Valorization of Andean Native Potatoes Through Chuño Processing: Effects of Potato Variety and Freezing Temperature on Physicochemical, Bioactive, Nutritional, and Technological Properties

Abstract

Chuño is a traditional Andean product obtained by freezing, thawing, and drying potatoes. This study aimed to assess how different Andean potato varieties (Chihuanki Negro [C], Puka Huayro Machu [P], and Yana Huayro Machu [Y]) and freezing temperatures (−10 °C, −20 °C, and −30 °C) modulate the physicochemical (pH, acidity, and moisture), bioactive (phenolics and antioxidant activity), nutritional (proximate composition and minerals), and techno-functional (water absorption and swelling power) attributes of chuño. The results revealed that variety C retained higher macronutrient levels at 10 °C, featuring higher carbohydrates, proteins, and minerals (e.g., magnesium and zinc), while P showed enhanced fiber and mineral retention, alongside a faster rehydration and antioxidant capacity, particularly at −20 °C and −30 °C. Color differences were also noted, with P presenting reddish tones and a higher luminosity, whereas C had a more intense yellow hue linked to carotenoids. In general, −10 °C and −20 °C better preserved antioxidant compounds than −30 °C. These findings underscore how the proper selection of potato variety and freezing temperature can optimize the nutritional, functional, and sensory characteristics of chuño. However, these outcomes stem from selected samples, suggesting that further research is needed to confirm the broader applicability of the proposed method across additional varieties and process conditions.

1. Introduction

Malnutrition and food insecurity remain pressing challenges in many rural regions worldwide, especially in countries with extensive agrobiodiversity, such as Peru [1]. Despite the abundance of native crops—many of which have considerable nutritional and cultural value—the limited scientific knowledge about their properties constrains their use. In this context, traditional products like chuño may offer a valuable food resource to enhance food security and nutrition for vulnerable populations, directly contributing to the United Nations Sustainable Development Goals (SDGs), particularly SDG 2 (Zero Hunger) and SDG 3 (Good Health and Well-Being) [2].

Chuño is an ancestral food typical of the Andean region, produced by subjecting potatoes to repeated cycles of freezing and dehydration. This technique exploits the low nocturnal temperatures and intense daytime solar radiation in high Andean zones to dehydrate the tuber and significantly extend its shelf life, thereby strengthening the food resilience of rural communities [3,4]. Various studies indicate that chuño retains most of its carbohydrates, proteins, and essential micronutrients, making it a stable and nutritious food [5]. Moreover, its significant content of resistant starch, polyphenols, and antioxidants can support intestinal health, regulate blood glucose, and help prevent chronic diseases—benefits that largely persist after dehydration [6,7].

From a nutritional perspective, chuño stands out for its complex carbohydrates—an ideal energy source for high-demand physical activities—and for containing plant-based proteins that complement an Andean diet primarily based on cereals and legumes [1,8,9]. Its low-fat content makes it suitable for dietary plans that focus on controlling lipid intake, whereas the fiber remaining after dehydration supports digestive health and cholesterol regulation [10,11,12]. Additionally, relevant levels of minerals, such as calcium, iron, potassium, and phosphorus, have been reported to be crucial for muscle function and bone formation [13,14].

Despite these multiple benefits, a gap remains regarding the impact of specific processing variables—particularly freezing temperature—impact the nutritional and functional properties of chuño [15,16]. In Peru, the numerous native potato varieties exhibit important differences in resistant starch composition, polyphenol profiles, and mineral content, suggesting that freeze–thaw cycles may affect the final quality of the product depending on the variety used [1,17]. Moreover, chuño not only has cultural significance but is also produced sustainably through simple local technologies that capitalize on the climatic conditions of the Andean highlands [18].

Accordingly, this study aimed to simultaneously evaluate the effect of two key variables—the potato variety (Chihuanki Negro, Yana Huayro Machu, and Puka Huayro Machu) and the freezing temperature—on the elaboration of chuño. These three native varieties were chosen based on their distinct pigmentation (ranging from yellow to red to dark purple), cultural relevance in the Andean region, and contrasting physicochemical profiles—particularly regarding starch composition and polyphenol content—which may lead to different responses under freeze–thaw processing. Physicochemical, bioactive, nutritional, and techno-functional properties were analyzed to determine how these factors influence the overall quality of the final product. The results will provide practical recommendations for the sustainable valorization of native potato varieties through chuño production, thereby contributing to food security, cultural heritage, and the nutritional potential of this product at both local and global levels.

2. Materials and Methods

2.1. Raw Material

This study used three native Peruvian potato varieties (Figure 1), chosen for their cultural significance and local availability in the Tarma region, located in the central Andean highlands of Peru. The varieties were as follows: Yana Huayro Machu (Y), also known as Huayro macho negro or Huayro negro; Puka Huayro Machu (P), called Huayro macho rojo or pepino rojo; and Yana Chihuanki (C), identified as Chihuanki negro or Yana Tarma. Potatoes were cultivated in the Acobamba district (12°50′27″ S, 74°34′14″ W) at an altitude of 3048 masl during the June–July (winter) 2024 planting season. Healthy, uniformly sized, and mature tubers were selected for each variety, obtaining 3 kg of raw material per variety for subsequent tests.

2.2. Experimental Design

A completely randomized block design (CRBD) was used to evaluate the effects of potato variety and freezing temperature on chuño properties. Two factors were considered: potato variety (Y, P, and C) and freezing temperature (−10 °C, −20 °C, and −30 °C). Each combination was analyzed in triplicate, resulting in nine independent experiments. The experimental coding scheme is presented in

Table 1. Experimental coding based on potato variety and freezing temperature.

Potato Variety	Freezing Temperature (°C)
	−10	−20	−30
Puka Huayro Machu	P(−10)	P(−20)	P(−30)
Yana Chihuanki	C(−10)	C(−20)	C(−30)
Yana Huayro Machu	Y(−10)	Y(−20)	Y(−30)

.

2.3. Chuño Production Process

Figure 2 outlines the chuño production process. The potatoes were previously washed under running water for 20 min and frozen in an ultrafreezer (CCF/L-150, CIMMSA, Lima, Peru) at the designated temperatures listed in Table 1 (−10 °C, −20 °C, and −30 °C) for 24 h. Freezing ended once the tubers reached an internal temperature below −10 °C, measured using a calibrated digital probe thermometer inserted into the geometric center of the tubers. They were then thawed in metal containers filled with water at approximately 20 °C for 2 h and gently rubbed to remove any remaining peel. Next, the tubers were soaked for 24 h at a ratio of 1 kg of potatoes per 5 L of water to homogenize moisture and facilitate the removal of soluble compounds. The samples were then sliced into discs roughly 2 mm thick and dehydrated in a forced-air dryer (LT102, Vulcano, Santiago, Chile) at 40 °C for 48 h. Once dried, the product was processed with a disintegrator mill (MPD-102, Biobase Biodustry, Jinan, China) and sieved with a 1 mm mesh to obtain fine chuño flour. Finally, these flours were vacuum-packed into portions of approximately 100 g each for further analysis.

2.4. Evaluation of the Physicochemical and Bioactive Characteristics of Chuño Obtained from Different Potato Varieties and Freezing Temperatures

2.4.1. Physicochemical Characterization

pH was measured following AOAC 943.02 [19] by preparing a suspension of 10 g of chuño flour in 100 mL of distilled water; this mixture was stirred for 30 min and filtered before being read with a pH meter (Starter 3100, Ohaus Corporation, Parsippany, NJ, USA). The titrated acidity was determined in line with that of AOAC 942.15 [19] by titrating the same suspension with 0.1 N NaOH and expressing the results as citric acid percentage. Moisture content was measured according to AOAC 950.46 [19] by drying approximately 5 g of sample at 105 °C for 5 h in an oven (DHG-9030A, Faithful Instrument Co., Ltd., Ningbo, China) and quantifying weight loss.

2.4.2. Total Phenolic Compounds

Total phenolic compounds (TPCs) were determined using the Folin–Ciocalteu reagent, following the method described by [20]. In brief, a calibration curve was prepared using gallic acid (0.1 mg/mL) at different dilutions. Then, 250 µL of Folin–Ciocalteu reagent were mixed with each calibration standard, followed by 750 µL of 20% sodium carbonate. For the samples, a 0.5 mL aliquot of the methanolic extract (obtained after 2 h of agitation) was combined with 0.25 mL of Folin–Ciocalteu reagent (1 N) and 0.75 mL of 20% sodium carbonate. After resting for 30 min, absorbance was measured using a spectrophotometer (Genesis 30, Thermo Fisher Scientific Inc., Waltham, MA, USA), and the readings were compared with the standard curve to calculate TPCs as gallic acid equivalents.

2.4.3. Antioxidant Capacity

The results were determined using the modified method of [21], employing a DPPH radical (2,2-diphenyl-1-picrylhydrazyl) dissolved in 80% methanol at 150 µM (or 150 mM, depending on unit adjustments). A Trolox standard curve (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid) was also prepared at various concentrations. After the methanolic extraction of the sample for 2 h in darkness and filtration, 0.2 mL of the extract was added to 2.0 mL of DPPH solution. The mixture was vortexed and allowed to rest for 30 min, after which its absorbance was measured using a spectrophotometer (Genesis 30, Thermo Fisher Scientific Inc., Waltham, MA, USA). The percentage of inhibition was calculated and compared with the Trolox curve.

2.5. Nutritional and Techno-Functional Characterization of Selected Chuño Experiments

Based on earlier results, experiments with the highest antioxidant capacity were selected for a more detailed nutritional and techno-functional characterization.

2.5.1. Proximate Composition

Proximate composition was determined using the following AOAC [19] methodologies: ash (923.03) by incineration at 600 °C, fat (923.03) extracted using Soxhlet extractor (VHM-6R, Daihan Scientific Co., Ltd., Seoul, Republic of Korea), crude fiber (962.09) by acid–base digestion, and protein (984.13) by the Kjeldahl digestion unit (KLG-100071, Daihan Scientific Co., Ltd., Seoul, Republic of Korea). Moisture was measured again according to AOAC 950.46, and carbohydrates were estimated by difference [19].

2.5.2. Amylose and Amylopectin Content

Amylose and amylopectin contents were determined following ISO (1987), adapted by [22]. Stock solutions of purified amylose and amylopectin were prepared to construct the calibration curve. One hundred milligrams of each component were weighed into 100 mL volumetric flasks, and then 1 mL of 95% ethanol and 9 mL of 1 N NaOH were added; the solutions stood at room temperature for 18–24 h before being topped up to 100 mL with distilled water. For the sample, the chuño flour was first dried (12 h at 50 °C). Then, 1 mL of 95% ethanol and 9 mL of 1 N NaOH were added; after 18–24 h of resting, the volume was brought to 100 mL with distilled water. One milliliter of this solution was then mixed with 1 mL of 1 N acetic acid and 2 mL of 2% iodine. After 20 min in the dark, absorbance was measured at 620 nm (Genesis 30, Thermo Fisher Scientific Inc., Waltham, MA, USA). The amylose percentage was calculated based on the calibration curve, and amylopectin was obtained by subtracting the amylose percentage from 100.

2.5.3. Mineral Quantification

Mineral analysis followed EPA methods 3050B Revision 2 (1996) and 6010D Revision 5 (2018), involving acid digestion and determination by ICP-OES system (Optima 8000, PerkinElmer Inc., Waltham, MA, USA) [23]. For this purpose, 0.5 g of chuño flour was weighed into a digestion flask, followed by controlled addition of nitric, perchloric, and hydrochloric acids to ensure total element dissolution. After digestion, the solution was filtered, diluted with ultrapure water, and introduced to the ICP-OES, which was previously calibrated with 1, 5, 10, and 20 mg/L standards. The optical emission wavelengths of each mineral were measured and compared with the calibration curve.

2.5.4. Techno-Functional Characteristics

Instrumental color was measured in the CIELab system (L*, a*, b*) using a portable colorimeter (CR-400, Konica Minolta, Tokyo, Japan), with triplicate measurements. The water absorption index (WAI), water solubility index (WSI), and swelling power (SP) were determined as described in [24]. Briefly, 0.5 g of the sample was suspended in 6 mL of distilled water at 30 °C and homogenized in a water bath (WB-22, Daihan Scientific Co., Ltd., Seoul, Republic of Korea) for 30 min. The mixture was then centrifuged at 5000 rpm for 20 min and filtered. Two milliliters of the filtrate were dried in an oven (DHG-9030A, Faithful Instrument Co., Ltd., Ningbo, China) at 90 °C for 4 h, after which the weights of both the sedimented gel and the dried supernatant were recorded. These values were used to calculate WAI, WSI, and SP, providing insights into the behavior of chuño flours in applications requiring water absorption, solubility, or expansion.

2.6. Statistical Analysis

All tests were performed in triplicate, and results are expressed as mean ± standard deviation. The effects of potato variety and freezing temperature were analyzed using ANOVA. When statistically significant differences were identified (p < 0.05), Tukey’s test was applied for mean comparisons. Additionally, the best-performing treatments were subjected to principal component analysis (PCA) to identify multivariate correlations and interactions among the studied variables. Statistical processing was performed using the designated software (Python, 3.13.1, 2024).

3. Results

3.1. Physicochemical and Bioactive Characteristics of Chuño Obtained from Different Potato Varieties and Freezing Temperatures

Figure 3a–c shows how the potato variety (P, C, and Y) and freezing temperature (−10 °C, −20 °C, and −30 °C) influenced the physicochemical properties of the resulting chuño. According to the statistical analysis (

Table 2. Analysis of variance (ANOVA) for the physicochemical and bioactive characteristics of potato-based chuño, considering variety (P, C, and Y) and freezing temperature (−10 °C, −20 °C, and −30 °C).

Characteristic		sum_sq	df	F	PR (>F)	Interpretation 1
pH	Block	0.01098	1	3.367793	0.072683	NS
	Variety	1.235915	2	189.5467	1.65 × 10−23	S
	Temperature	0.102959	2	15.7904	5.38 × 10−6	S
	Residual	0.156489	48
Acidity	Block	0.011374	1	0.674253	0.415632	NS
	Variety	0.708038	2	20.98633	2.83 × 10−7	S
	Temperature	0.483072	2	14.31833	1.33 × 10−5	S
	Residual	0.809713	48
Moisture	Block	2.925304	1	0.563877	0.456368	NS
	Variety	8.24633	2	0.794775	0.457537	NS
	Temperature	465.6147	2	44.87557	1.03 × 10−11	S
	Residual	249.0164	48
Total Phenolics Compounds	Block	1.97 × 10−6	1	0.254889	0.615964	NS
	Variety	0.000543	2	35.16157	3.95 × 10−10	S
	Temperature	0.000283	2	18.28835	1.25 × 10−6	S
	Residual	0.000371	48
Antioxidant Capacity (% inhib.)	Block	12.91063	1	1.688428	0.200015	NS
	Variety	33.89291	2	2.216226	0.120057	NS
	Temperature	71.44007	2	4.6714	0.014005	S
	Residual	367.0338	48
Antioxidant Capacity (mmET)	Block	0.068892	1	3.837632	0.055937	NS
	Variety	0.03043	2	0.847557	0.434772	NS
	Temperature	0.152907	2	4.258812	0.019832	S
	Residual	0.861687	48

¹ S = statistically significant differences (p < 0.05), NS = no statistically significant differences.

), both factors significantly affected pH and titratable acidity (p < 0.0001), whereas moisture was primarily influenced by temperature (p = 1.03 × 10⁻¹¹) and not by variety (p = 0.4575).

C exhibited the highest pH, exceeding 6.6 regardless of temperature. Meanwhile, variety P remained around 6.3–6.4 when frozen at −10 °C, slightly decreasing at lower temperatures. Y exhibited the greatest pH fluctuation, consistent with its susceptibility to chemical changes following freezing. Regarding titratable acidity, Y showed higher values at −20 °C, exceeding 1% in some trials, while P and C ranged between 0.6–1.0% and 0.7–0.9%, respectively, depending on temperature.

For moisture, −10 °C yielded generally moderate percentages (5–8 g/100 g in C and Y, up to 13 g/100 g in P), whereas, at −30 °C, values tended to be higher—surpassing 12% in some instances—likely reflecting how freeze–thaw dynamics affect water retention after drying.

In the bioactive assessment (Figure 4), which measured the TPCs (Figure 4a) and antioxidant capacity (via DPPH) (Figure 4b), the ANOVA (Table 2) revealed strong effects from both variety (p < 0.0001) and temperature (p < 0.0001) on TPCs, whereas antioxidant capacity (% inhibition) depended mainly on temperature (p = 0.0140 and p = 0.0198, respectively) and showed no clear statistical influence from variety.

Variety C had the highest phenolic concentration, reaching up to 0.020 mg/100 g at −10 °C and −20 °C, P was intermediate (0.007–0.010 mg/100 g), and Y registered the lowest levels (~0.004–0.006 mg/100 g). The antioxidant capacity was the highest in samples frozen at −10 °C and −20 °C (about 38–40% inhibition in P and C, and 35–36% in Y). At −30 °C, inhibition generally decreased, suggesting the possible degradation or reduced preservation of antioxidant compounds at lower temperatures.

Overall, these findings indicate that potato variety strongly influences pH, acidity, and TPCs, whereas freezing temperature significantly affects moisture and antioxidant capacity. Controlling freezing conditions and selecting an appropriate variety are thus key strategies for optimizing the physicochemical and bioactive characteristics of this traditional Andean product.

3.2. Nutritional and Techno-Functional Characteristics of Selected Chuño Samples

Based on earlier results, chuño samples P(−20), P(−30), C(−10), and C(−20) were chosen for a more detailed evaluation of their nutritional and techno-functional properties, as they exhibited the highest antioxidant capacity (Figure 4b.

Table 3. Nutritional and techno-functional characteristics of selected potato-base chuño samples ¹.

Characteristics	P(−20)	P(−30)	C(−10)	C(−20)
Proximate composition
Carbohydrates	83.10 ± 0.28 b	81.37 ± 0.10 c	89.19 ± 0.04 a	84.97 ± 0.06 b
Fiber	0.98 ± 0.04	1.04 ± 0.06	0.90 ± 0.01	1.00 ± 0.06
Protein	3.14 ± 0.08 b	3.00 ± 0.11 b	3.26 ± 0.05 b	4.06 ± 0.00 a
Fat	0.18 ± 0.00 c	0.25 ± 0.01 b	0.31 ± 0.01 a	0.12 ± 0.01 d
Ash	2.13 ± 0.08 b	2.33 ± 0.07 a	1.66 ± 0.11 c	1.96 ± 0.08 b
Moisture	4.45 ± 0.23 b	12.00 ± 0.02 a	4.67 ± 0.11 c	7.89 ± 0.09 b
Amylose	13.87 ± 0.06 b	13.16 ± 0.07 c	14.24 ± 0.03 b	15.63 ± 0.03 a
Amylopectin	86.12 ± 0.06 a	86.83 ± 0.07 a	85.75 ± 0.03 b	84.36 ± 0.03 c
Minerals
Ca	752.00 ± 0.01 b	723.80 ± 0.01 c	793.30 ± 0.01 a	688.90 ± 0.01 d
Fe	24.26 ± 0.07 b	25.35 ± 0.07 b	22.99 ± 0.07 c	25.83 ± 0.07 a
K	6698.00 ± 0.06 b	6785.00 ± 0.06 a	5887.00 ± 0.06 c	5919.00 ± 0.06 c
Mg	532.50 ± 0.03 c	536.40 ± 0.03 b	572.70 ± 0.03 a	574.00 ± 0.03 a
Mn	6.81 ± 0.01 b	6.82 ± 0.01 b	7.66 ± 0.01 a	7.68 ± 0.01 a
Na	81.24 ± 0.01 b	84.66 ± 0.01 a	76.61 ± 0.01 c	80.27 ± 0.01 b
Zn	14.02 ± 0.07 c	15.95 ± 0.07 b	17.50 ± 0.07 a	18.98 ± 0.07 a
Instrumental color
a*	14.42 ± 0.12 a	14.30 ± 0.12 a	7.53 ± 0.02 b	7.65 ± 0.03 b
b*	20.40 ± 0.15 b	21.50 ± 0.15 b	29.60 ± 0.02 a	30.08 ± 0.01 a
L*	98.01 ± 0.10 a	99.11 ± 0.10 a	88.72 ± 0.05 b	87.38 ± 0.02 b
WAI	3.55 ± 0.10 a	3.34 ± 0.10 ab	3.29 ± 0.03 ab	2.88 ± 0.08 b
WSI	1.65 ± 0.25 b	1.44 ± 0.25 b	2.85 ± 0.08 a	3.07 ± 0.45 a
SP	3.59 ± 0.10 a	3.38 ± 0.10 ab	3.39 ± 0.02 ab	2.97 ± 0.10 b

¹ Values represent mean ± standard deviation (n = 3). Superscript letters indicate significant differences (p < 0.05) by Tukey’s test.

presents the proximate composition, amylose content, mineral content, and techno-functional properties of the four selected experiments. ANOVA confirmed statistically significant differences (p < 0.05) for most variables, except crude fiber, which showed no relevant changes (

Table 4. Analysis of variance (ANOVA) for the nutritional and techno-functional characteristics of selected potato-based chuño samples.

Characteristic	sum_sq	F	PR (>F)	Interpretation 1
Proximate composition
Moisture	114.6167	1957.124	8.43 × 10−12	S
Ash	0.710347	27.61945	0.000143	S
Fiber	0.033052	3.867249	0.055968	NS
Fat	0.063882	80.49628	2.57 × 10−6	S
Protein	2.031822	109.175	7.88 × 10−7	S
Carbohydrates	133.7584	1817.388	1.13 × 10−11	S
Amylose	9.676322	913.55	1.76 × 10−10	S
Amylopectin	9.676322	913.55	1.76 × 10−10	S
Minerals
Ca	17,547.35	39,744,838	4.99 × 10−29	S
Fe	14.35513	757.6866	3.72 × 10−10	S
K	2,121,232	1.53 × 108	2.26 × 10−31	S
Mg	4574.59	1,212,856	5.75 × 10−23	S
Mn	2.19927	3875.365	5.5 × 10−13	S
Na	98.78711	140,522.2	3.19 × 10−19	S
Zn	40.61586	2465.265	3.35 × 10−12	S
Instrumental color
L*	335.6518	16,554.96	1.66 × 10−15	S
a*	137.9484	5468.718	1.39 × 10−13	S
b*	238.9951	6794.459	5.83 × 10−14	S
WAI	0.707921	30.16247	0.000104	S
WSI	6.178886	23.66564	0.000248	S
SP	0.621524	25.40515	0.000193	S

¹ S indicates statistically significant differences (p < 0.05), whereas NS indicates no statistically significant differences.

).

The proximate composition showed a significantly higher carbohydrate content in sample C(−10) (92.19%) than in the other conditions. The protein content reached its highest level in C(−20) (4.06%), exceeding P(−20), P(−30), and C(−10) (2.99–3.26%). Differences in fat content were also notable: C(−10) had the highest value (0.31%), while C(−20) had the lowest (0.12%). Regarding moisture content, P(−30) retained the largest amount of water (10%), whereas C(−10) exhibited the smallest moisture content (1.67%). Regarding the starch fractions, C(−20) had the highest amylose content (15.63%) and, consequently, the lowest amylopectin level (84.36%), whereas P(−30) had the lowest amylose (13.16%) and the highest amylopectin (86.83%).

Mineral analysis showed calcium (Ca) to be the most abundant in C(−10) (793.3 mg/kg), while iron (Fe) peaked in C(−20) (25.83 mg/kg). Potassium (K) was the highest in P(−30) (6785 mg/kg), and variety C displayed elevated magnesium (Mg) and manganese (Mn) levels under both −10 °C and −20 °C conditions. Zinc (Zn) increased markedly in C(−10) and C(−20) (17.50–18.98 mg/kg), surpassing P(−20) and P(−30).

Color measurements (CIELab) revealed that P samples maintained a* values above 14, indicating more pronounced reddish hues, while C(−10) and C(−20) hovered around 7.5–7.6. In the b* parameter, C had values above 29.6—yielding a more yellowish tone—whereas P flours remained around 20.4–21.5. Lightness (L*) was significantly higher for P (98–99) than for C (87–88), confirming the presence of brighter flours in P and darker flours in C.

Regarding water-related properties, statistically significant differences (p < 0.05) were found in WAI and SP. Sample P(−20) exhibited the highest values for WAI (3.55) and SP (3.59), followed by P(−30) and C(−10), whereas C(−20) showed the lowest values (2.88 and 2.97, respectively). These results indicate superior water retention and swelling capacity in P(−20), which may be attributed to its higher amylopectin content and more open starch structure. In contrast, WSI tended to be higher in C(−10) and C(−20) (2.85–3.07) compared to P(−20) and P(−30) (1.44–1.65), suggesting a more soluble and fragmented matrix in the former samples.

3.3. Multivariate Analysis of Pearson Correlations and Principal Component Patterns (PCA)

Figure 5 presents a multivariate analysis, including the Pearson correlation matrix and principal component analysis (PCA), performed on the selected chuño samples (P(−20), P(−30), C(−10), and C(−20)).

In Figure 5a, the Pearson correlation matrix shows strong positive correlations (r ≥ 0.90) among minerals such as potassium (K) and magnesium (Mg). Additionally, moderate positive correlations were observed between WSI and color parameters b* and L*. A perfect negative correlation was observed between amylose and amylopectin (r = −1.00), while a moderately strong negative correlation (r = −0.66) was noted between the moisture and carbohydrate content, indicating that higher moisture is associated with a lower carbohydrate concentration in the flours.

Figure 5b displays the PCA loadings plot (PC1 vs. PC2), showing the contribution of each variable to the first two principal components. PC1 was mainly influenced by moisture, fat, iron, calcium, and ash, while PC2 was primarily affected by zinc, protein, carbohydrates, and amylopectin. In contrast, variables such as amylose and fiber contributed negatively to PC2. The spatial orientation of techno-functional properties such as WAI, SP, and WSI suggests that these traits contribute distinctively to sample variability, although they are less aligned with the nutritional axes. The eigenvector values for each principal component are detailed in Supplementary Table S1.

These results indicate that variability in the selected chuño samples is largely explained by differences in mineral composition, carbohydrate content, water–flour interaction properties, and starch composition (amylose vs. amylopectin). The strong association among certain variables suggests that characteristics such as mineral composition and the techno-functional profile could serve as useful predictors to differentiate and select varieties and optimal processing conditions for producing chuño with specific, desirable attributes.

4. Discussion

4.1. Effects of Potato Variety and Freezing Temperature on Chuño Characteristics

The physicochemical properties (pH, acidity, and moisture) and antioxidant capacity of chuño significantly varied when processed using different potato varieties and freezing temperatures. These differences are largely due to each potato variety’s distinct freezing point [2], which influences crystal formation and enzymatic activity during freezing and thawing.

The variety Chihuanki Negro (C) exhibited marked pH stability at −10 °C and −30 °C, suggesting the reduced susceptibility to enzymatic or chemical changes. This resilience may be linked to the presence of phenolic compounds and organic acids that buffer pH fluctuations [25]. Previous studies have noted that varieties with high polyphenol levels slow oxidative degradation and lessen the hydrolysis of natural acids [26]. At −10 °C and −30 °C, enzymatic activity (especially related to the hydrolysis of acidifying compounds) can decrease sharply [27], explaining the pH stability in C.

On the other hand, Yana Huayro Machu (Y) showed a substantial acidity increase at −20 °C, possibly stemming from the partial carbohydrate degradation that generates organic acids [28,29]. While this might be beneficial for preservation—given that more acidic conditions inhibit microbial growth—it can also affect flavor and texture [30]. The genetic diversity among varieties entails differences in starch structure and phenolic compound concentrations, factors that modulate changes in pH and acidity [31]. Thus, while C may be optimal for products requiring physicochemical stability, Y—with a higher sensitivity to temperature—may demand stricter process controls.

The chuño moisture content depends on potato variety and, above all, freezing temperature. According to the data, Y and C had higher moisture at −30 °C, consistent with the formation of smaller ice crystals at very low temperatures. This phenomenon helps to preserve the cellular structure and reduces water loss during thawing [32,33]. Although variety did not significantly affect moisture from a statistical standpoint, the crystal-formation dynamics partly depend on tuber composition—like the amylose/amylopectin ratio and fiber and protein content [34].

Storage at −30 °C not only minimizes sublimation-driven dehydration but also lowers enzymatic activity, reducing cell wall rupture [35,36]. In the food industry, achieving a high moisture retention in chuño is desirable in order to maintain juiciness and avoid excessive weight loss, a crucial aspect for products intended for prolonged freezing [37]. However, at intermediate temperatures such as −20 °C, ice formation and recrystallization of varying sizes may occur, leading to greater liquid exudation upon thawing, especially in more susceptible varieties.

During chuño production, a mild to moderate loss of phenolic compounds, pigments, and antioxidants occurs, similar to what has been observed in chuño produced from Bolivian potatoes [38]. The freeze–thaw process can disrupt cell vacuoles and release polyphenol oxidase, facilitating phenolic compound oxidation [38]. Nevertheless, our findings indicate that the Puka Huayro Machu (P) variety better preserved its antioxidant capacity when frozen at −10 °C and −20 °C, presumably due to the reduced flavonoid and secondary metabolite degradation under moderate thermal ranges [39,40].

Overall, extremely low temperatures like −30 °C may provide enhanced cellular integrity [15], but if the thawing and drying steps are not optimized, they can favor oxidative enzyme release and the subsequent degradation of antioxidant compounds. In fact, variety P retained a higher antioxidant capacity at −10 °C and −20 °C, whereas Chihuanki Negro (C) also performed better at −10 °C and −20 °C in terms of free radical inhibition and phenolic content. These results suggest that each species exhibits a distinct sensitivity to temperature ranges and freezing-related stress.

Multiple studies have emphasized that the presence of polyphenols, flavonoids, anthocyanins, and carotenoids endows tubers with antioxidant properties and pharmacological potential, offering protection against oxidative stress and various cardiovascular diseases [15,38]. Thus, variety selection and freezing-temperature control affect not only the sensory quality but also the functional and nutraceutical value of chuño.

These results highlight the importance of carefully selecting the potato variety and freezing parameters to optimize the physicochemical and bioactive properties of chuño. A variety such as C, which maintains a stable pH and acidity, can achieve a longer shelf life and fewer chemical alterations, whereas P shows an improved retention of antioxidant compounds at intermediate temperatures, making it suitable for nutraceutical-oriented applications. Additionally, the higher moisture retention observed in Y and C at −30 °C indicates that more extreme freezing can promote a juicier texture—an aspect crucial for consumer acceptance [31].

It is worth noting that chuño processing, even under optimal conditions, involves certain losses of bioactive compounds and minerals [38]. Future research could explore pre-treatment methods (e.g., enzymatic inactivation, and the application of natural antioxidants) or milder drying technologies to minimize the degradation of phenolics and maintain the product functionality. Likewise, further investigation into the interplay among freezing temperature, the drying rate, and each potato variety’s specific composition would help develop processing protocols tailored to the concrete objectives of preservation, sensory quality, and nutritional benefits.

4.2. Nutritional and Techno-Functional Potential of Andean Peruvian Potato Chuño

Carbohydrate, protein, and fat contents were noticeably higher in various forms of C processed at −10 °C, suggesting that moderate thermal conditions impede macronutrient degradation. This diminished degradation may stem from the reduced protein denaturation and less intense starch retrogradation, thereby preserving the tuber cellular and functional integrity [11]. In contrast, variety P showed increased proportions of fiber, ash, and moisture at −20 °C and −30 °C. The capacity of insoluble fibers (e.g., cellulose and hemicellulose) to retain water under extreme freezing yields a final product with elevated moisture and limited mineral loss. Consequently, although C may favor a higher energy and protein supply at moderate temperatures, P stands out for its fiber and mineral content when frozen at lower temperatures.

Regarding mineral profiles, variety C exhibited notable concentrations of magnesium, manganese, and zinc—essential nutrients for enzymatic activity, stable cellular structures, and antioxidant defense [41]. Conversely, P excelled in calcium and potassium, which are vital for cell wall rigidity and osmotic regulation [42]. It is likely that genetic factors, combined with freezing and dehydration processes—especially at extremely low temperatures—affect mineral redistribution [43]. Although decreased water mobility at −30 °C may preserve certain trace elements, it can also modify internal cell structures, generating differences among varieties. Consequently, C is well-suited for formulations requiring antioxidant and metabolic benefits (Mg, Mn, and Zn), whereas P is ideal for products aimed at enhancing cellular integrity and water regulation (Ca and K).

Temperature effects are not limited to nutrient retention. Thermal shifts also alter the cellular morphology, influencing the final moisture content and the capacity to retain key compounds. At −20 °C and −30 °C, ice crystal size and formation rates can vary, potentially causing greater or lesser cell wall rupture. For example, P exhibited a high moisture percentage under these conditions, indicative of a structure able to retain water even after drying and thawing, while C concentrated more of its macronutrients at −10 °C due to the reduced cell disruption. These findings are consistent with studies on how freezing temperatures affect the sensory and nutritional qualities of plant-based products [35].

Chuño color also differed considerably. P, which has reddish hues and a high brightness, appears to benefit from the elevated anthocyanin levels that guard against enzymatic browning [44]. Moreover, lower polyphenol oxidase activity at cold extremes (e.g., −30 °C) or robust cell walls may explain why P retains vivid tones. In contrast, C exhibited a more intense yellow shade and lower brightness, which were linked to the abundant carotenoids [45]. While ultra-low temperatures can preserve certain pigments, extended exposure and thawing may foster enzymatic or non-enzymatic browning and shifting color. Commercially, bright reddish colors are often appealing, whereas deep yellows can reflect a higher antioxidant content.

Functionally, variety P had a higher WAI and SP than C, affirming that it contains a more porous starch with a greater proportion of amylopectin [46]. P’s swelling power (3.593 ± 0.10 at −20 °C and 3.383 ± 0.10 at −30 °C) indicates a pronounced capacity to expand in water, exceeding reference values for cultivars like Pitikiña [17]. This trait makes P suitable for products requiring rapid, substantial hydration, such as purées, soups, or instant foods. Conversely, C showed a lower WAI and SP, suggesting a starch richer in amylose and yielding a more compact, firmer texture upon rehydration. This feature could be advantageous for formulations that require stability and minimal deformation, such as certain baked goods or long-shelf items.

Starch retrogradation—a phenomenon in which amylose and amylopectin realign after gelatinization—becomes especially relevant at lower temperatures [47]. At −30 °C or −20 °C, amylose may coalesce into denser networks, reducing the amylopectin fraction. This matches observations for C, which, due to its higher amylose content, displayed a greater firmness and less gelatinization. Meanwhile, P, which had a higher amylopectin content, retained a swelling capability and water-binding capacity even under extreme cold.

Lastly, correlations among physicochemical parameters (carbohydrate and moisture contents, minerals) and functional properties (WAI and SP) reveal the complexity of chuño production. As amylose increases, amylopectin decreases (inverse relationship), thereby altering water absorption and firmness [48,49]. A higher insoluble fiber level also enhances water retention and cell stability, whereas mineral concentration can affect osmotic equilibrium (sodium and potassium) or stabilize the starch–protein matrix through crosslinking (magnesium and calcium). The positive correlation between moisture and the CIELAB b* coordinate, as described by [50], indicates that retaining more water may intensify the yellow coloration by preserving carotenoids or accelerating enzymatic browning.

It is essential to note that these findings come from chuño samples selected under specific freezing conditions for varieties C and P. Nonetheless, distinct patterns emerge. Variety C, with abundant amylose and higher levels of protein, fat, and minerals such as magnesium and zinc at −10 °C, suits applications requiring firmness and a high caloric density, such as bars, baked products, or functional flours for diabetic-friendly formulations. Meanwhile, variety P, rich in fiber and minerals (calcium and potassium) when processed at −20 °C and −30 °C, is better suited for formulations demanding a higher moisture retention, rapid rehydration, and added nutraceutical value—such as instant soups, porridges, or powdered mixes. Although very low temperatures facilitate fiber and micronutrient conservation, they may also accelerate starch retrogradation or promote cell disruption, whereas −10 °C better preserves protein–energy matrices.

5. Conclusions

Potato variety and freezing temperature exert distinct effects on the physicochemical, bioactive, and techno-functional properties of chuño. The choice of Chihuanki Negro (C) or Puka Huayro Machu (P), alongside the thermal range (−10 °C, −20 °C, and −30 °C), determines the pH stability, titratable acidity, moisture retention, phenolic compound levels, antioxidant capacity, and the macronutrient and mineral profile. Moderate temperatures (−10 °C) generally preserve carbohydrates, proteins, and fats more effectively, while also mitigating starch retrogradation and benefiting the product’s energy concentration and firmness—particularly in variety C. Conversely, lower temperatures (−20 °C and −30 °C) favor fiber and mineral retention in varieties such as P, which also exhibit higher swelling and rehydration capacities.

Moreover, the pH stability in C and sustained antioxidant capacity in P indicate that both varieties offer specific advantages depending on whether the emphasis is on conservation or on nutraceutical value. A principal component analysis revealed that the variability among the selected chuño samples is largely explained by differences in mineral composition, carbohydrate content, water–flour interaction properties, and starch composition (amylose vs. amylopectin). The strong associations among these variables suggest that mineral profiles and techno-functional attributes could serve as useful predictors for selecting suitable potato varieties and optimizing freezing conditions to produce chuño with specific, desirable characteristics. Consequently, selecting the appropriate potato variety and freezing conditions allows for the modulation of the final chuño characteristics, optimizing both texture and functional quality, and opening up possibilities for food developments with industrial as well as nutritional aims.

It is important to note, however, that these findings are based on a limited number of native potato varieties cultivated in a specific region of Peru and tested under controlled laboratory conditions. Furthermore, the study did not evaluate the long-term stability of the final product nor the effects of different drying techniques or storage environments. Future research should address these factors and explore a broader spectrum of native genotypes and processing conditions in order to expand the applicability and industrial scalability of chuño as a functional Andean food.