Studies of the quality parameters of blended oils and sensory evaluation of gram flour products

Mouni Sur,Vineel Si Megvth,Asif Shreef Mohmm,Srith Penyl,Mhuri Kulkrni,Anith Sreeypurey,Shnthi Kuthi

a Department of Food Technology,Jawaharlal Nehru Technological University,Anantapur 515002,India

b R&D Division,Sri Yuva Biotech Pvt Ltd,Hyderabad 500007,India

c Department of Biotechnology,Mahatma Gandhi University,Nalgonda 508001,India

d Department of Biotechnology,Sri Krishnadevaraya University,Anantapur 515002,India

e Department of Microbiology,Osmania University,Hyderabad 500007,India

ABSTRACT Blended oils have many uses when compared with single oils,due to presence of high Omega9 levels.They help in brain development and reduce the risk of heart diseases.This investigation of blended oils was chosen taking into consideration the regular use of coconut oil(CO),palm oil(PAO),peanut oil(PO),and groundnut oil(GO),and using these blends three popular South Indian snacks were prepared.The oil blending was in the proportion of 50:50 using four different oils.This study includes the physicochemical properties of blended oils such as their pH,colour,nutritional assessment,and changes in the parameters of mixed oils.Additionally,these oil mixes were utilized for preparing different types of gram flour snacksincluding potato fries,pakoda,and karasev.The shelf life of the snacks was studied,considering the changes in their synthetic and tangible attributes.The changes seen in the oil separated from the fried items were very close to that of the control.Tangible assessment of the prepared fritters showed that they were synthetically safe to eat for up to two weeks.Six oil blends(CO:PO,CO:PAO,CO:GO,PO:GO,PO:PAO,and GO:PAO)were prepared successfully.Among the blended oils,coconut oil with peanut oil showed the highest spread ability,while groundnut oil with palm oil showed the lowest spread ability.The coconut and groundnut oil blend showed the highest ratio(58.8%)of unsaturated to saturated fatty acids.Polyunsaturated linoleic acid(18:2;24.3%),α-linoleic acid(18:2;5%),oleic acid (18:1; 25%), capric acid (2.8%), lauric acid (1.8%), myristic acid (1.6%), palmitic acid(16:0;14.5%),and steric acid(18:0;9.2%)were seen in the coconut and groundnut oil blend.The palm and peanut oil blend showed the least ratio(51.4%)for unsaturated and saturated oils,with oleic acid(21%),lauric acid(1.9%),and α-linoleic acid(2%).Among all the blended oils,coconut oil mixed with groundnut oil showed the highest level of acceptability for gram flour products.The content of freefatty acids was veryhigh inthe combination of palm and peanut oil.The three gram flour products prepared using blends of coconut oil and groundnut oil showed good appearance(8%),flavour of the product prepared with combinations of groundnut(refined)oil has high acceptability,good texture(8%),high acceptability(8%)in taste and overall acceptability of sensory evaluation.These blends in the future may develop good quality oils giving a high shelf life to food products.

Keywords: Edible oils Blending Free fatty acid Shelf life study Sensory characteristics Peroxide value

1.Introduction

Dietary fats and oils are important substances that play a key role in maintaining good health.In the Indian culinary culture, use of edible oils plays an integral role in cooking for human consumption.Groundnut oil is used in most of the southern states, while mustard oil is commonly used in the northern states.Palm oil is the largest consumed vegetable oil in India, but mostly for commercial purposes like manufacturing of Vanaspati[1].Cooking oils can be categorized into three groups:(a) cheese, ghee, coconut oil, and palm kernel oils are the major sources of saturated fatty acids [2]; (b) linseed,soybean, corn, and sunflower oils are rich in linoleic acid and linolenic acids (PUFA); and (3) canola, mustard, rice bran, olive, and groundnut oils are rich in oleic acid(MUFA).Consumption of a diet that is rich in PUFA and MUFA decreases low-density cholesterol levels and increases high-density lipoprotein cholesterol, leading to risk of coronary heart diseases[3].According to the report of the National Institute of Nutrition,it is recommended to use a combination of oils in order to achieve all fatty acids,as single edible oils do not meet the criteria required for a healthy diet[4].Also,while cooking,the high temperature of the oil causes oxidative degradation, which also affects the shelf life of the cooked food [5].Food spoilage and shelf life depends on the oxidative degradation of vegetable oils [6,7].Blending of two or more oils with different physicochemical properties is the simplest procedure to make food products with a high shelf life along with less oxidative degradation.According to the Food Safety and Standards Authority of India, a single blend of a mixture of two edible oils is permitted in India[8].Blending of different oils not only improves the nutritional value but also increases the level of lipids and antioxidants as well as the quality of the oils [9,10].Sugano and Tsuji [11] have shown that the blending of rice bran oil (20%-30%) with safflower oil reduced the levels of plasma cholesterol and magnified the hypocholesterolemic effect,when compared with individual oils.In healthy and hyperlipidimic individuals, the blends of rice bran oil lowered the blood cholesterol concentration and the anti-hyperlipidemic effect[12-16].Different cooking methods and temperatures cause deterioration of the oils due to oxidative stress.Similar works of blended oils were reported with different edible oils like groundnut,soya bean,palm oil,olive etc.and their blended oils with physic-chemical studies along with sensory evaluation of products were reported [17-20].In order to reduce oxidative damage of unsaturated fatty acids, this study focuses on the preparation and physicochemical studies of blended edible oils such as coconut,palm, peanut, and groundnut (refined) in equal proportions.In this study we used two types of groundnut oils,raw and refined oils because of lot of difference in the presence of saturated and unsaturated fatty acids.Using these blends, three products were prepared using gram flour and the shelf life of these products was studied.Gas chromatography(GC)was used to study the fatty acid profile of the blended oils.

2.Materials and methods

Edible oils were purchased and collected in bulk from the Oil Millers Association of Hyderabad,India.Coconut,peanut, palm, and groundnut (refined) oils were selected as the control and as test oils to make blends.

2.1.Blending of edible oils

Coconut, peanut, palm, and groundnut (refined) oils were each mixed in the ratio of 50:50, and mixed in a blender for 1 h thoroughly,to form uniform blends.Evaluation of the blended oils was done using thermal stability and storage ability tests[21-24].

2.2.Physicochemical parameters of blended oils

Colour,spread ability of the oils,free unsaturated fats(FFA),peroxide value(PV),iodine value(IV),saponification value (SV) using the standard procedures of FSSAI manual (2016), colour using Hunter lab colorimeter(ColorFlex EZ Benchtop Spectrophotometer) [25], free fatty acids[26],and oil retention capacity[27]were analyzed.Free fatty acid studies were also identified using GC-MS(GCMSQP2010,SHIMADZU).

2.3.Preparation of food products using gram flour

2.3.1.Ingredients

The ingredients used for the products were gram flour 1,000 g,ghee 100 g,salt to taste,one teaspoon of chilli powder and half a litre of blended oil to fry each product.

2.3.2.Method of preparation of pakoda, potato fries and karasev

Pakoda:Ingredients mentioned were purchased from the local vendor(Hyderabad),mixed with appropriate quantity of water and moderately thin sliced onions.

Potato fries:Potato sliced into small sticks was dipped in the batter prepared by the ingredients mentioned and fried in the blended oils.

Karasev:Ingredients were made into thin paste like batter and karasev was prepared by mashing the batter into heated blended oils.

The prepared products were boiled to deep fry in the selected blended oils.Fat frying of these snacks was done in each oil mix at high temperature of(180 ±5)°C.Indistinguishable tests were additionally done with the control oils.The fried snacks were cooled to room temperature and packed in polythene bags.These bags were kept for 60 d and were opened occasionally(0,30,and 60 d)for sensory evaluation to study biochemical properties,correlation of oil quality, and taste of the products prepared in various mixes of oils[28].

2.4.Product analysis

2.4.1.Oil content investigation

The oil content in the prepared snacks was measured by soxhlet extraction method by AOAC technique(1984),utilizing oil mixed in ether (solvent) (b.p.40-60 °C) and extracting for 6 h.Different oils weight was evaluated by an electronic balance (M/s Sartorious Inc., Bangalore,India).

2.4.2.Storage

The prepared snacks were wrapped in a transparent cover and bundled in LDPE sacks.Nitrogen was inserted into them before fixing and then they were stored at-18°C for 10,20 30,and 40 d.The samples were marked for further study and were stored for organoleptic properties(taste,sight,smell,and touch)and sensory studies.

2.4.3.Sensory assessment

The samples kept in polythene packs were assessed by a panel of ten members as judges for their appearance,flavour,texture,taste,and overall acceptability during intervals of 0,30,and 60 d using a five-point hedonic scale.A calendar was created for assessment of the appearance,texture,flavour,taste,and overall acceptability of the product.Keeping in mind the objective of the study and to avoid predisposition,the items were undisclosed with regard to the kind of oil blend that was used,and were instead allocated codes.

2.4.4.Chemical study of the products

The prepared snacks were kept for a total of 60 d and the oil was removed using soxhlet at regular intervals of 0,30,and 60 d.The separated oils from the snacks were studied for different parameters like rancidity,acid value,peroxide value,free unsaturated fats,and para anisidine value using the standard protocols.These data were analyzed by mean and standard deviation[29].

2.4.5.Texture analysis of the products

The surface texture of snacks was studied by Instron Texture Analyzer (M/s Instron Inc., Buckinghamshire, UK,model number 4301).The browned wedges were cracked longitudinally with wedge molded test(60°cutting point,7 cm width)at a crosshead speed of 20 mm/min.The pinnacle acquired for each situation revealed the hardness of the singed wedge.The lower shear values showed a gentler item, while higher shear values indicated a harder item.The surface investigation parameters of the fried snacks were communicated as hardness (N).The trials were directed in triplicates and the qualities were accounted for as mean±SD[30].

2.4.6.Proximate analysis of the products

The lipid, fiber, protein, and fat levels of the products were analyzed based on the AOAC technique(1984).For reducing and non-reducing sugar estimation, dried potato sample was grounded to powder by mortar and pestle.The sugar was removed from the powder with water for 10 min at 60°C and it was utilized to dissect sugar content by Lane and Eynon technique[31].

2.5.Shelf-life study of the products

The prepared products were cooled at room temperature and then stored in the refrigerator at 5-10°C and collected for shelf life studies.They were made into fine powder and studied for the microbial count and organoleptic evaluation[32].

2.5.1.Observations recorded

The products were analyzed at regular intervals in a day for the accompanying parameters and recorded.

2.5.2.Organoleptic assessment of the items

They were analyzed for a month by a panel of 10 judges.The parameters considered were appearance,texture,flavour,taste,and overall acceptability.

2.5.3.Development of score card

A five-point scale was used for the quality check:5-excellent, 4-good, 3-fair, 2-poor, and 1-very poor.A score card was created to assess the suitability of the items.The investigation was conducted in a room which was free from all aggravations during mid-evening.

2.5.4.Microbiological assessment of the items

Microbiological tests were conducted in the first and third months for every product.Total plate count (TPC),yeast,coliform,and E.coli presence were studied by standard protocols[33,34].

2.6.Statistical analysis

The data were analyzed statistically using ANOVA and CRD two-factor completely randomized design.Means were measured using triplicates and the least significant difference (LSD) test at P = 0.05 was studied.Statistix 8.1 was used for the purpose of statistical analyses in the study [35].

3.Results and discussion

The four selected oils,coconut,peanut,groundnut,and palm oils were taken as the base oils and blended in equal proportions.Coconut oil is colourless and soft in nature,palm oil is dark yellow and little hard in nature.Peanut oil and groundnut oil (refined) are dark and light yellow in colour respectively and hard in nature.The proportions used were arrived at as they had shown better quality attributes when the food products were fried using these oils.Basing on this,the following oil blends were prepared:coconut oil-peanut oil (CO + PO), coconut oil-palm oil(CO+PAO),coconut oil and groundnut oil(CO +GO),peanut oil-groundnut oil(PO+GO),peanut oil-palm oil(PO+PAO),groundnut oil-palm oil(GO+PAO).

Variations of different proportions like 50:50, 60:70,70:30,and 80:20 were tested to check the suitability to fry the products.After a number of trials,the 50:50 proportions were chosen as the standard proportion,as it was at an acceptable level with regard to the viscosity of the oils.In addition, the ratio of 50:50 is advisable for blended oils,because oils showed less toxic compounds after heating when compared to other proportions.

3.1.Quality characteristics of blended oils

3.1.1.Physical characteristics

3.1.1.1.Colour.The colour of the blended oils was different from the individual oils, showing a slight variance(Table 1).When coconut oil was blended with peanut oil and palm oil,it showed a pale yellow colour,while coconut oil with groundnut oil,groundnut oil with peanut oil and palm oil, and peanut oil with palm oil showed a yellow colour.

3.1.1.2.Spreadability.The spreadability of the blended oils is given in Table 2.While coconut oil with peanut oil showed the highest spreadability,groundnut oil with palm oil showed the lowest spreadability.

Table 1 Colour observed in each selected blended oil sample before and after heating.

The main purpose of testing the spreadability of oils is to know the viscosity of different oils.Spreadability as a test is also used in baking and gel formation of oils for commercial use.It is mainly used for the post-baking spreading in industries.Spreadability is tested using the line spread test.Because of their thickness the spreadability time is greater for these oils.In this study,the spreadability for palm oil when mixed with other oils is very poor[25].In some studies,the viscosity and heat transfer coefficients for canola,corn,palm,and soybean oils are high and concluded that the frying time and oil temperature significantly affected the viscosity.The study found that corn oil had the greatest increase in viscosity over a period of 36 h[26].

3.1.2.Chemical characteristics

The chemical parameters of the blended oils are very important to assess the quality of the combination of oils and the shelf life of food products.The results of the study showed that the free fatty acid values was very high(0.8 mg) in the combination of palm and peanut oils,while low free fatty acid values were observed in coconut and palm oils(0.3 mg KOH/g oil).It reflects the freshness and deterioration of the materials and also the quantity of glycerol to be released as a result of neutralization of oils.High acidity oils or fats produce excess smoke during heating(Fig.1).Free fatty acid values reflect the freshness and deterioration of the materials and not the quantity of glycerol to be released as a result of neutralization of oils[27].

3.1.3.Peroxide value for different combinations of oils

According to the graph in Fig.1,the saturated fat in palm oil showed high rancidity.When palm oil was mixed with peanut,coconut,and groundnut oils,these combinations showed high peak points (0.7 meq (Milliequivalents per liter)) in peroxide estimation.This is, however, lesser in combinations of peanut oil blends with groundnut oil and coconut oil,at only 0.4 meq(Fig.1).The palm oil contains high oleic acid and has greater stability against oxidative deterioration than the normal seed oil.Hence, lesser increase in the free fatty acid and peroxide value is observed in palm oil[28].

Table 2 Spreadability of the blended oils.

Fig.1.Chemical parameters of blended oils.

3.1.4.Iodine number for combination of oils

Coconut and groundnut oils are good cooking oils because of their dryness.When coconut oil is mixed with groundnut oil, it leads to a high iodine number at 0.6 mg/g.By contrast, when peanut oil is mixed with palm oil,there is low iodine number at 0.3 mg/g[29].

3.1.5.Saponification number for oil combinations

According to Fig.1,the blend of coconut oil and groundnut oil has a saponification number of 0.32 mg KOH/g oil.However,soybean oil blends with coconut and peanut oils showed a low range of saponification at 0.16 mg KOH/g oil(Fig.1).

These chemical parameters suggest that the oils used to develop blends are acceptable due to high free fatty acid values.The results showed acceptability of chemical parameters of groundnut and coconut oil blends when compared to the other blended oils.

3.2.Gas chromatography and mass spectrometry

The blended oils were studied using gas chromatography and mass spectrum (GC-MS) after change in their relating methyl esters.Among the blended oils, the coconut and groundnut oil blend showed the highest ratio of unsaturated to saturated fatty acids (58.8%).Capric, lauric, myristic, palmitic, and steric acids were present in all the blends used in this study.Polyunsaturated linoleic acid (18:2) 24.3%, α-linoleic acid (18:2)5%, oleic acid (18:1) 25%, and capric acid 2.8%, lauric acid 1.8%, myristic acid 1.6%, palmitic acid (16:0)14.5% and steric acid (18:0) 9.2% were seen in the coconut and groundnut oil blend.Of all the blends, the palm oil and peanut oil blend showed the least ratio (51.4%)for unsaturated and saturated oils, as well as in oleic acid (21%), lauric acid (1.9%), and α-linoleic acid (2%)(Table 3) [34].

3.3.Cooking quality characteristics of blended oils

3.3.1.Temperature

The temperature of heated oil was recorded in seconds.The two combinations of coconut oil with palm oil and groundnut oil showed high temperatures at 165 °C.The smoking point for the groundnut oil mix with peanut oil is very low.

Table 3 Fatty acid composition of different oil blends.%

3.3.2.Cooking time

The time taken for the food products prepared with the combinations of palm oil with peanut oil and groundnut oil is very less.The cooking time is 30 and 35 s,respectively.This is the fastest cooking oil combination.The moderate cooking temperature at 35 and 40 s is seen in the combinations of coconut oil with groundnut oil and peanut oil,respectively.

3.3.3.Products developed using selected blended oils

Using the selected blended oil combination of coconut and groundnut oils,we have prepared pakoda,potato fries and karasev.These products were further studied for their shelf life(Figs.2-4).

3.4.Sensory evaluation comparison of blended oil products

According to the rating given by consumers,the product prepared with coconut and groundnut oil (refined) had good appearance(8%),while palm oil mixed with peanut oil(6%),showed a moderate appearance.There was a significant difference of 5%[34].

Colour is said to be the main aspect that directly impacts the acceptability of any food.Foods fried with coconut oil and peanut oil blend showed the best appearance at 7.5%.It showed a significant variance of 1%.Other mixed oils showed moderate colour acceptance[35].The colour differences between raw and heated blended oils were studied.All the blended oils except coconut and groundnut oil blend,changed the colour even at different composition ratios(Table 1).

Fig.3.Sensory evaluation of products made up of blended oils.

Fig.4.Overall acceptability of the product for blended oils.

Flavour increases the acceptability of food.Fig.3 showed that the flavour of the product prepared with combinations of groundnut oil(refined)had high acceptability.The product prepared with coconut oil gave average flavour acceptability.The product prepared with coconut oil mixed with peanut and groundnut oils(7%)showed a similar variance[36].

Fig.2.Appearance of the products fried in blended oil.

The soft, hard, and crisp texture of the products has a great impact on the consumption rate.Texture does not give any significant variance with the blended oils.The coconut and groundnut oil combination showed good texture(8%).All the combinations of coconut oil and groundnut oil showed an almost similar texture of the products[37].

As seen in Fig.3,coconut and groundnut oils gave high acceptability (8%) in taste, while peanut oil mixed with palm oil gave a low rate of acceptability(6%).All the combinations of coconut oil and groundnut oil gave a relatively high score and were found to be within the acceptable limits of preference[38].

3.5.Overall acceptability

The overall acceptability showed the combination of oil most acceptable for consumption.Among all the blended oils, coconut oil when mixed with groundnut oil showed the highest level of acceptability.When compared with all the combinations of oils,only coconut oil combined with palm and peanut oils gave a consumer acceptable range of the blended oil product.The acceptability of the product attains the maximum score if it attains good colour, flavour, texture, and overall taste (Fig.3)[39,40].

According to the data in Fig.4, when blended oils are compared with each other in their appearance, texture,taste,colour,flavour and overall acceptability,a 5%significant difference between appearance and a 1%significant difference (P ＜0.01) in colour are observed.Texture,taste,flavour,and overall acceptability did not show any significant difference.The cooking quality of all the blended oils clearly demonstrated good acceptance scores of all the five sensory characteristics,and thus good overall acceptability.This experimental research is interesting and helpful to promote the blending of different oils for better well-being instead of adhering to the common usage of single oils.Texture and flavour show the significant difference should be 5%(P ＞0.05).The combination of coconut and groundnut oils gave good texture and appearance because of their dry nature[41].

4.Conclusion

Blending of oils is the solution to reduce the oxidative damage,maximize fatty acids,and increase storage stability.This work was conducted to investigate the quality parameters of blended oils by preparation of fried Indian snacks using gram flour.The oils selected for the study were coconut,peanut,palm,and groundnut oils,and the selected blends are CO + PO, CO + PAO, CO + GO,PO+GO,PO+PAO and GO+PAO.The proportions selected for the blended oils were at 50:50,because of their higher acceptability.From the results,it can be concluded that the snacks fried in the coconut and groundnut oils blend gained the maximum acceptability among all the other variations.Among those having high linoleic acid oils, coconut oil was considered the best along with its blends,and gave beneficial results with minimum increases in the peroxide,free fatty acid,iodine,and saponification values.The coconut and groundnut oil blend showed the highest ratio (58.8%) of unsaturated to saturated fatty acids.Capric acid,lauric acid,myristic acid,palmitic acid and steric acid were present in all the blends used in this study.Polyunsaturated linoleic acid (18:2) 24.3%, 5%α-linoleic acid (18:2), oleic acid (18:1) 25% and 2.8%capric acid, 1.8% lauric acid, 1.6% myristic acid, 14.5%palmitic acid(16:0)and 9.2%steric acid(18:0)were seen in the coconut and groundnut oil blend.The palm and peanut oil blend showed the least ratio(51.4%)for unsaturated and saturated oils,and also in oleic acid(21%),lauric acid(1.9%),and α-linoleic acid(2%).The preparation of these blends in the future may develop good quality oils giving a high shelf life to food products.

Conflicts of interest

All the authors confidently declare that there is no conflict of interest, and paper is approved by all authors for publication.

Acknowledgement

The authors wish to express his special thanks to management of Sri Yuva Biotech Pvt.Ltd., Hyderabad, and Telangana,India.