Influence of Ultrasound Frequency as a Preliminary Treatment on the Physicochemical, Structural, and Sensory Properties of Fried Native Potato Chips

Abstract

Frying native potato chips produces snacks that are widely accepted, although they are associated with high fat content and the formation of potentially undesirable compounds. This study evaluated the effect of pretreatment with ultrasound at 28 and 40 kHz on the physicochemical, structural, and sensory properties of chips made from the Sempal and Agustina varieties. The chips were immersed in water and treated with ultrasound for 10 min before frying at 175 °C. Parameters such as moisture, fat content, water activity, color, reducing sugars, FTIR spectroscopy, SEM microscopy, and sensory acceptance by consumers were analyzed. Treatment with 40 kHz significantly reduced fat content (up to 22.07%), improved crispness, and promoted a more porous microstructure. A lower concentration of reducing sugars, greater brightness, and less darkening were also observed. Sensory evaluation showed that chips treated with 40 kHz were the most preferred and best rated in terms of texture and flavor. Finally, it was demonstrated that pretreatment with ultrasound at 40 kHz improved the technological and sensory quality of native potato chips, which would promote the value of these resources in healthy products.

1. Introduction

The potato (Solanum tuberosum) is one of the most important crops worldwide due to its culinary versatility, availability, and nutritional value [1,2,3]. Within this group, native potatoes stand out for their functional properties, genetic diversity, and unique characteristics. They also play a fundamental role in preserving ancestral agricultural practices [4,5]. Beyond their cultural value, these varieties represent a significant opportunity to develop differentiated products with high added value. Potato products, such as potato chips, are very popular due to their sensory characteristics, making them one of the most sought-after snacks worldwide [6,7]. The quality of these products is determined by attributes such as oil content, texture, and color, factors that, together with sensory perception, define their acceptance in the market [5,8].

The native potatoes (Solanum tuberosum spp. Andigena), grown mainly in the high Andean region, represent not only a cultural legacy but also an invaluable resource due to their nutritional and functional properties. These varieties, free of pesticides and grown organically, contain high levels of bioactive compounds such as polyphenols, anthocyanins, and flavonoids, which offer antioxidant and protective benefits against degenerative diseases [9,10,11]. In addition, their low reducing sugar content and high dry matter make them ideal raw materials for frying, as they minimize the Maillard reaction and reduce oil absorption. These characteristics not only improve the nutritional quality of the derived products but also optimize production processes by reducing energy consumption [5,12].

In recent years, ultrasound has established itself as a promising technology in the food industry due to its ability to modify the physical and chemical properties of food through acoustic cavitation. This phenomenon generates microbubbles that, when they collapse, produce changes in the cellular structure, improving heat and mass transfer [13,14]. Its application prior to frying has been shown to reduce oil absorption significantly, optimizing the nutritional profile of the product [15]. Ultrasound frequency is a key factor. Higher frequencies intensify cavitation and can generate greater cell disruption. However, they may also compromise the structural integrity of tissues. On the other hand, lower frequencies may be insufficient to induce relevant changes. This treatment affects essential properties of potatoes such as starch gelatinization, porosity, and final texture, impacting both physicochemical quality and sensory attributes, including flavor and crispness, which are fundamental aspects for consumer acceptance [13,15].

Several studies in the last decade have evaluated ultrasound as a pretreatment to improve the quality of fried snacks. The use of an ultrasonic probe at 20 kHz reduces oil absorption in potato slices [15], and its combination with convective drying achieves even greater reductions [13]. Ultrasound also decreases acrylamide formation in microwave-assisted vacuum-fried sweet potato chips [16]. At the same time, its application together with ohmic heating improves oil control and preserves color and texture in fried potatoes [17]. Ultrasound-assisted osmotic dehydration has also been shown to effectively reduce oil absorption and improve texture in fried vegetable snacks, reinforcing its potential to optimize the quality of vegetable-based products [18]. Furthermore, recent research has demonstrated that ultrasound pretreatments, alone or combined with other processes, can enhance frying efficiency, reduce structural damage, and maintain desirable sensory attributes in fried plant-based products [19]. In addition, market-scale data from commercial potato chips revealed that color difference and texture are strongly linked to consumer preference, while acrylamide content correlates with sugar levels [20]. These results confirm that ultrasound is a versatile technology to improve the quality of starch-rich and vegetable-based fried products.

Despite advances in the application of ultrasound in snacks, its use in native potatoes remains limited, leaving a gap in how their unique properties interact with this technology. This study hypothesizes that ultrasound, applied at different frequencies, improves the physicochemical, structural, and sensory properties of native potato chips. The objective was to study the best conditions for its industrial implementation, diversifying its use, and developing healthier and more sustainable products for the global market. The novelty and objectives are summarized as follows:

• Evaluate, for the first time, the effect of two fixed ultrasound frequencies (28 and 40 kHz) on the quality of native potato chips from the Sempal and Agustina varieties.
• Analyze changes in physicochemical, structural, and sensory properties induced by the pretreatment before frying.
• Discuss the balance between technological improvements and potential losses of phenolic compounds and antioxidant capacity at higher frequencies.
• Propose ultrasound as a sustainable alternative for the valorization of Andean native potatoes in the snack industry.

2. Materials and Methods

2.1. Materials

Two varieties of native potatoes were used: Sempal (purple flesh) and Agustina (yellow flesh with reddish tones), harvested in June 2023 in the district of San Jerónimo, province of Andahuaylas, department of Apurímac, Peru. Both varieties were supplied by the company SEMPAL S.R.L. The average agricultural yield reported was approximately 20 tons per hectare. The tubers were selected for their uniformity in size and stored at room temperature (20 °C) until their experimental processing. The extra virgin olive oil (Milolivos, Lima, Peru) used in frying was purchased from a local commercial establishment.

Reagents used for phenolic compound and antioxidant analysis: Folin–Ciocalteu reagent (Himedia, India), gallic acid (Anhydro, China), Trolox [6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid] (Sigma-Aldrich, Germany), DPPH [2,2-diphenyl-1-picrylhydrazyl] (Himedia, India), and 3,5-dinitrosalicylic acid (Himedia, India).

Salts and buffers: sodium carbonate (Na₂CO₃), commercially sourced Na-K tartrate (C₄H₄O₆KNa⋅4H₂O) (Spectrum, Canada), and commercially sourced sodium hydroxide (NaOH) (Emsure, Germany).

Solvents: petroleum ether (Spectrum, Canada), 80% methanol (Spectrum, Canada).

2.2. Obtaining Fried Chips from Native Potatoes

The Sempal and Agustina potato varieties were selected according to size, then washed by hand to remove impurities, and sliced using a GR-RECHEF electric slicer (GRONDOY, Villa el Salvador, Peru, manufactured in China) to obtain a uniform thickness of 1 mm ± 0.1. They were then cut with circular stainless-steel molds, 2.5 cm in diameter, to standardize the size. They were then placed in a DU-220S ultrasonic bath (ARGO LAB, Milan, Italy, Manufactured in China) with distilled water at 25 ± 2 °C at frequencies of 28 kHz and 40 kHz for 10 min. The choice of these two frequencies was based on the fixed options available in the ultrasonic bath used. Internal pilot trials showed apparent differences in cavitation intensity without causing excessive tissue degradation. The treatment time of 10 min was selected to achieve sufficient microstructural modification while, at the same time, avoiding excessive leaching of soluble compounds, following the criteria reported in previous studies on chips subjected to ultrasound pretreatments [13,15,16]. An untreated control was included. The slices were then dried superficially with paper towels to remove surface moisture and fried by immersion in extra virgin olive oil at a temperature of 175 °C for 200 s in a deep fryer (Whiteline, Victoria, Australia, Manufactured in China). They were then packaged in bilaminated aluminum foil and stored at room temperature (20 °C) until further analysis [5,13,15].

2.3. Preparation of Methanolic Extract

The flakes were degreased using petroleum ether in the Soxhlet system. To prepare the phenolic extract, the degreased flakes were crushed to a 0.2–0.5 g size in 20 mL of 80% methanol and left to stand for 24 h in the dark at room temperature (20 °C) to release the phenols [5].

2.4. Total Phenolic Compounds

The Folin–Ciocalteu method [21] was used with a gallic acid calibration standard. First, 900 µL of phenolic extract was placed in a test tube, then 2400 µL of ultrapure water (dilution factor of 3.666), 300 µL of 0.25 N Folin–Ciocalteu reagent, and 150 µL of 20% Na₂CO₃ were added. The mixture was left to react for 15 min at room temperature, protected from light. At the same time, the blank was prepared under similar conditions, except that ultra-pure water was used instead of the sample. Readings were taken at a wavelength of 755 nm using a UV–vis spectrophotometer (Genesys 150, Thermo Fisher Scientific, Waltham, MA, USA) [5].

$$TPC={\displaystyle \frac{X\times V\times DF\times 100}{m\times DM}}$$

(1)

where $TPC$ is the total phenolic content, $X$ is the concentration of the sample, $V$ is the volume of extract, $DF$ is the dilution factor, $m$ is the mass of the chip, and $DM$ is the dry matter content.

2.5. Antioxidant Capacity by DPPH

The DPPH method (2,2-diphenyl-1-picrylhydrazyl stable radical) was used with a calibration standard of the trolox reagent (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid). For this method, the spectrophotometer was zeroed with methanol, and the DPPH reagent solution was adjusted to 1.1 ± 0.02 absorbance at a wavelength of 515 nm. Next, 150 µL of phenolic extract was prepared with 2850 µL of adjusted DPPH reagent and left to react for 15 min at room temperature in test tubes protected from light. The blank was prepared with 150 µL of 80% methanol and 2850 µL of adjusted DPPH reagent. Readings were taken at 515 nm in a UV–visible spectrophotometer (Genesys 150, Thermo Fisher Scientific, Waltham, MA, USA) [5].

$$AC={\displaystyle \frac{X\times V\times 100}{m\times DM}}$$

(2)

where $AC$ is the antioxidant capacity, $X$ is the sample concentration, $V$ is the extract volume, $m$ is the sample mass, and $DM$ is the dry matter content.

2.6. Reducing Sugars

The potato chips (0.4 g to 0.5 g) were crushed, added to a Falcon tube with 20 mL of ultra-pure water, shaken in a vortex at 3000 rpm for one minute to homogenize, and centrifuged in a refrigerated centrifuge (TDL-5M, BIORIDGE, China, Shanghai) for 3 min at 3500 rpm. From the supernatant, 0.5 mL of the sample was extracted, and 0.5 mL of DNS reagent (3,5-dinitrosalicylic acid) was added. It was then placed in a water bath at 100 °C for 5 min. It was cooled to room temperature, to add 5 mL of ultrapure water, homogenized with a vortex, and read in a UV–visible spectrophotometer (Genesys 150, Thermo Fisher Scientific, Waltham, MA, USA) at 540 nm. The results are expressed in mg of fructose/g of sample on a dry basis [5,22].

$$RS={\displaystyle \frac{X\times V\times 100\%}{m\times DM}}$$

(3)

where $RS$ is the reducing sugars, $X$ is the sample concentration, $V$ is the dilution volume, $m$ is the sample mass, and $DM$ is the dry matter content.

2.7. Water Activity (Aw)

Aw was measured at a temperature of 24 to 26 °C using an AQUALAB 4TE tabletop water activity meter (Meter Group, Washington, DC, USA) with calibration [23].

2.8. Color Analysis

Color was determined using the CR-5 colorimetric refraction module (Konica Minolta, Tokyo, Japan). A Petri dish was used, and the samples were placed on it, covering the entire base of the dish, which measures 420 mm. The results were recorded in L*, a*, and b* color parameters [24].

2.9. Proximate Composition

Determined by AOAC (2012) standard methods, analyses were performed for moisture (AOAC 925.10), protein (AOAC 2003.05), fat (AOAC 923.03), fiber (AOAC 985.29), and ash (AOAC 960.52). Carbohydrates were determined by difference [25].

2.10. Fourier Transform Infrared Spectroscopy Analysis (FTIR)

The spectrum was taken using a Fourier transform infrared spectrophotometer equipped with an iS50 ATR attenuated total reflectance module (Thermo Fisher Scientific, Waltham, MA, USA). The IR range at a resolution of 8 cm⁻¹ of 32 scans was performed with advanced ATR correction for the diamond crystal with several bounces of 1, an angle of incidence of 45, and a sample refractive index of 1.5 [26].

2.11. Scanning Electron Microscopy (SEM) Analysis

Microphotographs of native potato flakes were taken using a Prisma E scanning electron microscope (Thermo Fisher Scientific, Czech Republic, Brno). The sample was prepared on an adhesive carbon tape and an aluminum sample holder with dimensions of 12.7 × 8 mm. The reading was performed under low vacuum conditions of 0.07 torr and a magnification of 100× [5,13,15].

2.12. Sensory Evaluation

The preference and acceptance test was carried out after three weeks of storage of the coded fried native potato chips. For this purpose, 5 g of the sample was prepared on a work table with dividers, in a well-lit, clean environment free of odors. The panelists were 80 untrained individuals (men and women) between the ages of 20 and 30, as this age group represents the highest consumption preference for this type of product. They were individuals capable of giving their consent to participate in the sensory test of native potato chips. For the sensory acceptability test of color, smell, taste, and texture, a five-point hedonic scale card and a preference card were used, asking which coded samples they preferred according to their sensory perception [5,24,26]. The sensory test was approved by the Research Ethics Committee of the Universidad Nacional José María Arguedas, under Resolution No. 230-2024-UNAJMA/CU.

2.13. Statistical Analysis

All statistical analyses were performed using OriginPro 2025b software (OriginLab Corporation, Northampton, MA, USA). One-way analysis of variance (ANOVA) was applied to evaluate significant differences between treatments, followed by Tukey’s test (p < 0.05) for multiple comparisons. For sensory data, normality was verified using the Kolmogorov–Smirnov test, and in the case of non-normal distribution, the non-parametric Friedman and Wilcoxon tests were applied. All analyses were performed in triplicate, and results were expressed as mean ± standard deviation.

3. Results and Discussion

3.1. Total Phenolic Compounds, Antioxidant Capacity by DPPH, Reducing Sugars, and Water Activity

The results are shown in

Table 1. Total phenolic compounds, antioxidant capacity by DPPH, reducing sugars, and water activity.

Frequency	Sempal					Agustina
	Total Phenolic Compounds (mg AGE/g)
	$\overline{\mathit{x}}$	±	s	*		$\overline{\mathit{x}}$	±	s	*
Control	5.47	±	0.01	a		2.01	±	0.07	a
28 kHz	2.22	±	0.01	b		1.78	±	0.02	b
40 kHz	2.19	±	0.02	c		1.53	±	0.02	c
	Antioxidant Capacity by DPPH (µmol ET/g)
Control	33.70	±	0.08	a		19.49	±	1.61	a
28 kHz	30.90	±	0.06	b		14.09	±	0.88	b
40 kHz	24.81	±	0.09	c		9.78	±	0.63	c
	Reducing Sugars (mg/100 g)
Control	33.92	±	0.05	a		83.86	±	0.18	a
28 kHz	30.79	±	1.16	b		60.28	±	1.11	b
40 kHz	25.68	±	1.71	c		59.28	±	0.47	b
	Water activity (Aw)
Control	0.62	±	0.01	a		0.37	±	0.01	a
28 kHz	0.55	±	0.02	b		0.33	±	0.02	b
40 kHz	0.36	±	0.02	c		0.32	±	0.01	b

Note: Values are expressed as mean ($\overline{x})$ ± standard deviation (s), with n = 3, corresponding to the number of replicates. (*) Different letters in the same column indicate a significant difference between treatments according to Tukey’s test (p ≤ 0.05).

. In the case of total phenolic compounds, a decrease was observed in both native potatoes as the ultrasound frequency increased. This behavior can be attributed to the acoustic cavitation generated by the ultrasound, which breaks down cell structures, releasing phenolic compounds and making them more susceptible to oxidation and degradation [27]. Previous studies have shown that increasing ultrasound frequencies intensifies the extraction of bioactive compounds by causing a more efficient breakdown of food cell walls, facilitating the release of these compounds into the surrounding medium [28,29]. Similarly, antioxidant capacity, measured by DPPH, also decreased with increasing ultrasound frequency. This trend is closely related to the reduction in phenolic compounds, the main contributors to antioxidant activity in native potatoes [5]. Higher ultrasound frequencies improved specific technological and sensory properties. However, they also reduced phenolic compound content and antioxidant capacity. This highlights the need to optimize processing conditions to preserve the functional quality of the product. In this regard, future research could evaluate combined treatments, such as ultrasound with acid immersion, or alternative technologies such as ohmic heating, in order to minimize these losses and maintain the bioactive profile [30,31,32,33].

As for reducing sugars, a significant decrease was observed with increasing ultrasound frequency. This phenomenon is related to the effect of acoustic cavitation, which breaks down cell structures and facilitates the release of soluble compounds, including reducing sugars, into the surrounding medium, promoting their degradation [27]. In addition, ultrasound generates microchannels in the potato tissue, increasing the contact surface and promoting mass transfer, which contributes to reducing the concentration of reducing sugars [28]. This is relevant from a technological point of view, since a lower content of these sugars minimizes the Maillard reaction during frying, reducing the formation of acrylamides and improving both the sensory quality and nutritional profile of the final product [34].

Finally, water activity (Aw) decreased significantly with increasing frequency. This reduction can be attributed to cell disruption and partial evaporation of bound water, facilitated by the heat and movement generated during acoustic cavitation [35,36]. Previous studies have shown that ultrasound can promote a redistribution of water in the food matrix, decreasing the fraction of free water while increasing structurally bound water. This phenomenon, attributed to the mechanical and thermal impacts of ultrasound, optimizes the efficiency of water removal during subsequent thermal processes, improving key parameters such as texture and product stability during storage [13,15].

3.2. Color Analysis

Color is an essential sensory attribute in fried flakes, as it directly influences the consumer’s perception of quality [5]. Its development is related to the Maillard reaction, which depends on the content of reducing sugars and amino acids or proteins present in the food [16,37]. The results are shown in

Table 2. Average chromatic parameters in native potato chips.

Frequency	Sempal					Agustina
	Lightness L*
	$\overline{\mathit{x}}$	±	s	*		$\overline{\mathit{x}}$	±	s	*
Control	30.51	±	0.51	a		41.15	±	0.29	a
28 kHz	31.76	±	0.55	b		42.49	±	0.34	b
40 kHz	32.31	±	0.37	b		44.04	±	0.41	c
	Chroma a*
Control	1.66	±	0.05	a		8.84	±	0.23	a
28 kHz	1.73	±	0.05	a		9.12	±	0.08	a
40 kHz	1.82	±	0.03	b		12.33	±	0.15	b
	Chroma b*
Control	−3.36	±	0.10	a		11.41	±	0.11	a
28 kHz	−3.00	±	0.06	b		10.05	±	0.05	b
40 kHz	−2.78	±	0.09	c		8.70	±	0.17	c

Note: Values are expressed as mean ($\overline{x})$ ± standard deviation (s), with n = 3, corresponding to the number of replicates. (*) Different letters in the same column indicate a significant difference between treatments according to Tukey’s test (p ≤ 0.05).

, where it can be seen that the average lightness (L*) increased with the increase in ultrasound frequency. This phenomenon can be attributed to acoustic cavitation, which promotes cell disruption and the release of starch and solids to the surface, improving light reflection and producing a lighter product. Higher brightness is associated with better quality in fried products, highlighting its sensory relevance [17].

On the other hand, the average chromatic parameters for a* and b* showed variations that reflect the impact of ultrasound on the surface pigments of the potatoes. The increase in a* may be related to greater exposure of carotenoid pigments, especially in Agustina, while the decrease in b* could be due to the degradation of sensitive pigments such as carotenoids and phenolic compounds. These changes, although moderate compared to L*, highlight the influence of ultrasound on pigment stability and the overall appearance of the product. These results are consistent with previous studies reporting similar effects in ultrasound-treated products, highlighting the need to optimize process conditions to preserve an adequate color balance [13,15,17].

3.3. Proximate Composition

The proximal analysis of fried native potato chips (Sempal and Agustina varieties) is presented in

Table 3. Proximate composition results.

Frequency	Sempal					Agustina
	Fat (%)
	$\overline{\mathit{x}}$	±	s	*		$\overline{\mathit{x}}$	±	s	*
Control	33.49	±	0.15	a		22.84	±	0.12	a
28 kHz	33.47	±	0.09	a		22.50	±	0.02	b
40 kHz	33.14	±	0.04	b		22.07	±	0.10	c
	Protein (%)
Control	5.50	±	0.10	a		5.52	±	0.13	a
28 kHz	5.93	±	0.13	b		6.36	±	0.14	b
40 kHz	5.99	±	0.12	b		6.86	±	0.11	c
	Carbohydrates (%)
Control	55.93	±	0.04	a		66.72	±	0.23	a
28 kHz	55.72	±	0.10	b		66.24	±	0.11	b
40 kHz	55.69	±	0.03	b		66.17	±	0.15	b
	Moisture (%)
Control	2.54	±	0.03	a		2.98	±	0.04	a
28 kHz	2.53	±	0.05	a		2.91	±	0.02	a
40 kHz	2.52	±	0.04	a		2.90	±	0.15	a
	Ash (%)
Control	2.53	±	0.15	ab		1.94	±	0.11	a
28 kHz	2.36	±	0.11	a		1.99	±	0.13	a
40 kHz	2.66	±	0.14	b		2.00	±	0.12	a

Note: Values are expressed as mean ($\overline{x})$ ± standard deviation (s), with n = 3, corresponding to the number of replicates. (*) Different letters in the same column indicate a significant difference between treatments according to Tukey’s test (p ≤ 0.05).

. Significant differences (p ≤ 0.05) were observed in some of the components evaluated depending on the ultrasound treatment, particularly in fat and protein content. At the same time, the other properties studied did not show statistical differences.

Regarding fat content, a decreasing trend was observed as the ultrasound frequency increased. For the Agustina variety, the reduction was more pronounced (from 22.84% in the control to 22.07% at 40 kHz), demonstrating lower oil absorption during frying. This behavior can be attributed to the effect of ultrasound on the microstructure of the tissue, where the cavitation generated, especially at higher frequencies, promotes the formation of porous channels and a denser surface that facilitates water evaporation and limits oil penetration, which is consistent with the findings reported by Zhang et al. [13,15].

Regarding protein content, a significant increase was observed in both cultivars as the treatment frequency increased. This increase does not imply the synthesis of new proteins, but reflects a higher relative concentration attributable to the reduction in fat and moisture during frying. In addition, ultrasound is known to induce mechanical effects through cavitation that alter the cellular microstructure, facilitating the rupture of cell walls and the exposure of intracellular proteins, which improves their extraction and detectability in chemical analyses [38,39]. Therefore, ultrasound treatment may have favored protein accessibility, facilitating their quantification by the Kjeldahl method.

The carbohydrate content remained relatively stable between treatments, with statistical differences of low magnitude that do not represent a relevant change at the nutritional level. However, specific fractions such as reducing sugars showed a significant decrease with ultrasound, which can be attributed to cavitation effects that favor the extraction or degradation of these soluble compounds into the interstitial medium [40,41]. This characteristic is technologically relevant, as it contributes to reducing the formation of acrylamide and improving the sensory quality of the final snack. About moisture, no significant differences were observed between the treatments. This result suggests that the effect of ultrasound did not alter the final moisture content, which can be explained by the equilibrium reached during the thermal process, where the final product reaches low and stable moisture levels (<3%) characteristic of crispy snacks [5,42]. Finally, the increase in ash content could be attributed to a higher concentration of minerals, a consequence of differential dehydration or the redistribution of solids during heat treatment.

Overall, the results obtained reflect the potential of ultrasound treatment to reduce fat absorption with adequate protein content, without negatively affecting the nutritional structure of the product.

3.4. FTIR Analysis

Figure 1a,b show the IR spectra of the chips from the Sempal and Agustina potato varieties, respectively. In both cases, similar functional groups were observed, indicating consistent patterns in the structural composition after ultrasound treatment. Peaks of 2853 cm⁻¹ and 2855 cm⁻¹ were observed in the chips, which are attributed to the -CH₂ and -CH₃ functional groups present in the fatty acid chains and their asymmetric stretching vibration. In addition, peaks at 1744 cm⁻¹ and 1746 cm⁻¹ were observed, which would be related to the vibration of the carbonyl group and the formation of a complex between amylose and the lipids of the vegetable oil used during frying [5,13]. This effect could be linked to greater cavitation in treatments with higher ultrasound frequencies, which would generate a more porous and cracked structure, facilitating such interactions, as can also be observed in the SEM analysis [5,13]. These changes, induced by the increase in ultrasound frequency, could be related to improvements in the textural and sensory properties of the chips, such as greater crispness and lower oil absorption, which are important aspects in the acceptance of the final product [43].

3.5. SEM Analysis

Prior to microstructural analysis, photographs were taken of the fried chips corresponding to the Sempal and Agustina varieties. Figure 2a–f clearly show the changes induced by ultrasound treatment, revealing greater roughness, surface undulations, bubble collapse, and more irregular morphological patterns. These visual modifications suggest a structural alteration attributable to the effects of acoustic cavitation. These initial observations support the expected physical effects of ultrasound and were subsequently analyzed in greater detail using scanning electron microscopy.

SEM analysis revealed the effects of ultrasound treatment on the surface microstructure of fried chips. In the control samples (Figure 3a,b), corresponding to the Sempal and Agustina varieties, a continuous, relatively smooth and compact structure was observed, with few pores or cavities, characteristic of tissues with high oil retention during frying. In contrast, the chips treated at 28 kHz (Figure 3c,d) showed initial signs of structural disruption, such as microcracks, partial separation of the tissue, and localized expansion, suggesting an effect of ultrasonic cavitation on the cellular matrix. Finally, the most notable change was recorded in the micrographs obtained after treatment at 40 kHz (Figure 3e,f), where a more porous microstructure was observed, with defined channels and homogeneously distributed cavities. This increased porosity can be attributed to the intensified mechanical effects of acoustic cavitation at higher frequencies. These effects induce the formation and collapse of microbubbles, which in turn generate localized disruptions in cell walls and the intercellular matrix [13,15].

The structural modifications induced by ultrasound, especially at 40 kHz, favor greater porosity in the matrix of the fried chips, which facilitates moisture evaporation during frying and reduces oil absorption, as shown by the physicochemical results obtained and by previous studies on chips previously treated with ultrasound [13,15]. This increased porosity also contributes to the development of a lighter and airier texture. These sensory attributes are positively valued by consumers of this type of product [5], as evidenced in the sensory evaluation described in the following section. Together, these findings reinforce the hypothesis that ultrasonic treatment not only favors the microstructure of the product but also improves its technological and sensory quality.

3.6. Sensory Evaluation

In the preference test, the sample treated with ultrasound at 40 kHz was the most highly rated in both varieties: Sempal (55%) and Agustina (40%), as shown in Figure 4a,c. In the hedonic evaluation, the Kolmogorov–Smirnov test indicated a lack of normality, so the Friedman test was applied to compare the mean acceptance ranks. In both varieties, the sample treated with 40 kHz obtained the highest scores for texture and flavor (Figure 4b,d). These results are attributed to the ultrasound-induced modifications in the microstructure of the tissue, also observed in the SEM analysis, which showed greater porosity and improved crispness. This more open structure favors moisture evaporation during frying and limits oil absorption, which directly contributes to a crispier and lighter texture, characteristics appreciated by consumers [13,15]. Likewise, the reduction in fat and sugar content, confirmed in physicochemical analyses, contributed to a reduced fat content and a more pleasant texture. These changes not only improve the nutritional profile of the product but also increase its sensory acceptance by minimizing unwanted flavors and colors associated with the Maillard reaction [5,41]. Overall, the sensory results confirm that treatment with 40 kHz ultrasound significantly improves the organoleptic quality of fried chips, establishing itself as an effective technological alternative for the revaluation of native potatoes in the snack industry. However, it should be noted that the panel consisted solely of untrained individuals between the ages of 20 and 30, which may limit the generalizability of the sensory results; therefore, future studies should include trained panels and/or a broader demographic representation.

4. Conclusions

Ultrasound treatment prior to frying produced different effects depending on the frequency applied, with 40 kHz being the most effective condition for improving the characteristics of native potato chips. This treatment promoted the development of a more porous microstructure, reduced oil absorption from 33.49% to 33.14% in Sempal and from 22.84% to 22.07% in Agustina. In addition, key sensory attributes such as flavor and texture were improved. Morphological characterization revealed evident alterations induced by cavitation, while physicochemical and sensory analyses confirmed substantial improvements in product quality and acceptance. The combined effects of ultrasound on the tissue matrix and its impact on functional attributes reinforce its potential as a sustainable and applicable technology in the processing of snacks based on Andean crops. These findings open new opportunities for the agro-industrial valorization of native varieties, proposing a technological alternative with benefits such as greater consumer acceptance and satisfaction due to improved texture and lower fat content, and advantages for producers by enabling a higher-quality, value-added product with greater commercial opportunities. However, it should be noted that the limited frequency range and the fixed treatment time used in this study represent constraints that may limit the extrapolation of the results; therefore, future research should explore a broader range of ultrasonic parameters to optimize processing conditions. In addition, it is recommended to incorporate analyses such as Thiobarbituric Acid Reactive Substances (TBARS) and Peroxide Value (POV) to evaluate oxidative stability, which could further strengthen the product development perspective.