Effect of surface coating with seeds mucilages and xanthan gum on oil uptake and physical properties of fried potato strips

Abstract The oil uptake and high‐fat/oil content problem associated with fried food products can be decreased using polysaccharides (mucilages and gums) as edible coatings. In this study, the efficiency of seeds mucilages (Balangu, Basil, and Wild sage), and xanthan gum as edible coatings on the oil uptake, moisture retention, and physical properties (color indexes and surface shrinkage) of potato strips during oil frying have been examined. Coating treatment with seeds mucilages and xanthan gum significantly decreased the moisture loss and oil uptake of potato strips (p < .05). Lightness (L*) index values of uncoated‐control and coated potato strips decreased during frying. The lowest and highest color change intensity (∆E) and surface shrinkage (%) values were observed for the potato strips coated by Wild sage seeds gum and uncoated‐control sample, respectively. The MMF (Morgan‐Mercer‐Flodin) model was selected as the best equation for describing the color changes intensity kinetics of untreated and treated potato strips during frying. The appropriate coating suspension for reducing the oil content of fried potato strips and improving product appearance quality was 1.0% Wild sage seeds gum.

as Balangu, Basil, and Wild sage seed gums including biodegradable properties, eco-friendliness, low extraction and production cost, accessibility, hydrophilic nature, and appropriate rheological characteristics caused high interest to more application as coating material (Amini et al., 2021). These gums have the suitable physical properties as an edible coating for enhancement of appearance quality of fried food products. Also, these seed gums are able to lower the migration of lipids (Salehi, 2020).
The surface color and appearance quality of the fried food products are one of the highest significant quality factors for the acceptance of these products. Also, the surface color measurements of fried foods (during frying procedure) can be used in an indirect way to determine the product appearance change, since they are simpler and faster than chemical analysis (Salehi, 2018(Salehi, , 2020. Kurek et al. (2021) investigated on the efficiency of coatings treatment with carboxymethyl cellulose, chitosan, pectin and arabic gum, and natural antioxidants on fresh-cut potato's color, pH, moisture content, stability, and oil uptake after deep fat frying. The authors reported that the coatings significantly decreased oil content in deep fat fried potato strips, without effects on L*, b*, whiteness index, and ΔE. In addition, Kizito et al. (2017) reported that the hydrocolloid coatings (carboxymethyl cellulose, pectin, agar, and chitosan) of potato strips decreased the quantity of oil uptake by samples by 12.93% (pectin), 11.71% (carboxymethyl cellulose), 8.28% (chitosan), and 5.25% (agar). Also, hydrocolloid coating treatments and concentration (1 and 2%) significantly decreased moisture loss of strips (p < .05).
Process variables include fryer type, frying temperature and condition, sample pretreatment, and edible coatings are expected to affect the color and surface of the fried products (Salehi, 2020).
While there are many literature studies on the oil uptake and moisture content of uncoated fried food products, no studies related to the moisture content, oil uptake, color indexes change (L*, a*, b*, and ΔE), and surface area change during frying of coated potato strips with seeds gums (Balangu, Basil, and Wild sage) were found in the literature. Therefore, the objective of this work is to examine the moisture content, oil uptake, and kinetics of color change and shrinkage during frying of coated potato strips with Balangu seeds, Basil seeds, Wild sage seeds, and xanthan gums.

| Potato strips preparation
Potatoes were harvested in a patch located in Hamedan, Iran.
Potatoes were hand-peeled, cut with a oval-shaped mold (strips), and knife into strips with 1 cm thickness.

| Seeds gum powder preparation
The cleaned Balangu seeds, Basil seeds, and Wild sage seeds were firstly immersed in distilled water at the seed/water ratio of 1:20, at 25℃, and for 20 min. Gums extract was separated from the swollen seeds by passing the seeds through a extractor equipped (Panasonic, MJ-J176P). The extracted gums were then dried in an air-forced oven (Shimaz) at 60℃, and finally, the gums powder was milled, sieved, packed, and kept in dry condition at 20℃ (Amini et al., 2021;Satorabi et al., 2021).

| Coating of potato strips
Edible coating is the one of the ways to decreasing the oil uptake of fried potato strips. In this study, Balangu seeds, Basil seeds, Wild sage seeds, and xanthan gums were used to coating the fresh potato strips before frying. A 1.0% (w/w) of each gums solutions were prepared at 25℃, and then potato strips were immersed for 1 min in these solutions ( Figure 1).

| Frying condition
Fresh refined sunflower oil (Bahar frying oil) was used as a frying medium for each frying batch. After potato strips were soaked in gums solutions for 60 s, they were inserted to the sample holder, which were then immersed in hot oils in a mini fryer (Delmonti, DL630). They were followed by frying at 180ºC for 1-12 min and cooling down at 20℃ for 4 min. Also, K-type thermocouples F I G U R E 1 Schematic of coating and frying process of potato strips (thermocontroller, ±0.1℃, Lutron, TM-916) with a 1-s response time were used in measuring temperatures.
The weight changes of the potato strip samples were measured using a digital balance (LutronGM-300p) with an accuracy of ±0.01 g. The values of total solid and moisture content (MC) of fresh and fried potato strips were measured using an oven (Shimaz) at 105℃ for 5 hr (using Equation 1). The average moisture content of fresh potato strips was 79%.
In this equation, MC is the moisture content (%), M 1 is the initial weight of the samples (before oven) (g), and M 2 is the final weight of samples (after oven) (g). Also, the oil uptake (%) of fried potato strips was calculated using Equation 2: where OU is the oil uptake (%), TS 2 is the total solid of fried potato strips (g) (the final weight of fried potato strips, after oven), TS 1 is the total solid of fresh potato strips (g), and M 1 is the weight of each fried potato strip (g).

| Color and shrinkage
The samples' photos were captured with a scanner (HP, Scanjet-300).
The ΔE (color changes intensity) values for the total color difference were determined using Equation 3: The shrinkage (area) change of the potato strips during frying procedure was determined using Equation 4: where ΔA is the shrinkages change (%), and A 0 and A t (cm 2 ) are the area of the fresh potato strips and the fries samples at frying period of t, respectively.

| Mathematical modeling
In this study, the power, quadratic, and sigmoidal models (Gompertz relation, logistic model, Richards model, MMF (Morgan-Mercer-Flodin) model, and Weibull model) were selected to characterize the color changes intensity within the frying process of uncoatedcontrol and coated potato strips with Balangu seeds, Basil seeds, Wild sage seeds, and xanthan gums (Hyams, 1997;Salehi, 2019;).

| Statistical analysis
Significant difference between data means was estimated using Duncan's multiple range test at p-value<0.05 (SAS 9.1 Institute, Inc.), and it was carried out to establish the impact of edible coatings (coating with Balangu, Basil, and Wild sage seeds mucilages and xanthan gum) on the moisture content, oil uptake, color indexes (a*, b*, L*, and ∆E), and surface area changes of fried potato strips (pvalue < .05). The results will be compared with uncoated-control potato strips. All frying experiments and samples analysis were carried out in triplicate.

| RE SULTS AND D ISCUSS I ON
It is generally recognized that oils are absorbed in food products during frying by water evaporation as well as water vapor condensation. Edible coatings applied to foods before frying are a technique that can increase the quality and overall acceptability of fried potato strips. Figure 2 demonstrates the influence of coatings with Balangu seeds, Basil seeds, Wild sage seeds, and xanthan gums on the moisture content and oil uptake of fried potato strips. The moisture content was 39.12 for the uncoated-control samples, while 42.87, 41.75, 44.17, and 41.66 were determined for fried samples coated with Balangu seeds, Basil seeds, Wild sage seeds, and xanthan gums, respectively. The coated potato strips had high moisture content due to the inhibitory influences of the seeds gums and xanthan gum compared to the untreated samples. The results showed that seeds gums and xanthan gum could increase moisture retention and decrease oil uptake of deep fried potato strips (p < .05). There was no significant difference between coated potato strips with seeds gums and xanthan gum in oil uptake (p > .05). Naji Tab asi and Mahdian (2017) and Karimi and Kenari (2016) also observed a similar trend of low oil uptake during frying of treated potato chips with Persian gum and treated potato strips with Basil seed gum and salep, respectively. Khazaei et al. (2016) observed that the treatment with Basil seed gum and thymol improved the appearance of the fried shrimps and also the least oil uptake and the highest moisture content in the total frying duration and at different condition were reported for these coated samples. Also, Eslampour and Hosseini (2017) 86, 20.99, 17.45, and 19.29 were found for fried strips treated with Balangu seeds, Basil seeds, Wild sage seeds, and xanthan gums, respectively.
Kinetics modeling of color change intensity is necessary tools for the optimization of frying conditions and controlling or improving the process to get high quality of the fried products. The various equations were fitted to the color change intensity values and the calculation of the parameters, resulted from fitting models to the empirical data. The results of fitting the MMF model (Equation 5) to the empirical data are collected in Table 1.
where ΔE and t are the color changes intensity and frying duration,

| CON CLUS ION
The influence of Balangu seeds, Basil seeds, Wild sage seeds, and xanthan gums as edible coatings on the oil uptake and color change kinetics of potato strips during frying has been studied. oil content of fried potato strips and improving product appearance quality was 1.0% Wild sage seeds gum.

CO N FLI C T O F I NTE R E S T
We have no conflict of interest to declare.

E TH I C A L A PPROVA L
This study does not involve any human or animal testing.

DATA AVA I L A B I L I T Y S TAT E M E N T
All data generated or analyzed during this study are included in this published article.

I N FO R M E D CO N S E NT
Written informed consent was obtained from all study participants.
The manuscript is not submitted or under consideration in any other journals.