It's very informative. Great Mam. I want to make sugarcane juice with 2 month shelf life. If you have more information on that kindly share it. Thanks
@parthasarathyarumugam11814 ай бұрын
Thank you, nice presentation
@lusanivhangani27684 ай бұрын
Glad you liked it! Thank you.
@AlexD-ng2pn6 ай бұрын
If pepsin denatures proteins, what happens with glucose oxidase and catalase in a stomach? Do they denature?
@lusanivhangani27686 ай бұрын
Thank you for engaging with my content. To answer you, what will catalase and GO be doing in the stomach? that is a different environment than what they are used to. Hypothetically speaking, the high acidic pH would render those enzymes inactive by altering the native confirmation.
@AlexD-ng2pn6 ай бұрын
Great explanation. Thank you Dr.Vhangani. Could you explain how antioxidants play their role in lipid oxidation process?
@lusanivhangani27686 ай бұрын
Good day Alex, Thank you for engaging with my content. In terms of your question, I usually use the Farmer's hydroperoxide mechanism to explain how antioxidant function to inhibit/prevent oxidation. Lets start at initiation - metal initiators that abstract the hydrogen can be chelated using antioxidants such as EDTA, prolonging the induction period. In the propagation stage, oxygen scavengers can react with oxygen . Free radical scavengers can donate hydrogen to alkyl, peroxyl or alkoxy radicals, to prevent them from stealing another Hydrogen from a new fatty acids
@mostafamohamed34857 ай бұрын
Thanks a lot for valuable course
@mostafamohamed34857 ай бұрын
Very helpful and excellent explain thank you
@mostafamohamed34857 ай бұрын
Thank you very much
@ukaszdebiec95648 ай бұрын
Oh i was also wondering that if oxidation and degradation of fats need Oxygen to happen, than vaccum-packaging of products like meats or someything and also keeping oils in glass bottles that are 100% full (no much oxygen inside) should stop this reaction and preserve this products. Or are there some other possibility to degradate fats without oxygen ?
@lusanivhangani27687 ай бұрын
Thank you for engaging with my content. Regarding your question, the oxygen appears in the second step of the induction stage. Therefore in this case, without it oxidation will not proceed under the conditions of vacuum and maybe Modified and Controlled Atmospheric Packaging that you alluded to. But lets not forget in cases where the enzyme lipoxidase (lipoxygenase) is present and active in the product, it catalyses the reaction of an unsaturated fatty acid to directly form lipidhydroperoxides without the aid of oxygen. The formed peroxides will then further break down to continue the reaction provided the are initiators such as metals or higher temperature. So to answer your question directly, yes lipids can become rancid without the oxygen only if the enzyme lipoxidase is present.
@ukaszdebiec95648 ай бұрын
Thank you for your very nice video! I have one question - I heared once from food-production profesor that people can't smell oxidation of vegetable oils as they can do with animal fats. I'm wondering what he meant, from what i understand it might be, but you told that primary oxidation products can't be perceived. So maybe vegetable oils secondary oxidation products are mostly some products that also cant be detected easily by human and animals turn into something else like more alcohol less polymers or something like that? Or maybe its not about fats but other things that are in that products like amins because they are not "clear". Can you confirm / explain shortly that ? Thanks! BTW. My own experience from kitchen confirms that for example sunflower oil which is more unstaturated and hence unstable can stay for 1-2 years and you dont see that it changed, while egg fish or butter or anything else you can easily see and smell when its not fresh.
@lusanivhangani27687 ай бұрын
Thank you for engaging with my content and for the question. In my own experience, I have come across a vegetable oil (sunflower) that oxidised, and produced an off flavour. However, this oil I had extracted (crude) myself ,and left at room temperature for 3 - 5 years. This experiment was for educational purpose for my students. The oil became rancid and started forming gums around the opening of the bottle (PET). I have never experienced any rancidity of animal fat, in the period of normal use. It would be interesting to get hold of the literature or research the Professor was using, it might be that that is another lipid phenomenon. But I surely stand by the notion of saturated fats are less prone to oxidation than their unsaturated counterparts'. In terms of your observations, just note that commercially sorls sunflower oil is refined first, and then added with the antioxidant TBHQ. Moreover, you probably had it stored under proper conditions. Fish on the other hand oxidises much quicker. Butter undergoes hydrolysis easily than oxidation, and whatever off-flavours you perceived were related to hydrolytic rancidity. There is another type of oxidation "photooxidation" that is seldom talked about, and it affects a lot of dairy products during display in retail shops. In the case of products that contain other food components other than just lipids, they would also accelerate oxidation due to presence of these other components. Lipid degradation is such a complex phenomenon. I hope I shed some light, but i have different experience and opinion from the Professor
@LilP658811 ай бұрын
helped me study for an exam. Thx a lot.
@lusanivhangani276811 ай бұрын
You are welcome
@jaydeepmore1479 Жыл бұрын
Plz explain thermal decomposition of fat also
@lusanivhangani27687 ай бұрын
Thank you for engaging with my content. I would like to believe that the content in the video " Chemical changes of fats and oils during frying" does describe the process of thermal degradation of lipids, focusing on points such as, elevated temperatures, presence of oxygen, fatty acid type. Thermal degradation of lipids is somewhat similar to normal oxidation but with its rate accelerated. For instance, at room temperature, oxidation might results in rancidity only, but thermal decomposition might results in rancidity, colour darkening and resin (gummy) like texture due to polymerisation. All that was covered in the video. I hope I answered your question.
@SelamWorku-ro7jm Жыл бұрын
❤
@secretstone82792 жыл бұрын
Hi, thanks for the great video! I really enjoy it! I would like to ask about the measurement of secondary oxidation products. Commonly, we are using the P-ANV test to measure it. We were thaught that the P-ANV will be in increasing trend over a period of storage time, however, when we measuring the P-ANV in the oils samples, we found out that there were times where we observed the month 3 samples has lower P-ANV value than month 1 samples. Just wondering how could this happened? What is the best explanation on this phenomenon? Thanks!
@lusanivhangani2768 Жыл бұрын
Thank you for taking your time to watch my videos, and giving feedback. Just a few questions: what type of oils did you work with? Were your storage conditions real time or accelerated? Reason being at high temperatures oils oxidise faster and form aldehydes and ketones which are then measured using P-anisidine value. However, continued storage under those conditions may lead to the next step of polymerisation of oxidation products (aldehydes and ketones) leading to increased viscosity (gummy/sticky). It might happen that the newly formed polymers do not represent the structure of an aldehyde or ketone, thus not being absorbed at 350 nm. Remember polymerisation is also a process, therefore, AV can reduce before the visual effects are perceived.
@lazybones20702 жыл бұрын
Thank you for this video. It helped me a lot😘. Keep uploading the good work 👍
@lusanivhangani27682 жыл бұрын
I'm glad the video was of help. Thanks.
@realchristopher43342 жыл бұрын
Goodness me! I do not understand how the heck I can understand this! I am not even a chemist! The best explanation of a highly complicated or sophisticated concept! Visual aid helps me a lot but this visual aid is very clear and very detailed!
@lusanivhangani27682 жыл бұрын
Hello Real Christopher. I am glad you found the content of this video simple to understand. Thank you for the positive comment, it gave me a boost to do more🤗.
@realchristopher43342 жыл бұрын
@@lusanivhangani2768 Ah ha! Makes sense now! I connected the dots! You are a scientist of Cape Peninsula University of Technology! Not some "tuition teacher" online. Many of those "teachers" complicate what is already complicated. Some of them oversimplify things to the extent that data becomes inaccurate or outright wrong. Simplify things but not any simpler.
@hakimbourouba61552 жыл бұрын
Thank uuuu 🌺
@DevastotraPoddar2 жыл бұрын
Very Nice explanation 👌 Short & Crisp..
@lusanivhangani27682 жыл бұрын
Thank you.
@ivyvera36072 жыл бұрын
Thank you so much for this video!! It was really helpful!
@lusanivhangani27682 жыл бұрын
I'm glad it was helpful. Thanks for watching.
@harrikurniawan26602 жыл бұрын
Hi, Sorry i have a question I curious about seasoning (adding salt) to potato or nuts before frying process Is it affect to the reaction during frying process?
@lusanivhangani27682 жыл бұрын
Hi There. Some authors have reported on the prooxidant effect of salt of meat and meat products, where salt was responsible for liberating iron from ions from Iron-containing molecules. Iron is known as an accelerator of the Lipid Oxidation induction period. In potatoes and nuts the salt can play a similar role if Fe and Cu are present, thus have the same effect. I haven't come across such in literature, I'm speculating. For more reading check: dx.doi.org/10.1016/j.foodres.2017.02.003
@harrikurniawan26602 жыл бұрын
@@lusanivhangani2768 hii, thankyou for the explanation.
@yallugly3632 жыл бұрын
Hello! Can I ask what will happen to the lipid’s properties if there was a simple chemical composition?
@lusanivhangani27682 жыл бұрын
Hi There. I'm assuming when you say "simple chemical composition" you referring to if the fatty acids were all saturated and maybe short chains. The same chemical reaction (lipid oxidation) will take place, the difference will be the onset of the reaction will be delayed for saturated fatty acids since it is takes more energy to abstract that hydrogen form saturated carbons. in some cases extreme conditions such as frying the oil/fat at high temperature repeatedly will accelerate the reaction. I hope this makes sense
@yallugly3632 жыл бұрын
@@lusanivhangani2768 Thanks you very much❤️
@yallugly3632 жыл бұрын
Oh wait, i meant to say simple chemical change not chemical compositin
@lusanivhangani27682 жыл бұрын
@@yallugly363 I'm glad i could be of help to you.
@lusanivhangani27682 жыл бұрын
@@yallugly363 Remember the extent of the chemical change depends on the extent on the factors, for instance the more the double bonds, the higher the temperature, the more the initiators such as sunlight and metals, the heightened the oxidation. Same applies when the fat/oil is stored at lower temperatures away rom direct sunlight, the lesser the change.
@ivonnyaanga30932 жыл бұрын
An understandable reason # amazing
@lusanivhangani27682 жыл бұрын
Thank you
@alipongariverab.unknown79222 жыл бұрын
very useful lessons to understand better the enzymatic browning reaction and its importance and applications in the food industry. I am grateful I came across this video, I learn so much and I can make use of this in my class.
@lusanivhangani27682 жыл бұрын
Thank you. I'm glad my content could be of help to you. All the best with your class.
@willildfn92892 жыл бұрын
Brilliant
@lusanivhangani27682 жыл бұрын
Thank you
@pacarkucustom78023 жыл бұрын
I'm sorry , i'm not clearly hear when you say before 'why when frying the oil become darker' . Is it male electricion?
@lusanivhangani27683 жыл бұрын
Hello there. The darkening is due to the "Maillard Reaction" due to sugar protein condensation.
@irisforgiarinipasini17533 жыл бұрын
Amazing explanation. Thank you very much, you have no idea how you are helping me. Happy I found you here. Thank you
@lusanivhangani27683 жыл бұрын
You are welcome. Thank you for viewing
@manoulaboub63803 жыл бұрын
Thank you very much, It's very helpful 🥺❤
@lusanivhangani27683 жыл бұрын
You are welcome
@shashikaalahakoon32873 жыл бұрын
Most sought video. Thanks
@lusanivhangani27683 жыл бұрын
Thank you
@shashikaalahakoon32873 жыл бұрын
@@lusanivhangani2768 Could you recommend something like Ascorbic Acid for balancing Banana Leaves?
@lusanivhangani27683 жыл бұрын
@@shashikaalahakoon3287 I'm not sure what you mean by balancing banana leaves. can you explain this concept.
@shashikaalahakoon32873 жыл бұрын
@@lusanivhangani2768 I need to freeze banana leaves for future use. So I thought of putting them in boiled water mix with Ascorbic acid. After 1 minute, I'll put them on Ice water before freezing. Do you think will it work?
@lusanivhangani27683 жыл бұрын
@@shashikaalahakoon3287 I have no knowledge of freezing banana leaves, sorry I cannot help in this regard.
@MySelf-kz3md3 жыл бұрын
I like those stupid examples 😄. In fact those examples helps me to understand the concept. 😉 Thank you Ma'am 🤗
@lusanivhangani27683 жыл бұрын
Thank you too. I will keep "the stupid examples"
@shaylynnevictoriamckop29423 жыл бұрын
Thank you so much. Such a clear explanation.
@lusanivhangani27683 жыл бұрын
Thank you for the feedback
@nommoiyu32583 жыл бұрын
Thank you for describing soo briefly. I have some questions Do lipid oxidation occur on esters of Fatty acid like tri, di, monoglycerides or on free fatty acid or on both ? And what's the relation between acid value and peroxide value of fat, is there a mathmetical relation ? Thank you ..
@lusanivhangani27683 жыл бұрын
Good day. Apologies for a late reply. Notification for this comment passed me. Yes, lipid oxidation will take place in any lipid (fatty acid) whether esterified or free. The acid value measures the fatty acids that broke/separated from the ester bond to form what we call (free fatty acids), the main reaction is on the ester bond, on the other hand, peroxide value is based on oxidation that took place on the actual hydrocarbon where ROOH was formed on the chain. These two are in directly related, since if a free fatty acid is formed, it's affinity is on the interface of the oil and air, thereby resulting in reduced surface tension, allowing oxygen to enter the oil and then cause oxidation, which will form ROOH (peroxides). The only mathematical relation I can say (based on my opinion) will be calculating the rate of peroxide formation between a pure lipid vs a lipid that has been hydrolysed to form free fatty acid.
@deomanglal-lan19583 жыл бұрын
This is a very good presentation. I would like to ask what book can you recommended where the free fatty acids reduce oxidative stability explained clearly as you discuss here in the presentation. (Time 20:22)
@lusanivhangani27683 жыл бұрын
Good day. Thank you for the compliment. I obtained this information form a review article by Choe, E. & Min, B.D. (2006). Mechanisms and factors for edible oil oxidation. Comprehensive Reviews in Food Science and Food Safety, 5, 169-186. I hope this information helps.