The value of the native potato varieties grown in Argentinean northwest lies both in their fundamental role as a source of food for the population and in their potential for the development of new products. The aim of this work was to study the changes produced by two common cooking processes (boiling and frying) on the nutritional, textural and functional characteristics of five Andean potatoes varieties. The cooking process (boiling) does not significantly affect the composition of potatoes, but there are losses of vitamin C; a greater loss was observed when they were boiled shelled. In frying potatoes vitamin C is completely destroyed. Resistant starch values between 0.90 and 4.58 g/100g of potato were found for raw Andean varieties; they decreased during the cooking process (boiled) (0.15 to 0.54 g/100g of potato) and increased again to be stored for 48 h at 4 °C (0.73 - 1.88 g/100g of potato). The frying process produced an increment in energy value between 92% and 148% according to variety. Regarding to the fracture strength and hardness, no significant differences were observed between the Andean varieties and the control (Spunta) at the initial or final stages, but there were differences during the intermediate stages.
Potatoes are tubers whose nutritional value has been underestimated. They are an important food source worldwide, mainly as a source of energy and some micronutrients. According to statistics from FAOSTAT FAO [
Modern methods of food production play an important role in reducing the genetic diversity of plants and animals, whereby FAO [
Starch is the main component in potatoes’ dry matter; this is important for food industry due to the effect it has on the physical, functional and organoleptic properties of food. In the last years, search for alternative sources of starch was deepened to the conventional maize and wheat, which possess the desirable functional properties for industrial application [
Based on its digestibility, starch is classified into readily digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) [
Potato varieties differ from one another in their texture after cooking. This feature, which involves consistency, tendency to rupture, flouriness, dryness and structure, frequently determines the use to be given to the product [
A common way to consume potatoes is boiled and fried. Frying is a widespread method in the food industry. It improves the hygienic quality of food by the inactivation of pathogenic microorganisms, develops pleasant organoleptic characteristics in food through non-enzymatic browning reactions and may increase the digestibility and bioavailability of nutrients in the digestive tract. It can be defined as the food cooking and dehydration by immersion in hot medium―oil. The high temperatures and the presence of water, oil and/or hot air cause several changes of food components during processing: hydrolytic and interesterification reactions, enzymatic and non- enzymatic browning, oxidation, oil degradation during frying, formation of flavor or smell-taste perception, degradation of natural pigments and formation of colored compounds.
Food composition databases should contain information about the food as ingested; and potatoes are eaten cooked [
The aim of this work was to study the changes produced by two common cooking processes (boiling and frying) on the nutritional, textural and functional characteristics of five Andean potatoes varieties.
Five varieties of Andean potatoes (S. tuberosum ssp. Andigenum) were studied: Collareja, Runa, Churqueña, Imilla Colorada and Revolution, purchased from Agricultural and Artisanal Cooperative Union Quebrada and Valleys (CAUQueVa). Crops were brought by local producers to the collection and these were classified and kept refrigerated. Six samples of 2 Kg for each variety were selected (two samples of each at three different times) and kept refrigerated until use. All determinations were performed in triplicate. The Spunta (S. tuberosum) variety was used as a reference because it is the most widespread commercially. It was provided by the Estación Experimental Agrícola “Obispo Colombres”, Tafí del Valle, Tucumán. Argentina.
The samples were peeled using a kitchen vegetable peeler, and were cut into thin strips. All the analytical determinations were performed using AOAC methods [
It was determinate according to Correa de Souza et al. [
For vitamin C extraction of the food matrix, the sample was mashed and homogenized with a solution of meta-phosphoric (0.3 M) and acetic acid (1.4 M). The extracts were filtered and used for their quantification.
Potatoes (with and without shell) were placed in a container of boiling water. They were boiled for 20 min. After this time, the potatoes were removed and the vitamin C content was determined. The factor of retention of Vitamin C was calculated according to the recommendations of FAO [
RFVitC = VitC [mg/100g boiled potato] × YF × 100
VitC [mg/100g raw potato]
YF = weight boiled potato (g)/weight raw potato (g)
It was determined according to the technique described by McCleary et al. [
It was determined in raw potatoes, freshly boiled potatoes (boiled for 20 minutes) and boiled potatoes stored at 5˚C for 48 hours, by the technique of Goñi et al. [
The potatoes were cut (1.2 × 1.2 × 3.0 cm) with a commercial potato cutter (French FryCutter). For the frying process, a domestic electric fryer (Phillips) with glass aluminum, 2.5 L capacity and temperature controller was used. The frying time was 5 min/300g of food at an initial oil temperature of 196˚C ± 2˚C, the temperature and cooking time was previously set to obtain a product of acceptable color and texture. Partially hydrogenated vegetable oil (®Superfry) was used, the oil/feed relation was 833 mL/100g.
All determinations were performed in quadruplicate.
Fat Absorption (FA)It was calculated using Bognár & Piekarski [
Fat absorption (%) = Fat fried food (%) × Yield − Raw food fat (%)
Yield = Weight fried food/weight raw food
Potatoes of similar sizes were selected, weighed and dipped in boiling water, whole and with their skin, for 5, 10, 15 and 20 minutes after the water began to boil again. When each cooking period was completed, the potatoes were brought to room temperature by immersion in cold water. The food/water ratio was 90 - 210 g/L.
The cooking time was established as the required to reach the lowest compression strength needed to attain 50% of the thickness of the original slice [
Three potatoes were taken from each established boiling time batch and two 1-centimeter-thick slices were cut. Fracture strength and hardness were measured with a CNS Farmell QTS 25 Texture Analyzer belonging to the National University of Salta.
The established compression distance was 50% of the total height of the slices (0.5 cm), with a speed of 50 mm/min and a cell pressure of 10 kg.
Samples of potatoes boiled for 5, 10, 15 and 20 minutes were brought to room temperature by immersion in cold water, dried and weighed again.
Two aliquots of 40 mL were taken of the cooking water and dried at 105˚C.
Raw potato | |||||||
---|---|---|---|---|---|---|---|
Variety | Moisture (g/100g potato) | Energy (Kcal/kJ) | Protein | Lipid | Ash | Total fibre | Carbohydrateb |
(g/100g potato)a | |||||||
Spunta | 82.94 ± 1.49 | 57/239 | 1.98 ± 0.78 | 0.05 ± 0.03 | 0.84 ± 0.14 | 2.01 ± 0.10 | 12.18 |
Collareja | 75.87 ± 3.69 | 82/344 | 2.47 ± 0.51 | 0.12 ± 0.04 | 1.16 ± 0.03 | 2.57 ± 0.17 | 17.81 |
Revolución | 78.28 ± 1.82 | 75/314 | 0.85 ± 0.06 | 0.07 ± 0.03 | 1.01 ± 0.07 | 1.95 ± 0.09 | 17.84 |
Churqueña | 73.58 ± 2.75 | 92/385 | 2.23 ± 0.73 | 0.47 ± 0.42 | 1.02 ± 0.03 | 2.84 ± 0.13 | 19.86 |
I. Colorada | 73.07 ± 0.63 | 97/406 | 2.55 ± 0.41 | 0.51 ± 0.28 | 1.35 ± 0.24 | 1.98 ± 0.11 | 20.54 |
Runa | 74.91 ± 3.69 | 85/356 | 1.60 ± 0.50 | 0.26 ± 0.11 | 0.89 ± 0.23 | 3.30 ± 0.15 | 19.04 |
Boiled potato | |||||||
Variety | Moisture (g/100g potato) | Energy (Kcal/kJ) | Protein | Lipid | Ash | Total fibre | Carbohydrateb |
(g/100g potato)a | |||||||
Spunta | 82.97 ± 0.00 | 57/239 | 1.97 ± 0.00 | 0.05 ± 0.01 | 0.84 ± 0.050 | 2.00 ± 0.12 | 12.17 |
Collareja | 76.60 ± 0.25 | 79/331 | 2.40 ± 0.03 | 0.12 ± 0.00 | 1.13 ± 0.01 | 2.50 ± 0.03 | 17.25 |
Revolución | 78.74 ± 0.04 | 74/310 | 0.83 ± 0.00 | 0.07 ± 0.02 | 0.99 ± 0.07 | 1.91 ± 0.05 | 17.46 |
Churqueña | 73.96 ± 0.10 | 91/381 | 2.20 ± 0.01 | 0.46 ± 0.06 | 1.01 ± 0.09 | 2.80 ± 0.01 | 19.57 |
I. Colorada | 73.57 ± 0.07 | 95/398 | 2.50 ± 0.01 | 0.50 ± 0.02 | 1.32 ± 0.11 | 1.94 ± 0.11 | 20.17 |
Runa | 75.40 ± 0.13 | 83/348 | 1.57 ± 0.01 | 0.25 ± 0.00 | 0.87 ± 0.01 | 3.21 ± 0.02 | 18.70 |
Fried potato | |||||||
Variety | Moisture (g/100g potato) | Energy (Kcal/kJ) | Protein | Lipid | Ash | Total fibre | Carbohydrateb |
(g/100g potato)a | |||||||
Spunta | 64.75 ± 1.58 | 141/591 | 4.09 ± 0.15 | 4.79 ± 0.52 | 1.74 ± 0.08 | 4.15 ± 0.32 | 20.48 |
Collareja | 57.74 ± 1.59 | 176/737 | 4.33 ± 0.13 | 6.72 ± 1.71 | 2.03 ± 0.10 | 4.50 ± 0.23 | 24.68 |
Revolución | 62.49 ± 2.43 | 159/666 | 1.47 ± 0.09 | 6.01 ± 1.22 | 1.74 ± 0.22 | 3.37 ± 0.14 | 24.92 |
Churqueña | 57.04 ± 5.92 | 177/742 | 3.63 ± 0.10 | 6.20 ± 0.76 | 1.66 ± 0.17 | 4.62 ± 0.42 | 26.85 |
I. Colorada | 55.33 ± 1.87 | 186/779 | 4.22 ± 0.21 | 5.92 ± 1.25 | 2.24 ± 0.13 | 3.28 ± 0.26 | 29.01 |
Runa | 52.12 ± 1.50 | 186/779 | 3.05 ± 0.30 | 5.45 ± 0.51 | 1.70 ± 0.05 | 6.30 ± 0.20 | 31.38 |
aMean ± standard deviation; n = 3; bCarbohydrate = 100 − (Moisture + Protein + Lipid + Ash + Total fiber).
Variety | Raw | Boiled in shell | Boiled shelled | ||
---|---|---|---|---|---|
Vitamin Ca (mg/100g potato) | Vitamina Ca (mg/100g potato) | Retention (%) | Vitamina Ca (mg/100g papa) | Retention (%) | |
Spunta | 28.58 ± 1.93 | 17.65 ± 0.87 | 63.19 | 16.35 ± 0.42 | 58.52 |
Collareja | 15.61 ± 0.04 | 8.36 ± 0.53 | 54.91 | 5.45 ± 0.55 | 35.82 |
Revolución | 11.00 ± 2.76 | 7.97 ± 1.17 | 73.56 | 6.58 ± 0.11 | 60.68 |
Churqueña | 12.74 ± 0.03 | 10.78 ± 1.29 | 86.09 | 8.11 ± 0.21 | 64.74 |
Imilla Colorada | 9.01 ± 0.07 | 7.25 ± 0.37 | 81.85 | 6.42 ± 0.11 | 72.59 |
Runa | 10.86 ± 0.93 | 7.50 ± 0.42 | 68.02 | 5.00 ± 0.14 | 46.91 |
aMean ± standard deviation; n = 3.
found retention factors between 56% and 97% in Peruvian native varieties. Different FR found for vitamin C may be related to the type of shell of each of the varieties studied, which could act as a protective barrier for the loss of nutrients. The variation in the content of vitamin C and the retention rates obtained are coincident with the values reported by Murniece et al. [
Cooking processes in wet conditions produce loss in the content of water-soluble vitamins and significantly improved the digestibility of starch, which must be made with controlled times. To minimize the loss of water soluble nutrients it is recommended eating the potato with shell by the barrier action exerted.
There is great interest to nutritionists and food industry to know properties of resistant starch (RS), which have led to extensive research on the contribution of the non-digestible carbohydrate components of the diet and their physiological implications. Colonic fermentation, bacterial growth, the post-prandial blood glucose level, intestinal transit time and the energy values of foods are affected by the presence of RS. The RS content in raw potatoes is determined by the physical encapsulation of starch granules. The boiling process modifies the resistant starch in food.
The increase of RS during stored of boiled potatoes could be attributed to the retrogradation of amylose, although it has been demonstrated that amylopectin may also become retrograded and contribute to RS content [
Variety | Total starcha (g/100g) wmb | Rawa | Boileda | Boiled and storeda |
---|---|---|---|---|
Resistant starch (g/100g) wmb | ||||
Spunta | 12.61 ± 0.22 | 2.47 ± 0.07 | 0.23 ± 0.05 | 2.85 ± 0.17 |
Revolución | 16.47 ± 0.15 | 4.58 ± 0.18 | 0.54 ± 0.04 | 0.97 ± 0.10 |
Churqueña | 18.70 ± 1.01 | 0.71 ± 0.07 | 0.50 ± 0.04 | 0.86 ± 0.02 |
Runa | 15.66 ± 1.24 | 0.90 ± 0.10 | 0.30 ± 0.05 | 0.79 ± 0.01 |
Imilla Colorada | 13.53 ± 0.08 | 1.44 ± 0.12 | 0.14 ± 0.02 | 0.73 ± 0.15 |
Collareja | 15.82 ± 0.27 | 0.90 ± 0.14 | 0.15 ± 0.03 | 1.88 ± 0.30 |
aMean ± standard deviation; n = 3; bWet mater.
Variety | Moisture loss | Fat absorption |
---|---|---|
(g/100g potato)a | ||
Spunta | 19.63 ± 0.20 | 2.63 ± 0.02 |
Collareja | 25.21 ± 0.16 | 4.00 ± 0.06 |
Revolución | 20.80 ± 0.11 | 3.62 ± 0.09 |
Churqueña | 21.82 ± 0.21 | 3.91 ± 0.10 |
I .Colorada | 24.36 ± 0.17 | 3.61 ± 0.01 |
Runa | 27.41 ± 0.27 | 3.43 ± 0.04 |
aMean ± standard deviation; n = 3.
The fat content of raw and fried potatos found (
Moisture loss and fat absorption (
To evaluate the textural properties of cooked potatoes imitative type tests were used, which simulate mastication using mechanical instruments being the most used the Texture Profile Analysis (TPA). The cooking time was determined by analyzing the behavior of the compression strength as a function of time that tubers are kept at boiling. When the compressive strength is kept constant it is considered that the tubers are cooked and apt to consume.
Both parameters exhibit the same behavior; remaining high until 10 minutes for Andean varieties while for Spunta variety it falls faster. For Rune variety fracture strength drops at 5 min and then remains practically con-
stant. The Spunta variety presents the lowest initial fracture strength although the difference with respect to the Andean varieties is not significant.
According to García-Segovia et al. [
Adhesiveness may be related to the strength needed to remove the potato that remains adhered to the palate and teeth after mastication [
According to Garcia Segovia et al. [
The amount of water absorbed is less than 3% at 20 min for reference and Andean varieties, and are slightly lower than those reported by Kaur et al. [
The loss of soluble solids remains constant throughout the cooking cycle (
Water absorption is inversely proportional to the preservation of nutrients. Higher water absorption increases the probability of nutrients to be solubilized and the loss is higher during cooking (boiling) [
The boiling process affects the composition of the Andean potato producing losses of vitamin C; the cooking by frying destroys vit C and increases the energy value of fried food; the increase depends on the variety of the potato. It can also be affirmed that the boiling process decreases the RS content in different varieties of potatoes; and that during storage at 4˚C it increases again.
Texture analysis of boiled potatoes shows that there is no difference between boiled Andean varieties and reference variety.
Variety | Adhesiveness [J]a | ||||
---|---|---|---|---|---|
0 min | 5 min | 10 min | 15 min | 20 min | |
Spunta | −0.75 ± 0.17 | −0.20 ± 0.56 | −0.23 ± 0.86 | −0.13 ±0.06 | −0.10 ± 0.04 |
Revolución | −0.56 ± 0.24 | −0.56 ± 0.18 | −0.23 ± 0.61 | −0.22 ± 0.09 | −0.17 ± 0.02 |
Churqueña | −0.62 ± 0.20 | −0.20 ± 0.58 | −0.24 ± 0.50 | −0.23 ± 0.09 | −0.16 ± 0.03 |
Runa | −0.77 ± 0.32 | −0.56 ± 0.13 | −0.24 ± 0.85 | −0.21 ± 0.02 | −0.16 ± 0.06 |
I Colorada | −0.69 ± 0.14 | −0.19 ± 0.94 | −0.36 ± 0.19 | −0.23 ± 0.07 | −0.13 ± 0.07 |
Collareja | −0.78 ± 0.10 | −0.34 ± 0.17 | −0.25 ± 0.04 | −0.28 ± 0.01 | −0.15 ± 0.08 |
aThe results are presented as average ± standard deviation; n = 3.
This work was conducted with financial support from the Council of Science and Technology of the National University of Tucumán (CIUNT) and National Agency for Science and Technology.