Physicochemical properties, rheology, and storage stability of salad creams made from different cassava starch varieties

Received: 28 February 2020 | Revised: 15 May 2020 | Accepted: 29 May 2020 DOI: 10.1111/jfpp.14662 ORIGINAL ARTICLE Physicochemical properties, rheology, and storage stability of salad creams made from different cassava starch varieties D. M. Adeleke1,2 C. O. Eromosele5 | T. A. Shittu1 | A. B. Abass3 | W. Awoyale4 | S. O. Awonorin1 | 1 Department of Food Science and Technology, Federal University of Agriculture, Abeokuta, Nigeria 2 Department of Biotechnology, Faculty of Applied and Computer Sciences, Vaal University of Technology, Vanderbijlpark, South Africa 3 International Institute of Tropical Agriculture, Eastern African Hub, Dar es Salaam, Tanzania 4 Department of Food, Agriculture and Bioengineering, Kwara State University, Ilorin, Nigeria 5 Department of Chemistry, Federal University of Agriculture, Abeokuta, Nigeria Abstract The use of cassava starch as potential substitute for corn starch in the production of salad cream (SC) may contribute to sustainable utilization of cassava roots. This study investigated the physicochemical properties, rheology, and storage stability of SC made with starches from eight cassava varieties. SC produced was stored in an airtight plastic jar for 3 months at ambient temperature (25 ± 2°C). Changes in the physicochemical properties, rheology, and storage stability of the stored SC samples were determined using standard methods. There was a significant decrease (p < .05) in the solid contents of the SC while the peroxide increased with storage period. There was a significant increase (p < .05) in the total plate count (TPC) of the SC samples with storage period. This study further showed that the SC samples were all Correspondence D. M. Adeleke, Department of Biotechnology, Faculty of Applied and Computer Science, Vaal University of Technology, Private Bag X021, Vanderbijlpark 1911, Andries Potgieter Blvd, South Africa. Email: doyinsolaadeleke@gmail.com chemically and microbially stable considering the standards for peroxide value (PV) Funding information German Federal Ministry for Education and Research (BMBF); Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH cally feasible, it is practically imperative to find a locally available replacement for corn (<10 meg/kg) and TPC (<10 4 cfu/g) within the 3 months storage. Practical applications The salad cream (SC) consumed in Nigeria is mainly imported and expensive. Local brands of the product are scarce in the grocery. SC is produced majorly from modified corn flour or starch with other ingredients. To make local manufacture of SC economistarch. This study was then conceived to screen starches from some elite cassava varieties for use in SC production. It has been established from this study that the cassava starches tested could be a suitable substitute for corn starch for the production of SC. However, the most stable SC from textural point of view was derived from a yellow fleshed cassava variety (TMS 1206), which is very important for the consumer preference. With appropriate addition of other ingredients in the production, consumers are assured of best quality SC. 1 | I NTRO D U C TI O N food and nonfood sectors of industry (Ayetigbo, Latif, Abass, & Müller, 2018). Cassava starch is used to produce variety of val- Starch is one of the major derivatives of fresh cassava roots. It ac- ue-added products such as sweeteners, alcohol, acids, and other counts for 30%–35% of fresh cassava roots (Oghenejoboh, 2012). chemicals (Sriroth, Piyachomkwan, Santisopasri, & Oates, 2001). Cassava starch is a highly suitable material for food and indus- Cassava starch is used in industries due to its high yield, very trial use. It is edible, nontoxic, and functionally important in the low cost, and unique characteristics such as a clear viscous J Food Process Preserv. 2020;00:e14662. https://doi.org/10.1111/jfpp.14662 wileyonlinelibrary.com/journal/jfpp © 2020 Wiley Periodicals LLC. | 1 of 11 2 of 11 | ADELEKE Et AL. paste (Sriroth et al., 2001). These unique characteristics of cas- salt, vinegar, vegetable oil, and egg were purchased from a super- sava starch make it advantageous for use in food applications market (Shoprite, Ibadan, Nigeria) and an open market (Kuto market, such as tapioca grits (Eke, Achinewhu, & Sanni, 2010), and salad Abeokuta, Nigeria). cream (SC) (Ashaye, Sanni, & Arowosafe, 2010; Eke-Ejiofor & Owuno, 2014). Salad cream belongs to a class of foods commonly referred 2.1 | Cassava starch extraction to as salad dressing. According to Food and Drug Administration (FDA), salad dressing is defined as a semisolid emulsified food The method described by Oyewole and Obieze (1995) was used with the same ingredient and optional ingredients as mayonnaise for cassava starch extraction. Fifty kilogram of roots from the with the exception of cooked starch paste (Karas, Skvarãa, & eight cassava varieties each were peeled, washed in water, and Îlender, 2002). There are two types of salad dressing, namely, grated with a locally fabricated mechanical grater. The resultant pour-able and spoon-able dressing which vary in flavor, chemi- pulp was sieved immediately through a muslin cloth suspended in cal, and physical properties (especially viscosity). The example of about 70 L of water. This process separated the fibrous and coarse spoon-able salad dressing is mayonnaise and the pour-able one root materials from the starch pulp. The starch pulp was allowed to is SC (Babajide & Olatunde, 2010). SC is an emulsified creamy settle for 7–8 hr before decanting the supernatant. The sediment yellow viscous sauce made from mixture of water, vegetable oil, (starch) dried in a locally fabricated convective oven at 60°C for vinegar, and maize starch as major ingredients (Eke-Ejiofor & 18 hr, packed in a polyethylene bag, stored in a covered container, Owuno, 2014). It is popularly consumed with salad, which is a and kept in a cold storage for further use. The dried starch was popular ready-to-eat dish often containing raw or cooked vege- milled and sieved through 106 μm mesh size before further use in tables usually served chilled or at a moderate temperature. The the study. inclusion of SC in vegetable salad improves the taste of the vegetables thus more vegetables could be consumed for more health benefits, asides the nutritional benefits of the cream. Starch 2.2 | SC preparation serves as a stabilizer, gelling, binding, thickening, and emulsifying agent in commercial salad dressings (Schlesinger & John, 1996). The ingredients used in the SC preparation were water, sunflower The possibility of using cassava starch in SC preparation was oil, vinegar, dry cassava starch, salt, sugar, egg yolk, and mustard recently reported by Adebayo, Otunla, and Ajao (2009) using powder. The proportion by weight of these ingredients in the for- different cassava starch varieties, Ashaye et al. (2010) using mulation was 44.23, 24.91, 14.89, 7.57, 4.42, 1.77, 1.23, and 0.98%, cassava starch and Eke-Ejiofor and Owuno (2014) using cassava respectively. The procedure of SC preparation was similar to that de- and sweet potato starches. The authors concluded that cassava scribed by Babajide and Olatunde (2010) with some modifications. starch based SCs compared favorably with commercial salad in Dry cassava starch was first reconstituted with water after which chemical composition, functional properties, viscosity and sen- vinegar, salt, sugar, and mustard powder were added. The mixture sory attributes. Our previous study (Akinwale et al., 2016), which was then cooked until it was translucent. This was then cooled at corroborated the applicability of cassava starch as potential refrigeration temperature and blended in a warring blender for maize substitute in SC production further indicated that SC from 1 min after which egg yolk and vegetable oil were added, and then, yellow fleshed roots were more preferred to that from white blended for 5 min. The resultant SC was then poured into a covered fleshed roots. There is, however, paucity of information on the plastic jar. storage stability of SCs from cassava starches. Information on the storage stability of cassava starch based SC could reinforce the drive toward commercial application of cassava starch as 2.3 | Chemical analysis substitute for corn in SC making. The objectives of this study were to determine changes in the physicochemical properties and rheology of ambient stored SC from The proximate composition of the starch samples were determined using AOAC methods of analysis (AOAC, 2010). different cassava starches, and also to determine the storage stability of cassava starch based SC from different varieties. 2.4 | Determination of pH 2 | M ATE R I A L S A N D M E TH O DS This was determined using a digital pH meter (Model HI 2210, Hanna Instrument Inc., USA). Standardization of the pH meter was carried Eight fresh cassava varieties (TMS 01/1368, TMS 01/1412, TMS out using buffer solutions of pH 7 and 4. About 1.5 g of starch sam- 01/1206, TMS 01/1371, 30572, TMS 419, TMS 96/1632, TMS ple was dissolved in beaker with 10 ml of distilled water and stirred 98/0581) were harvested from the International Institute of Tropical properly. The pH meter was inserted into the solution and the read- Agriculture, Research Farm, Mokwa, Niger State. Mustard, sugar, ing taken. | ADELEKE Et AL. 2.5 | Determination of sugar and starch 3 of 11 was then heated for 3 hr in an air oven at 100°C, and then, cooled in a desiccator and weighed quickly. The % Residue was reported as The starch and sugar content were determined using the method of total solid. (Dubois, Gillies, Hamilton, Rebers, & Smith, 1956; Eke et al., 2010). About 0.2 g of the sample was weighed into a centrifuge tube with 1 ml of 100% ethanol, 2 ml of distilled water, and 10 ml of hot ethanol. %Total solids = W2 − W1 × 100. S The mixture was vortexed and centrifuged for 10 min at 2,000 rpm using Sorvall centrifuge (Newtown, Connecticut, USA), model GLC-1. The supernatant was decanted into another centrifuge tube; 2.8 | Determination of titratable acidity (TTA as % lactic acid) this was used for sugar determination and the sediment was used for starch determination. For sugar determination, 9 ml of distilled Twenty grams of sample were weighed into a warring blender and water was added to the supernatant and was vortexed. An aliquot of mixed for 15 s at low speed and for 1 min at high speed. The mixture 0.2 ml was then pipetted into a test tube and 0.8 ml of distilled water, was filtered and made up to volume with 200 ml of distilled water 0.5 ml of phenol, and 2.5 ml of concentrated H2SO 4 were added and and this was titrated against 0.01 M of NaOH. vortexed. The sample was allowed to cool and the absorbance was read on a spectrophotometer, model spectronic 601, Milton Roy Company, USA, at 490 nm wavelength. %Sugar = Absorbance − Intercept × Dilution factor × Volume Weight of sample × Slope × 10,000 %TTA(as lactic acid) = 9 × N2 × V2 × V0 V1 × P where N2 = Normality or molarity of NaOH, V2 = Titer Volume, V1 = Volume of extract used, V0 = Total Volume of extract (which is 200 ml), P = Weight of sample taken. For starch determination, 7.5 ml of perchloric acid was added to the sediment and allowed to stand for 1 hr; then, 17.5 ml of distilled water was added to it and vortexed. An aliquot of 0.05 ml of 2.9 | Determination of peroxide value the solution was pipetted into a test tube; 0.95 ml of distilled water, 0.5 ml of phenol, and 2.5 ml of H2SO4 were added and vortexed. The Peroxide value (PV) was determined as described by (AOCS, 1989; mixture was allowed to cool and absorbance was read on a spectro- Tolve, Condelli, Can, & Tchuenbou-Magaia, 2018). A mixture of gla- photometer (Model 601 Milton Roy Company, USA), already stan- cial acetic acid and chloroform in the ratio 3:2 v/v, respectively, was dardized at 490 nm wavelength. prepared and 20 cm3 of it were pipetted out and added to 1 g of each of the samples weighed into a 250 ml of conical flask. 0.5 ml of Absorbance−Intercept × Dilution factor × Volume × 0.9 %Starch = Weight of sample × Slope × 10,000 potassium iodide solution was added to the mixture and the solution obtained was titrated with 0.01 M of Na2SO3 until the orange color almost disappeared, and then, 0.5 ml of starch indicator was added, 2.6 | Determination of color the titration continued until the blue color disappeared. The flask content was shaken vigorously near the end point to ensure that all This was determined using color meter (CR-410, Japan). The colorim- the iodide was liberated from chloroform layer. The preparation of eter operates on the CIE (Commission Internationale de I’Eclairage) blank was performed in a similar way. L*, a*, b* color scheme. Multiple measurements of several points on samples were made. After calibrating the instrument by counting a Peroxide value = ( ) M Va × Vb zero calibration mask followed by white calibration plate, about 3 g of W starch were put in a transparent polythene bag and the color meter was placed on the sample by allowing the sensor to touch the sample. M = Molarity of NaSO3, W = Weight of the sample, Va = Volume of The reading was taken directly for L*. The instrument displays three- the sample, Vb = Volume of the Na2SO3 (test titer). dimensional color difference in uniform color space (Lab) coordinates. Uniform color space defines three directions, a Light to Dark direction, called L*, a Red to Green direction called a*, and a blue to yellow direc- 2.10 | Rheological properties tion called b* (Petterson, McWatters, Hung, Chinnan, & Phillips, 2002). The viscosity of different cassava starch based SC samples were measured in triplicates using a Digital Rotational Brookfield 2.7 | Determination of total solids Viscometer, Model DV-E, Brookfield Engineering Laboratories Middleboro, USA). Three readings were taken per sample at 20, 30, About 3 g of sample were weighed into a flat petri-dish heat on 40, and 60 min rotation at each speed (30, 60, and 100 rpm). Spindle steam bath for 15 min, exposing maximum bottom to live steam. It No 5 was used for all measurements. A 600 ml beaker was used for 4 of 11 | ADELEKE Et AL. 3 | R E S U LT S A N D D I S CU S S I O N all measurement with the viscometer guard leg on. The samples were poured into the beaker to reach a level that covered the immersion 3.1 | Proximate composition of SC from cassava starches groove on the spindle shaft. All viscosity measurements were carried out immediately after preparing the SC. The proximate composition of the fresh SC samples from the dif- 2.11 | Storage studies of cassava starch based SC ferent cassava starches is shown in Table 1. The moisture content ranged from 55.46% to 65.07%, with TMS 01/1412 having The SC samples were poured in a covered plastic jar, labeled the highest, while TMS 01/1206 had the lowest. The moisture and stored under ambient temperature (25 ± 2°C) for 3 months. content observed in this study was higher than that reported by Chemical parameters such as protein, moisture content, ash, Ashaye et al. (2010) of the range 35.44 and 48.99% and also that starch, sugar, PV, color, fat, total solids (TS), total titratable acidity of Babajide and Olatunde (2010) who reported 48.80 and 49.79% (TTA), and rheological parameters were carried out on them at the for corn-cocoyam-based SC. However, the results obtained were end of 1, 2, and 3 months, respectively, as done for the fresh SC similar to that of Eke-Ejiofor and Owuno (2014) for SC from cassava samples. and potato starches. The slight variation in the moisture content of the SC samples might be due to genetic composition of the different cassava roots used in producing the SC. Protein content of the fresh 2.12 | Microbiological analysis SC samples ranged from 1.49% to 2.18%, with TMS 01/1368 having the highest value while sample 30,572 had the lowest. There was a One gram (1.0 g) of cassava starch based SC was homogenized in significant difference between the fat content of the fresh SC sam- 9.0 ml sterile 0.1% peptone water for 30 s (normal speed) to a ho- ples. Fat content of the fresh SC samples were also similar to the mogenous suspension, and then, a 10-fold serial dilution in peptone result obtained by Ashaye et al. (2010) on cassava starch (different water was carried out. varieties) based SC. It was reported that fat content in low calorie For total aerobic bacteria count, 1 ml of aliquot from suitable di- mayonnaise to be between 30% and 40% (Dudina et al., 1992). The lutions was plated on Nutrient agar (CM003, Oxoid Ltd, Basingstoke results of this study showed that the SC is of low calorie category Hants, England) plates, the plates were incubated at a temperature and it was lower than the amount (31%) reported by McCance and of 37°C for 24 hr. Total plate count (TPC) was enumerated and was Widdowson (1987). The ash contents ranged from 0.95% to 1.25%. expressed as number of colony forming units/g. TMS 01/1371 had a higher value and TMS 98/0581 had the lowest ash content. There was a significant difference (p < .05) in the ash contents of the cassava starches. The ash content of the SC sam- 2.13 | Data analysis ples were slightly lower than the results (1.04%–2.04%) reported by Prescott and Board (1993) for different mayonnaise samples. Analysis of Variance (ANOVA) was used to analyze data obtained This may be due to the presence of starch in the SC samples, which and significant effect of independent variables at 5% level was differentiates SC from mayonnaise as starch is not among the in- separated using Duncan's Multiple Range test. (SAS version 9.1). gredients for producing mayonnaise. The sugar content of the SC Linear regression of sample viscosity with storage time was done samples ranged from 5.01% to 6.21% with TMS 01/1412 having using Statistical Package for Social Sciences (SPSS version 21.0) the highest sugar content and the lowest was recorded by TME software. 419. The sugar contents of the SC samples showed a significant TA B L E 1 Proximate composition of fresh SC from cassava starches Sample (%) Moisture content TMS 01/1368 60.65 ± 0.01b 2.18 ± 0.00a 26.61 ± 0.01b 0.99 ± 0.02e 5.17 ± 0.01f 12.58 ± 0.03a TMS 01/1371 b 60.60 ± 0.01 2.03 ± 0.13 b d a c 11.82 ± 0.03f TMS 96/1632 65.03 ± 0.06a 1.53 ± 0.00 d 16.79 ± 0.01a 0.84.38 ± 0.01g 5.93 ± 0.01d 12.31 ± 0.01f TMS 01/1412 65.07 ± 0.12 a b e f a 11.92 ± 0.02e TMS 01/1206 55.46 ± 0.59d c Protein TMS 30572 60.01 ± 0.01 TMS 98/0581 65.00 ± 0.01a a TME 419 65.01 ± 0.01 Fat Ash 24.34 ± 0.02 Sugar 1.25 ± 0.02 Starch 6.01 ± 0.01 22.81 ± 0.01 0.96 ± 0.01 2.03 ± 0.13b 27.72 ± 0.01a 1.03 ± 0.02d 5.12 ± 0.02g 12.19 ± 0.01d d c c b 2.03 ± 0.06 6.21 ± 0.01 25.20 ± 0.01 1.10 ± 0.02 6.14 ± 0.01 12.43 ± 0.03b 1.75 ± 0.00 c 18.91 ± 0.01f 0.95 ± 0.00 f 5.56 ± 0.01e 11.41 ± 0.01g c b b h 10.75 ± 0.03h 1.49 ± 0.06 1.78 ± 0.06 26.62 ± 0.01 1.21 ± 0.01 Note: Mean values having different superscripts within the same column are significantly different (p < .05) 5.01 ± 0.01 | ADELEKE Et AL. 5 of 11 difference (p < .05). There was also a significant difference (p < .05) 01/1371(96.87) and the lowest value was recorded in TMS 96/1632 in the starch contents of the fresh SC samples. The values ranged (86.71). The lightness (L*) of the SC samples was significantly different from 10.75% to 12.58% with TMS 01/1368 having the highest value (p < .05). The yellowness (b*) values ranged between 15.56 and 21.54 while TME 419 had the lowest. with TMS 96/1632 having the highest value and TMS 98/0581 had the lowest. Redness (a*) ranged between −0.49 and −1.42 with TMS 01/1371 having the highest while TMS 01/1412 had the lowest. Color 3.2 | Chemical composition of fresh SC from cassava starches is one of the most important quality attributes of SC because it is a criterion a consumer uses to select SC brand from the market. The yellowish color of SC is primarily provided by egg yolk carotenoids (Ferial, Table 2 shows the chemical composition of fresh SC from cassava Abu-Salem, & Azza, 2008). The color results for lightness (L*) was starches. The pH of the SC ranged from 3.29 to 3.44 with TMS similar to the findings of Ashaye et al. (2010), SC from TMS 01/1371 01/1412 having the highest value and TMS 01/1206 had the low- showed a higher degree of lightness (L*) and this could be due to vari- est value. The pH values obtained in this study were similar to the etal differences because generally, cassava starch produces very clear values obtained by (Radford & Board, 1993). The pH of SC can sauces which are advantageous in many industrial processes (Oyewole have a dramatic effect on the structure of the emulsion (Radford & Obieze, 1995). & Board, 1993). The pH is an indication of keeping quality of the product. Total solid values ranged from 56.66% to 34.32% with TME 3.4 | Apparent viscosity of fresh SC from cassava starches 419 having the highest TS while TMS 01/1206 had the lowest. TMS 01/1368 had the highest titratable acidity and the lowest was recorded by sample 30,572. The PV ranged from 0.23 to 0.66 meq/ kg with TMS 01/1206 having the highest value while TMS 01/1368 Table 4 shows the apparent viscosity of freshly prepared cassava had the lowest. There was a significant difference between the PVs starches SC. Viscosity of the SC ranged between 2,538.67 and of the cassava starch based SC samples. PV is used to determine the 4,772.00 CP with TMS 01/1368 having the highest, while TMS content of reactive oxygen of fat and oil in terms of milli equivalent 01/1206 had the lowest at a speed 30 rpm. There was a significant of oxygen per kg that oxidize KI under condition of test. The oxida- difference (p < .05) in the viscosities of the SC samples. The high- tion of fats and oils is due to the formation of peroxides, aldehydes, est viscosity value was 4,772 centipoise and this was observed at and ketones (Gray & Roobinson, 1997). SC sample made from TMS the lowest shear rate (speed and time) exhibiting a thinning prop- 01/1206 was observed to give a higher PV among other SC samples. erty that is the viscosity decreased with increase in shear rate and This indicated higher oxidation of its fats and oils compared to other this implies a pseudoplastic behavior. All the SC samples viscosities SC samples even though the value is still much lower than the stand- exhibited a pseudo plastic behavior (Non Newtonian behavior) as ards for PV (<10 meg/kg) for SC. the shear rate increase the viscosity decreases, highest viscosity was observed at lowest shear rate exhibiting a thinning properties. (Morris, 1989). A non-Newtonian fluid is a fluid whose viscosity is 3.3 | Color parameters of SC from cassava starches variably based on applied stress, their flow properties are not described by a single constant value of viscosity (BahramParvar, Razavi, The result of the color parameters of the SC from cassava starches & Khodaparast, 2010; Rha, 1975). This implies that the viscosities of is presented in Table 3. Values of lightness (L*) was high in TMS the SC samples cannot be described by a single viscosity value. TA B L E 2 Chemical composition of fresh SC samples from cassava starches Total solids (%) Total titratable acidity (%) Peroxide value (meq/kg) 3.31 ± 0.06e 63.25 ± 0.02c 5.76 ± 0.24a 0.23 ± 0.02h a f e 0.28 ± 0.05g 4.67 ± 0.00 b 0.31 ± 0.01f 62.44 ± 0.02 4.28 ± 0.00 c 0.61 ± 0.01b 3.29 ± 0.06f 56.66 ± 0.06g 3.24 ± 0.00 e 0.66 ± 0.01a d d e 0.55 ± 0.06d Samples pH TMS 01/1368 TMS 01/1371 3.43 ± 0.00 TMS 96/1632 3.42 ± 0.01b TMS 01/1412 3.44 ± 0.01 a TMS 01/1206 60.67 ± 0.06 63.32 ± 0.00b e 62.96 ± 0.02 3.24 ± 0.00 TMS 30572 3.34 ± 0.01 TMS 98/0581 3.43 ± 0.01a 63.32 ± 0.01b 3.24 ± 0.00 e 0.43 ± 0.01e c a d 0.57 ± 0.06c TME 419 3.38 ± 0.06 64.32 ± 0.06 3.03 ± 0.18 4.04 ± 0.21 Note: Mean values having different superscripts within the same column are significantly different (p < .05) 6 of 11 | ADELEKE Et AL. 3.5 | Changes in proximate composition of SC from cassava starches during storage autooxidation of unsaturated and polyunsaturated fats and oils (Ogbonnaya & Yahaya, 2008). The ash content also showed a significant decrease at the end of the storage period. The sugar con- The proximate composition of the SC samples from cassava starches tent of TMS 01/1368, TMS 01/1371, and TMS 98/0581 was not during storage is shown in Table 5. The moisture content during stor- significantly different (p < .05) after 1 month of storage; but there age ranged from 50.96% to 65.07%. The moisture content showed was significant decrease at the end of the storage period. The starch no significant difference (p < .05) initially during the storage period content of the SC samples ranged from 11.14% to 13.50% and there but there was a slight decrease in the moisture content at the end was significant difference (p < .05) in their starch contents at the end of the storage period. There was a decrease in the protein content of the storage period. at the end of the storage period. Protein content of the samples decreased significantly (p < .05) as the storage time increased. The decrease would have been due to chemical changes that may have taken place during storage of the SC samples. This could lead to an 3.6 | Changes in chemical composition of SC from cassava starches during storage emulsion with low viscosity and lower stability as the protein content reduces (Ferial et al., 2008). Figure 1 shows the changes in pH, TS, titratable acidity, and PV of the The fat content of all SC samples significantly decreased at the SC samples during storage. There was a significant decrease (p < .05) end of the storage period. The fat content decreased at the end of in the pH content of the SC samples at the end of the storage period. storage probably due to the breakdown of fats and oils to give free After first and second month of storage, there was no significant fatty acids (Ogbonnaya & Yahaya, 2008). The decrease could also difference (p < .05) between the SC samples. The pH decrease in be attributed to lipolytic activities of enzymes, referred to as hy- SC and this could be due to increase in storage temperature, as the drolytic rancidity, and thereby allowing oxidative enzymes catalyze higher the rate of metabolism of sample (sugar), the higher the rate the oxidation of the oils by atmospheric oxygen and the degraded of acid production (Adebayo et al., 2009). At the end of the storage fatty acids radiation gives rise to volatile substance with objec- period, there was a significant difference (p < .05) in the TS of the tionable odor and flavor (Ogbonnaya & Yahaya, 2008). Similarly, SC samples as reflected by decrease in protein, starch, sugar, and to fat containing foods, SC is susceptible to spoilage through the fat contents of the SC samples. TTA of the SC samples increased at the end of the storage period probably due to the activity of hydro- TA B L E 3 Color parameters of SC from cassava starches lytic and oxidative enzymes that may be present in the eggs used (Stefano, 1989). According to Ferial et al. (2008), free fatty acids may Samples L* a* b* TMS 01/1368 88.46 ± 0.34cd −1.22 ± 0.01b 20.13 ± 0.04b TMS 01/1371 96.87 ± 1.21a −1.42 ± 0.01c 20.19 ± 0.32b TMS 96/1632 86.71 ± 1.29d −1.17 ± 0.03b 21.54 ± 0.35a cleavage in products and subsequently increase the acid value. This TMS 01/1412 88.53 ± 3.19b-d −0.49 ± 0.09a 19.71 ± 0.96b oxidation could have occurred with the aid of oxidative enzymes and TMS 01/1206 87.48 ± 0.23cd −1.23 ± 0.02b 18.62 ± 0.06c the presence of a proportion of atmospheric oxygen in the head- TMS 30572 90.05 ± 1.94bc −1.35 ± 0.03c 20.61 ± 1.20ab space incorporated into the SC. There was an increase in PV of all SC TMS 98/0581 91.28 ± 0.33b −1.23 ± 0.08b 15.56 ± 0.19d samples with increase in storage period. These findings were similar b b to the findings of oils (Ogbonnaya & Yahaya, 2008). According to TME 419 90.02 ± 0.25 bc −1.22 ± 0.01 20.07 ± 0.24 30 rpm TMS 01/1368 4,772.00 ± 365.20a 100 rpm 3,604.33 ± 795.17ab TMS 01/1371 4,557.00 ± 1,408.51 TMS 96/1632 3,306.67 ± 227.45b 2,480.00 ± 401.73d TMS 01/1412 3,422.20 ± 180.83 b d TMS 01/1206 2,538.67 ± 294.25b a TMS 30572 4,411.33 ± 254.25 TMS 98/0581 2,704.00 ± 410.01b TME 419 4,675.33 ± 129.06 a 4,543.00 ± 1,087.84 2,253.33 ± 197.38 molecular weight will develop through the accumulation of acidic showing the susceptibility to go rancid with time during storage. 60 rpm a acid esters. In advanced stages of oxidation, free fatty acids with low their findings, PVs of mayonnaise samples increased during storage Note: Mean values having different superscripts within the same column are significantly different (p < .05) Samples be produced by the oxidation of double bonds of unsaturated fatty 2,900.00 ± 504.77bc a 2,106.67 ± 462.19d 3,391.00 ± 424.47 bc 1971.33 ± 303.27d 3,722.33 ± 400.88 ab 4,323.00 ± 1,093.23a 1999.33 ± 221.63cd 2068.67 ± 41.49cd 1904.00 ± 361.75d 2,660.00 ± 469.28bcd 1752.00 ± 198.92d 3,008.00 ± 146.04b Note: Mean values having different superscripts within the same column are significantly different (p < .05) TA B L E 4 Apparent viscosity of SC made from cassava starches at different rotational speed | ADELEKE Et AL. TA B L E 5 Changes in proximate composition of SC from cassava starches during storage Time of storage (month) 1 2 3 Starch source (%) Moisture content Protein Ash TMS 01/1371 60.53 de TMS 96/1632 63.33b 1.49jk 24.11a 0.61a TMS 01/1412 64.99 a cd o 22.39 0.50 r TMS 01/1206 53.31i 25.66d 0.84i g TMS 30572 59.15 TMS 98/0581 63.33b b 2.11 c-e 1.92 1.96 1.89d-f kl 1.41 1.68i hi c Sugar 60.60 TMS 01/1368 a Fat d 25.82 24.03 24.92 k f jk 0.79 g 0.94 0.88 h 16.80 x 0.71m g 0.79 k 5.16 7 of 11 Starch r 13.04b i 11.78q 5.99 5.91mn b 6.18 5.08u 12.24j 11.84p 12.10 l e 12.38h 5.55p 11.30 v 6.11 12.70 c TME 419 63.31 1.71 TMS 01/1368 60.59d 1.96cd 24.79g 0.76l 5.14s 12.81c f-i l l k 11.62s ef TMS 01/1371 60.21 TMS 96/1632 60.00 f TMS 01/1412 64.80 a TMS 01/1206 51.06j 1.78 1.38kl 1.82 f-h 24.71 5.98 i 22.89 0.76 14.76b 0.53q 5.89k 12.18k t s c 11.71r 20.59 1.75g-i 20.74s m p 0.44 0.60 o 6.16 5.05v TMS 30572 58.92 1.27 22.22 TMS 98/0581 61.99c 1.53j 15.85y 0.65n 5.51q 11.24w TME 419 60.04f 1.49jk 22.18p 0.69m 5.97jk 12.64f de e-g j TMS 01/1368 60.52 1.85 TMS 01/1371 60.14f 1.68i TMS 96/1632 59.90 f TMS 01/1412 64.74a TMS 01/1206 50.96 j TMS 30572 58.82g 1.09n 21.89q c jk z 1.34 lm 1.75g-i 1.68 i 24.11 m 6.08 f 12.06m g 0.82 j 5.96 t 12.30 l 12.73de 0.71 5.12 22.60 n 0.74l 5.92lm c r 5.85 20.01v 0.40 t 7.09f u p v 5.04 12.01n 0.78k 6.05g 12.25j o q 14.00 20.23 0.51 0.58 o 11.51t 12.11l 1.61s 15.17 0.61 5.49 11.14x 1.42j-l 21.25r 0.69m 5.91mn 12.60 f 3.73 0.27 3.90 0.21 0.41 0.55 0.66 0.05 0.69 0.04 0.07 0.10 P of starch source (S) * * * * * * P of time of storage (T) * * * * * * P of S × T * Ns * * * * TMS 98/0581 61.81 1.46 TME 419 59.98f Std dev Std error Note: Mean values having different superscripts within the same column are significantly different (p < .05). *Interactions significant at p < .05. The PVs obtained in this study were less than 10 indicating that (p < .05) in lightness (L*) and yellowness (b*) in all the SC samples the SC samples were relatively stable to rancidity. Pearson (1990) at the end of the storage period. The primary source of yellow stated that a rancid taste begins to be noticeable when oil has a PV color in SC comes from the egg yolk. Therefore, the oxidation of of 10–20. The PVs were seen to increase gradually over the months the carotenoids might have caused the decrease in the yellowness indicating that SC goes rancid gradually on storage (Finberg, 1995). of the samples. 3.7 | Changes in color parameters of SC from cassava starches during storage 3.8 | Changes in apparent viscosity of SC from cassava starches during storage Figure 2 shows the parameters [Lightness (L*). Redness (a*) and Figure 3 shows the viscosity of the SC samples during storage. Yellowness (b*)] values of the SC samples during storage. Redness Viscosities of all the SC samples significantly decreased at the end (a*) of the samples showed an insignificant (p < .05) decrease as of the storage period (p < .05). As the storage period increased there the storage period increased. There were significant reduction was significant differences (p < .05) between the SC samples. SC was 8 of 11 | ADELEKE Et AL. FIGURE 1 Changes in chemical properties of SC from cassava starches during storage FIGURE 2 Changes in colour parameters of SC from cassava starches during storage | ADELEKE Et AL. FIGURE 3 9 of 11 Changes in apparent viscosity of SCs from cassava starches during storage TA B L E 6 Microbial load (cfu/g) of SC samples made from cassava starch for fresh and stored samples Storage period Samples 0 2 1 c 3 b 12.05 ± 0.78a TMS 01/1368 ND 4.45 ± 2.19 TMS 01/1371 ND 4.50 ± 2.40 c 13.25 ± 1.06b 19.50 ± 3.53a TMS 96/1632 ND c 4.90 ± 0.42 b 13.30 ± 0.14a TMS 01/1412 ND 5.80 ± 2.78ab 10.50 ± 3.54a 13.00 ± 1.41a b 25.00 ± 1.41a 11.75 ± 0.35a 12.25 ± 0.35a b 24.50 ± 0.71a 16.00 ± 8.49a 15.10 ± 0.14a c TMS 01/1206 ND 1.85 ± 0.78 TMS 30572 ND 6.30 ± 5.23ab c TMS 98/0581 ND 5.50 ± 2.40 TME 419 ND 5.65 ± 3.32a 8.25 ± 1.06 9.00 ± 1.13 14.35 ± 0.49 14.50 ± 0.70 Note: Mean values having different superscripts within the same column are significantly different (p < .05) ND = Not detected *0 month (×102), 1 month (×102), 2 months (×102), and 3 months (×103) not continuously sheared during storage, that is the fluid becomes thinner, rather than thicker during storage. Moreover, the shear thin- 3.9 | Microbial quality changes in SC from cassava starches during storage ning is a transient behavior. Once the force is removed, the viscosity is lost. Loss of viscosity could have been caused by molecular dis- The microbial load of the SC samples made from cassava starch is shown integration resulting from chemical (starch, oil, protein) changes as in Table 6. Freshly prepared SC samples had no viable microbial cell. earlier mentioned. As it was noted that between the cassava varie- However, the TPC increased with storage period and these were signifi- ties, differences were also observed. cantly different (p < .05) among the SC samples. Spoilage in mayonnaise Increase in speed were seen to affect all the samples irrespec- and salad dressings results from a variety of causes including separation tive of the variety, which is similar to the findings of Kahn, Frankel, of the emulsion, oxidation, and hydrolysis of the oils by chemical or bio- Snyder, and Potter (1990) for sweetened concentrated dislodge soy logical action, and growth of microorganisms that produce gas or off-fla- beverage. vors. Smittle (2000) reported that dressing products are rarely associated 10 of 11 | ADELEKE Et AL. with foodborne illness due to their acidic nature. However, the increase significant correlations. The most interesting are the correla- in TPC at the end of the storage period (3 months) reported in this study tions between the total plate counts (TPC1 and TPC2) of stored may be due to the growth of acid tolerant microorganisms such as lactic samples and the TS, TTA, and PV of the freshly prepared sam- acid bacteria (Karas et al., 2002). According to the “Microbiological guide- ples. TS, TTA, and PV are strictly subject of ingredient formula- lines for ready to eat foods”: Center for food safety (May, 2007), the TPC tion. The results clearly indicate the preservative ability of the 4 for mayonnaise or salad dressings should be less than 10 cfu/g for it to formulation used against the microbial deterioration of the SC. be classified as satisfactory (Class A; CFS, 2015). The values for the TPC The significant positive correlation between TPC and TS shows from this study are less than 104 even after 3 months of storage. This that formulation with less solid content could help slow down indicates that the SCs samples were relatively stable to microbial growth. the proliferation of aerobic organisms in the product during The linear regression of viscosity changes in SC samples made storage. On the contrary, increased acidity could slow down mi- from cassava starch with storage time is shown in Table 7. It was crobial proliferation. Vinegar is the main source of acidulation observed from this study that the slope of all the SC samples were of SC whereas starch inclusion is the main source total solid in negative and this showed that viscosity of the SCs decreased with the formulation. This outcome further indicates that subsequent storage period, which indicates that the textural stability of the SC studies to optimize fresh and store sample qualities of cassava samples varied significantly (p < .05) with TMS 1206 having the most starch based SC needs to consider these as important variable stable flow properties while TMS 1371 had the least. to balance their antagonistic effects on the microbial stability of the product. The PV of fresh SC is solely dependent on the quality of oil used. The positive correlation between PV and TCP 3.10 | Pearson's linear correlation between the chemical properties, microbial, and viscosity of the SC further establishes the fact that the major microbes that dominate the SC during storage are likely to be the aerobic. Increased peroxidation of the growth medium could have increased oxygen Table 8 shows the linear correlation between the properties potentials of the medium. of SC determined in this study. Apparently, there are very few TA B L E 7 Linear regression of apparent viscosity changes in SC sample with storage time 4 | CO N C LU S I O N S Samples Slope Intercept R2 TMS 01/1368 −623.93 2,951.7 0.9902 of eight cassava roots had significantly different physical, chemi- This study has shown that SC samples produced from starches TMS 01/1371 −960.97 3,805.7 0.8317 cal, and rheological properties. Viscosities of the SCs were Non- TMS 96/1632 −315.37 1,890.8 0.8668 Newtonian and the stored SC samples had significantly different TMS 01/1412 −389.00 2,257.3 0.8399 TMS 01/1206 −289.00 1879.1 0.8820 TMS 30572 −537.10 2,508.1 0.9092 TMS 98/581 −327.50 1825.5 0.9179 TME 419 −745.37 3,013.0 0.9985 TA B L E 8 pH TS TTA PV TPC1 TPC2 TPC3 textural stability. Within the 3 months storage period, the SC samples were all chemically and microbiologically stable based on the standards for PV and TPC. The levels of stabilities were based on cassava variety. The most stable SC from textural point of view was derived from a yellow fleshed cassava variety (TMS 1206). Correlation between the chemical properties, microbial and viscosity of the SC samples pH TS TTA PV TPC1 1.000 0.426 −0.123 −0.468 1.000 0.402 −0.382 0.871 −0.239 −0.622 0.468 0.197 0.047 1.000 −0.611 0.031 −0.713 −0.598 0.319 0.072 −0.038 1.000 −0.254 0.707 0.418 −0.293 −0.247 −0.296 1.000 −0.116 −0.579 0.410 0.181 0.085 1.000 0.662 −0.169 0.025 0.092 1.000 −0.647 −0.346 −0.181 1.000 0.908 0.789 1.000 0.964 0.546 TPC2 0.033 TPC3 V30 V60 −0.032 −0.101 −0.045 V30 V60 V100 V100 0.076 1.000 Note: Correlation coefficients in red are significant at p < .05, Correlations in dark red are significant at p < .01. Abbreviations: TS, total solid (%); TTA, total titratable acidity (%); PV, peroxide value; TPC1, total plate count after 1 month; TPC2, total plate count after 2 months; TPC3, total plate count after 3 months; V30, viscosity at 30 rpm; V60, viscosity at 60 rpm; V100, viscosity at 100 rpm. | ADELEKE Et AL. AC K N OW L E D G M E N T S The study is an output of the Cassava Web Innovation work package of the BiomassWeb Project funded by the German Federal Ministry for Education and Research (BMBF) and the Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH. The Research Fellowship offered by the International Institute of Tropical Agriculture, Ibadan, Nigeria to the first author is gratefully acknowledged. C O N FL I C T O F I N T E R E S T The authors have declared no conflicts of interest for this article. ORCID D. M. Adeleke https://orcid.org/0000-0003-4452-436X REFERENCES Adebayo, G. B., Otunla, G. A., & Ajao, T. A. (2009). 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