh in the deterioration of food uh consumption. So these food sources are depleted by uh processes such as putrifaction,
14:44 rancidity and uh fermentation processes of which putrifaction will happen in protein richch foods. uh fermentation will happen in carbohydrate rich foods and rancidity will happen in fat uh rich foods. Uh so carbohydrates in the sense high sugars can cause the presence of yeast growing in the uh food products and then putrifaction will be because of protein degradation whereas rancidity will happen because of oxidation of fatty acids. Then we also dealt with principles of food preservation uh which includes the uh deactivation of microorganisms hindering the growth and activity of microorganisms basically microorganism deactivation or
15:32 inactivation process and then the second is self decomposition method wherein antioxidants like vitamin A, C or citric acid components are added to the foots in order to prevent the growth of microorganisms and The other uh process is uh usage of pro proper and accurate methods of cooking like blanching which can actually hinder the inactivation of which can actually uh prevent the enzyme being formed in the food and browning can be prevented.
