|Title of Invention||
"A METHOD FOR RANCIDITY EVALUATION OF DEEP FRIED SNACKS."
|Abstract||A rancidity shelf life evaluation kit is invented which is capable of assessing the oxidative status and shelf life of deep fat fried products such as khara sev, khara boondi, potato chips and salted ground nuts on the shelf in the market place away from the laboratory. So far such a kit is not available to the market/consumer. This kit comprises of two solutions namely A&B, liquid C and solid crystals D. The solutions and liquid are provided in 10ml ampules and solid crystals in a pouch which is meant for one time use. The reagent can be prepared at the out door market place by mixing solutions A&B and crystals D together in a beaker E provided with the kit. The product to be assessed for shelf life and oxidative status of the inherent fat is dipped in beaker E with the reagent, removed after soaking, air dried on a watch glass G and again dipped in liquid C in the beaker F. Development of blue color instantaneously on the surface of the product indicates the shelf life between 2 and 8 weeks and also oxidative status of the fat. Blue color indicates that oxy-compounds have formed in sufficient amount to effect the organoleptic quality of the product. The results indicated by the kit has been successfully corroborated by physico-chemical, spectral and sensory values such as moisture %, oil % peroxide value, absorbance at 232, 230 and 265nm and organoleptic acceptability obtained for the product which were analyzed after every 15 days for a period of 8 weeks.|
|Full Text||The present invention relates to a method for rancidity evaluation of deep fried snacks.
Fried snacks / products, mostly starch based are very favorite item in the Indian food habits. However the bulk of the fried snacks coming to our market are from cottage industries, where much of the quality control does not apply, for the reason as these products are sold unbranded, lose and move very fast. However care is taken in the organised sector to use fresh/relatively good quality oil for all deep frying purposes. But after the product is prepared, packed and sent to the market, appreciable amount of time is lost before it reaches to the consumer. Realizing the severity of the problem some of the industries have started packing their products under nitrogen atmosphere which invariably escalates the cost of the product and forces the consumer to go for cheaper, unbranded, items which do not display history of the product. Methods are available based on primary and secondary oxidation products for detection of oxidation in oils and fats. We also have well laid out procedure for assessment of oxidative stability and self-life of oils/fats as such. But there is no clearcut protocol developed so far to evaluate shelf life of deep fried snacks/products away from the laboratory, within minuets. This kit can be used by industries to monitor their products at the market place and also by consumer. The kit is simple, reliable and uses three solutions and a chemical. It requires very small quantity (~2 gms) of the product to be evaluated.
Reference may be made to Islas -Rubio AR, Vasquez-Lava F., Islas-Valenzuela CI, Mercado-Ruiz JN, and Grandos. Nevarez M.C. Development of rancidity in com chips and fried com tortillas with various storage treatment: Center de Investigation en Alimentactiony Desarrollo, A.C. Apdo, Postal 1735, Carretera a la Victoria KM 0.6,
Hermosillo, Sonora, Mexico, CIAD/DTA or RC/99/001. Where in a study was conducted to explore the suitability of gas chromatography, couped with solid phase microextraction (SPME) for measuring the development of rancidity in com chips and fried com tortillas "tostados" has been carried out. Five batches of samples were packed in poly propylene bags and stored at ambient temperature up to 20 weeks, than analyzed for peroxide value, free fatty acids, precent fat, precent moisture and hexanal content. Samples were evaluated by an untrained panel to correlate the sensory attributes to rancidity and hexanal value detected by GC-SPME. The PV, FFA, and hexanal concentration varied with type of snack, storage time and quality of the frying oil. PV ranged from 0.44 to 17% whereas FFA values were between 0.03 and 5.3%. Fat content flactuated between 17 to 35%. In general, com chips developed rancidity sooner than tostadas. Sensorial evaluation showed higher rancidity scores with storage time and overall acceptability was higher for tostados. Hexanal was not detected in samples fried with fresh oil and stored for 1 week. However com chips stored for 4 weeks showed a hexanal concentration equivalent to that of tostados stored for 20 weeks. The maximum hexanal concentration was 135ppm. Although this technique is employed for similar purpose but is different than reported in this specification in the sense that it uses gas chromatography coupled with solid phase microextraction for estimation of Hexanal to predict the shelf life of the product.
References may be made to Li CT,Wick M and Marriott N.G. Evaluation of Lipid oxidation in animal fat, the Ohio State University Department of animal sciences. Special circular 172, (1999). Where in a modified peroxide value (MPV) method was compared to the 2-thiobarbutric acid (TBA) test as method of analyzing the lipid
oxidation in subcutaneous lamb fat obtained from lambs fed with 15 lU and 300 lU α-tocopherol. This method is not directly related as it is carried out on extracted fat and not on the product as a whole.
References may be made to Harris N.E., Westcott DE and Henick AS.,. Rancidity in almonds-shelf life studies, J. Food Sci, 37:824-827, 1972 where in rancidity in almonds was studied by storing diced unroasted and roasted nuts for periods upto 6 months at o degree F and 100 degree F. Both glazed and unglazed samples were stored in hermetically sealed cans in air packs and assayed by chemical and sensory methods. Data showed that diced unroasted almonds remained acceptable to consumer panel for 6 months at 100 degree F. On the other hand diced roasted almonds became unacceptable to panel after 3 months at 100 degree F. Changes in free fatty acids, iodine value and moisture content were found to be not useful indicators of rancidity. However, oxygen content of the headspace gas of almonds stored in cans at 100 degree F, as measured by GLC, agreed well with sensory data. This method depends on gas-chromatography analysis of head space oxy-compounds mainly aldehydes and ketones, which is a well laid procedure of sensory analysis. However it is not related with the protocol and basic element of the kit presented in this invention.
The main object of the present invention is to provide a kit for rancidity evaluation of deep fried snacks which obviates the draw backs as detailed above.
Another object of the present invention is to develop a reagent which can be used to evaluate rancidity of fried products.
still another object of the present invention is to evolve a solvent system which can penetrate inside the product and bring the deteriorated fat on the surface of the product for further reaction.
Yet another object of the present invention is to derive a correlation between the oxidative/shelf life status of the fried product and the sensory acceptability in relation concentration of reagent when constituted together.
Accordingly the present invention provides a nnethod for rancidity evaluation of deep fried snacks which comprising preparing the reagent by way of mixing solutions A and B such as herein described, and subsequently adding crystal D such as herein described, in a glass beaker E (50ml capacity) for generating a straw color solution, liquid C such as herein described, is taken in a second glass beaker (50ml capacity) and dipping a small portion (1-5 gm) of fried product selected from group consisting of sev, khara boondi, potato chips, fried salted groundnuts, noodles or any other starch based low moisture fried product in the said reagent beaker E for one minute, taking out the product, air drying for one minute on a watch glass G and dipping in the said liquid C in second beaker F wherein the development of blue color instantaneously on the surface of the product indicates the product is being rancid and shelf life is between two and eight weeks.
The present invention provides a process for the preparation of a kit for rancidity evaluation of deep fried snacks comprises of solution A containing ethyl alcohol and methyl alcohol, solution B containing de-ionized water and solid crystals D of potassium halide, where solution A,B and liquid C are provided in 10 ml ampules separately while solid D (20-lOOmg) is provided in a pouch for one time use, which can be utilized for preparing the reagent by way of mixing solutions A and B and subsequently adding crystal D in a glass beaker E (50ml capacity) generating a straw colour solution, liquid C is taken in a second glass beaker (50ml capacity) as it is, when a small portion (l-5gm) of fried product like khara sev, khara boondi, potato chips, fired salted groundnut, noodles or any other starch based low moisture fried product is dipped in the reagent beaker E for one
minute, taken out, air dried for one minute on a watch glass G and dipped in liquid C in second beaker F, development of blue colour instantaneously on the surface of the product indicates the product is rancid and shelf life is between two and eight weeks, which is directly related to the deterioration of fat in the product.
In an embodiment of the present invention shelf life of various fried products like khara sev, khara boondi, potato chips, fried groundnuts laddo and chakali which are prepared by deep fat frying, packed in poly propylene bags and stored for a period of eight weeks simulating market conditions have been subjected for evaluation of rancidity, vis-a vis deterioration/oxidation of fat using the kit.
In another embodiment of the present invention a reagent has been prepared using solution A and B, and solid D which helps the polymerized/deteriorated fat selectively to come up on the surface of the product and form a colour complex.
The kit comprises of three glass ampules containing solutions A and B and liquid C and a pouch containing crystals D. The ampules contain 10ml of solution each. The first step to use the kit is to prepare a reagent. The ampules containing solution A and B are opened up and mixed together in a glass beaker E provided along with the kit. To this mixed solution the total amount of crystals D present in the pouch is added after cutting open the pouch. The solids are slowly dissolved in the solution by swirling as crystals are sparingly soluble in the medium. A glass rod may be used if necessary for agetation. After the crystals are completely dissolved it gives a straw colour reagent ready to be used. The second step comprises of opening the ampule containing liquid C and draining it into another glass beaker F provided with the kit. A pinch (l-2gms) of deep fat fried product to be evaluated for its rancidity/ shelf life is removed from the shelf/package and
dipped in the reagent beaker E for 1 min. There after it is remove from the reagent and kept on a watch glass G for one min to air dry. After the product is air dried it is dipped in the beaker F. The development of blue colour complex on the surface of the product as superficial coating indicates that product is rancid and the shelf life of product is more than two weeks depending on the type of product.
Fats and oils present in fried foods undergo changes during storage, which results in the production of unpleasant taste, odor, and toxic artifacts. These changes are due to autoxidation of inherent fat present in fried foods such as potato chips, fried legumes, cookies, laddus etc. The decomposition products and rate of their formation vary with the nature of fat used, the surface volume ratio, the excess of air and interval of heating. As on today no reagent is available which can determine the status of the oil present in the food, without extracting the fat out of the product. Hence, it was envisaged to develop a kit comprising of a reagent which can evaluate the oxidative status of the product indicating their shelf life. Oxidation is considered to be the most common of the causes of fat deterioration. For the determination of degree of oxidation, peroxide value, carbonyl value, TBA value and free fatty acids are normally determined. It is very well known that primary oxidation products are peroxides and hydroperoxides and secondary oxidation products are aldehydes, ketones and acids. Among these oxidation products peroxides and hydroperoxides are normally not present in food in the native form, where as aldehydes, ketones and acids are some times part of food ingredient present naturally. Hence, peroxides were aimed to be detected using a reagent/or kit for fried products direct from the shelf
When fat is oxidized, hydroperoxides are formed as a primary oxidation product. They are broken, some times, to hydroperoxides. Peroxides and hydroperoxides generated in native oils are determined volumetrically using potassium iodide and titrating against sodium -thiosulphate solution using starch as indicator. However such method can't be adopted for products as such, there fore a search was conducted to select a medium which can take out the fat, specially the deteriorated fat out of the product in such a way that it does not travel in the solution. Utilizing ethyl alcohol, methyl alcohol, propyl alcohol in the presence of ethers such as 2- methoxy ethanol, 2- ethoxy ethanol, ethylene glycol mono ethyl ether in combination made it possible to drag deteriorated fat (oxidized fat) out of the product but remain embedded at the surface of the product. As the above solvents and chemicals are liquid and polar in nature, they get associated with the peroxides and hydro peroxides, developed due to autoxidation in the product and when the product was taken out from the solution beaker E and kept on watch glass G to air dry, tend to come out due to capillary action and remain at the surface for a while. When this air dried product is dipped into beaker F containing liquid C which is de-ionised water, the potassium halide present in the product along with the reagent, liberates the halogen gas due to action of peroxides, hydro peroxides and ethers, which in turn react with starch present as one of the food ingredients and develops a blue colour complex. This blue colour complex can not form unless halogen is in the atomic form which can come only through halides. Halides especially potassium halides are very stable salts and in normal course do not dissociate and allow the halogen to leave in the gaseous form even in aqueous medium, where they are highly soluble. Therefore reduction of potassium halide to liberate halogen requires a highly potential reducing
agent like peroxides and hydro peroxides which are coming through fat oxidation. The
mechanism of action is given in scheme -1
Scheme -1. MECHANISM OF ACTION FOR GENERATION OF BLUE COLOR.
The following example are given by way of illustration and there fore should not be construed to limit the scope of the present invention.
The solvents normally used for fat extraction are hexane, petroleum ether, chloroform: methanol 2:lv/v. The products with low moisture and high fat such as potato chips, khara sev, noodles and laddos (20gm each) were taken in a glass beaker separately and dipped in the above solvents (75ml each). Product remaind in the solvent for 1 hour and later taken out. To get the fat for check up, solvents had to be removed by heating, which can not be done at home or at market place. Due to this draw back these set of solvent discarded.
Another set of solvents such as benzene, methyl alcohol, ethyl alcohol, butyl alcohol, dichloromethane, acetonitrile, acetone, 2. Methoxy ethanol, 2-ethoxy ethanol, and isopropanol have also been made use to extract fat for this purpose. The products such as khara sev, chakali, noodles and laddos (l0gm each) were soaked in these solvents (50ml each) separately at room temperature for 1 hour. Afterwards the solvents were decanted out and used for starch iodine test. One percent starch solution and saturated solution of potassium iodide (2ml each) was added to solvent extract (10ml) separately in a test-tube and shaken vigorously. No blue color noticed in other solvent extracts except in 2-ethoxy ethanol, 2 methoxy ethanol and acetonitrile.
Hundred and two milliliters of solvent mixture namely methyl alcohol 2ml, ethyl alcohol 50ml, 2-ethoxy ethanol 50ml, was prepared and added crystals of potassium halide to make a saturated solution in extraction solvent. Ten milliliters of above saturated solution was taken in a 100ml capacity beaker for experiments. The products like noodles, khara sev, potato chips and laddos which have low moisture and high fat have been taken for experiments. A pinch of these products were dipped into above solution in the beaker for 10 min and later removed and kept out to observe any change on the products. There was no change on the surface of the products.
Fifty milliliter each of ethyl alcohol and 2-ethoxy ethanol and 2ml each of methyl alcohol and 2-methoxy ethanol was mixed together to make a uniphase solution. To this 600mg of potassium halide was mixed and dissolved completely to make a reagent. Ten milliliters of this solution was taken in a 100ml glass beaker and 2gm each of the products such as khara sev, khara boondi, potato chips (one product at a time) was dipped in the beaker containing reagent for 1 min and made sure that product has completely taken up the reagent. Subsequently the product is taken out from the reagent and air dried for a while and dipped into another 100ml beaker containing 20ml of deionised water. The development of blue colour on the surface of the product showed that
inheren't fat was deteriorated and product is old/stale. However fresh product didn't show any color.
Estimation of evaluation efficacy of kit with respect to shelf life of the fried products
Four products namely khara sev, khara boondi, potato chips and salted groundnuts have been prepared following the traditional recipies where postman brand refined groundnut oil was used for deep fat frying to obtained deep fried products for experiments and evaluation of shelf life. All these four products were subjected for evaluation of shelf life at 0 residence time using the kit and following the procedure described earlier, but none of them developed blue color on the surface of the product indicating product was fresh and oil used was good. Four set of (50 gms each) khara sev, khara boondi, potato chips and salted groundnut samples have been packed in polypropylene pouches in duplicate and thermatically sealed, to study the shelf life of products making use of the kit at 15 days interval for a period of 60 days. The samples were stored simulating the market conditions on the shelf as it is kept in a shop. One set of samples was used for chemical analysis to arrive on the right concentration of the reagent and another set was used for sensory analysis to check the overall quality. The amount of solvent mixture was kept constant at 104 ml however, the amount of halide has been changes between 600 to l00mg for the purpose of compatiability of sensory score, organoleptic taste and fat deterioration data. Results are given in table-1.
Table 1. PHYSICO-CHEMICAL, SPECTRAL AND SENSORY DATA ON FRIED PRODUCTS USED FOR SHELF LIFE-EVALUATIONDEEP
Oil rancidity and shelf life of khara sev, khara boondi, potato chips and salted ground nuts were evaluated employing the rancidity evaluation kit and data has been correlated with physico-chemical, spectral and sensory acceptability values. Oil content of all the four products varied between 37.1 and 63.3% minimum in salted ground nuts and maximum in khara boondi because of their hard and hollow nature respectively. However, moisture % ranged between 0.7 and 5.3. There was not much effect of storage time on these parameters as expected. However peroxide value, which is highly crucial in terms of rancidity/storage/ shelf life studies has varied between 10.3 to 89.2,12.8 to 64.5,10.8 to 122.4 and 1.3 tol02.0 for khara sev, khara boondi, potato chips and salted groundnuts respectively. The peroxide value has linearly increased in all the cases but decreased after 30 days and again increased as expected. Peroxide value do decrease as soon as secondary oxidation product start forming and again increases involving fresh olefinic molecules. Although peroxide value is a very good indicator of autoxidation but do not have taste and odor of its own. But once secondary oxidation products start forming, there is always an off odor in the product. UV- visible Spectral Analysis of Products Stored for Different Period
Samples namely khara sev, khara boondi potato chips, and salted groundnuts which were stored for a period of 0,15,30,45, and 60 days separately to assess their acceptability with respect to sensory attributes and also to check the efficacy of rancidty evaluation kit have been taken for UV-visible spectral analysis. The oil extracted from the products are taken for spectral recording. The oil extracted from the above products (50mg) were taken in graduated tubes separately and diluted to 15 ml with spectroscopic grade hexane. One milliliter of this stock solution was made up to
15ml with hexane and this diluted solution was used for UV- visible spectral analysis. Absorbance recorded at 232nm corresponds to Cis,trans conjugate double bonds where as absorbance at 230 and 265 were indicative of conjugated mono ene-one system present in the oil generated due to heat and oxidation. However absorbance recorded at 200nm is normal and for cis- double bond naturally present in the glyceride molecules. Spectral data present in Table -1 showed that although deterioration started after 15 days of storage but it was highly prominent after 45 and 60 days of storage, which was also corraborated by use of kit and development of blue colour. Sensory evaluation of stored deep fat fried snacks
Deep fat fried snacks as mentioned above were packed in poly propylene pouches and stored under ambient conditions (23-30°C and 25-75% RH). Samples were drawn at interval of 15 days. Quality of stored products was tested by conducting sensory evaluation with special reference to detection of rancidity. The results showed that the samples were in good condition (without sensorily detectable rancidity) or organo leptically acceptable for the duration of storage as given in Table -2
TABLE-2.DAYS OF STORAGE OF PRODUCT FOUND FIT FOR CONSUMPTION
Sample Days of storage
1. Khara boondi 15 days
2. Potato chips 30 days
3. Khara sev 45 days
4. Salted ground nuts >60 days
Khara boondi had the lowest storability, where as salted groundnuts had more than 60 days of shelf life.
These samples were further tested using the kit after every 15 days interval of time and found agreeing with sensory and physico-chemical-spectral data. The khara boondi was found to develop blue colour after just 15 days of storage where as potato chips, khara sev and salted groundnuts developed blue color on the surface only after 30,45 and 60 days of storage respectively. Other words they were organoleptically acceptable for 15,30,45 and 60 days respectively. Hence, it can be concluded that kit with a pre-determined concentration of reagent was agreeing with the laboratory data can be taken as an authentic tool to assess the self life of fried products at market place.
Example-6 Shelf life evaluation of unpacked products
The same set of samples i.e. Khara sev, khara boondi, potato chips and salted groundnuts have also been stored along side without packing (lose) at ambient temperature (23-30°C) to check the shelf life. These products were found organoleptically acceptable till 15 days of storage, but rancidity started just after 7 days as evidenced by Kris color test. Use of kit showed appearance of blue color after 20days when slightly bitter taste was also developed in all four samples.
The main advantage of the present invention are: 1. A kit provided to the industry and consumer to evaluate rancidity and the shelf life of
fried products and determine whether the snack is good or bad for consumption
before it is sold or purchased.Ingredients of the reagent are provided separately in the kit which is for one time use. Reagent can be prepared at the time of use and later discarded. Hence, there is no problem of expiry of reagent.
2. Product can be evaluated fairly accurately away from the laboratory without use of any form of energy
3. The kit along with the shelf life also gives information regarding the oxidative status of the oil present in the product.
4. It can be used as a quality surveillance tool for the organised sector or by the cottage industry/consumers in remote places as well.
1. A method for rancidity evaluation of deep fried snacks which comprising preparing the reagent by way of mixing solutions A and B such as herein described, and subsequently adding crystal D such as herein described, in a glass beaker E (50ml capacity) for generating a straw color solution, liquid C such as herein described, is taken in a second glass beaker (50ml capacity) and dipping a small portion (1-5 gm) of fried product selected from group consisting of sev, khara boondi, potato chips, fried salted groundnuts, noodles or any other starch based low moisture fried product in the said reagent beaker E for one minute, taking out the product, air drying for one minute on a watch glass G and dipping in the said liquid C in second beaker F wherein the development of blue color instantaneously on the surface of the product indicates the product is being rancid and shelf life is between two and eight weeks.
2. A method as claimed in claim 1 wherein solution A containing ethyl alcohol and methyl alcohol, solution B containing ethylene glycol mono ethyl ether and 2-methoxy ethanol, liquid C containing de-ionized water, solid crystal D is solid potassium halide.
3. A method for rancidity evaluation of deep fried snacks substantially as herein described with references to the example.
|Indian Patent Application Number||218/DEL/2002|
|PG Journal Number||31/2009|
|Date of Filing||14-Mar-2002|
|Name of Patentee||COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH|
|Applicant Address||RAFI MARG, NEW DELHI-110001, INDIA|
|PCT International Classification Number||G01N 33/02|
|PCT International Application Number||N/A|
|PCT International Filing date|