Drying Hot Red Chilies: A Comparative Study of Solar-Gas-Fired, Tunnel, and Conventional Dryers

Abstract

Drying extends the shelf life of crops; thus, dryers with good designs will help them dry to an optimum level. The present research work was carried out to assess and compare the performance of conventional (CD), solar tunnel (STD), and solar-cum gas-fired dryers (SGD) for drying hot chilies. The Sanam variety of hot chilies was used in this study. Samples were dried using CD, STD, and SGD methods. The drying process was conducted over three days, from 9:00 to 17:00 daily. Results showed significant differences among the drying methods in temperature, relative humidity, and moisture content reduction (p < 0.0001). The SGD consistently outperformed the other methods, achieving the highest temperature (55 °C) and lowest relative humidity (17%), compared to the STD (44 °C, 23%) and CD (34 °C, 31%). The SGD demonstrated superior efficiency, reducing moisture content from 70% to 9.36% in just 36 h, while the STD required 50 h (to 11.37%) and CD took 84 h (to 9.63%). ANOVA and post hoc analyses revealed that the SGD significantly outperformed both the STD (p = 0.0412) and CD (p = 0.0018) in moisture content reduction. Additionally, the SGD and STD better preserved the color of hot chili samples compared to CD, as determined by the Essential Oil Association (EOA) method. It is concluded that the SGD is the most technically suitable method for drying hot chilies, offering improved efficiency and quality retention. It is recommended to use an SGD for optimal results in hot pepper drying.

1. Introduction

The chili (Capsicum annum) is a significant vegetable crop because it is a cheap and plentiful source of fiber, vitamins, and minerals. It has a high ascorbic acid content as well. Chili’s high moisture content causes it to deteriorate quickly after a few days of harvest. Drying is the most popular way of chili preservation, although it uses a lot of energy. The primary goal of drying is to lower the moisture content to a level that permits safe storage for a longer amount of time, hence increasing the shelf life [1].

To reduce the moisture content of agricultural products and extend their shelf life, agricultural products are dried using a traditional method [2,3,4]. By inhibiting the growth of bacteria, yeasts, and molds, this prevents the spoilage of harvested agricultural products. A large number of fruits (50–70%) and grains (10–30%) were reported to be lost because of poor drying and preservation [5]. Good drying of different agricultural products provides a longer shelf life, reduces the weight and volume of the dried products, and thus helps to reduce the costs of packaging and transportation [6,7]. After China, Mexico, and India, Pakistan is the fourth-largest producer of hot chilies. With a yield of 53.7 thousand tonnes, chilies are grown on 38.4 thousand hectares. An average output of 1.7 tonnes per hectare contributes 1.5% of the nation’s GDP [8]. A little town in Pakistan called Kunri used to be recognized as Asia’s chili capital [9]. It is regarded as one of the leading production centers and provides roughly 85% of Pakistan’s production of hot chilies [10]. Dehydration, a critical stage in food preservation, is the elimination of water and moisture to prevent deterioration and improve shelf life. This procedure can be carried out in controlled settings, such as specialist drying equipment, or in direct environmental conditions, where ambient temperature and humidity play an important role. In the area of red chili preservation, numerous approaches have been used on both domestic and industrial sizes to ensure effective dehydration and preservation [11,12]. Due to its quantity and wide distribution on the ground, drying red chilies is a well-known practice in South Asia and is typically carried out in the open sun [13].

In Pakistan, chilies are traditionally sun-dried by the farmer, who usually places the chilies on a mat, an earthen floor, a cement floor, or a metal shed and leaves them there. This traditional drying method lacks control over the process parameters and typically yields a lower quality product. The drying duration is highly dependent on weather conditions, ranging from approximately one to two weeks [14]. This method contaminates chilies with dust, dirt, rainfall, animals, birds, rodent insects, and micro-organisms [15]. The quantity and quality of the product significantly suffer, and losses can be high in these conditions. Many developing countries have 30–40% losses, particularly in Pakistan, about 50% of the total quantity [16,17]. Many dried chilies lose their vibrant color and develop blistering due to the lack of pretreatment before drying. To address this issue, researchers have explored solar drying as a viable alternative [11]. In this study, a pretreatment method of blanching the chilies in hot water (85 °C) for 3 min prior to drying was employed and aimed to potentially improve color retention and reduce blistering during the drying process. Solar dryers have a lesser environmental impact than industrial dryers that use electricity or gas [18]. Mechanical drying is utilized in industrialized nations, but it is difficult for small farms in undeveloped countries due to high investment and operational costs [19].

Solar drying technology is a process that helps agricultural products dry, clean, and save the product so that the product meets national and international levels where the energy cost is zero. Red chilies with a drying capacity of 40 kg were dried using an indirect-force conventional solar dryer, which reduced the moisture content from 80 to 10% (wet basis) in approximately 10 h. In contrast, traditional sun drying required about 65 h to achieve the same moisture reduction. This comparison demonstrates that the solar dryer significantly reduced the drying time by approximately 85% compared to sun drying [20]. Hot chilies with between 12% and 4% (db) moisture content were dried using a forced-circulation indirect solar dryer set to 60 °C [21]. A large-scale greenhouse solar dryer lowered 74% of the moisture content in three days as opposed to open sun drying, which takes five days [22]. When compared to drying in the open sun, using a solar dryer to dry products and medications can significantly cut drying times by up to 40% [23].

Many researchers have chosen solar tunnel and cabinet chili dryers with varying drying efficiencies during the last few decades. In contrast to open sun drying, which takes 85 h to reduce moisture from 73% to 11%, pepper drying takes 36 h to remove moisture from 73% to 10% [24]. According to reports, the overall system efficiency of the solar tunnel chili pepper dryer was 17.63% [25]. In comparison to 124 h under the open sun, chili was dried for about 55 h in a solar tunnel dryer with a 16.25% drying efficiency [26]. In a solar cabinet dryer, Fudholi et al. [27] discovered a 13% drying efficiency for chili peppers. These dryers’ drying capacities are dependent on their size [28].

Therefore, the research was carried out to evaluate the efficiency of the solar-cum gas-fired dryer, solar tunnel dryer, and conventional drying for hot chilies, as well as the temperature and humidity of the solar-cum gas-fired dryer, solar tunnel dryer, and conventional drying.

2. Materials and Methods

2.1. Experimental Procedure

The Sanam hot chili variety was used in the research. After harvesting from the field, the samples were sorted and washed with fresh water. Samples were divided into three groups for the conventional drying (CD) method, solar tunnel dryer (STD), and solar-cum gas-fired dryer (SGD) and replicated three times. Each sample contained 2 kg weight, placed over the tray in a single layer. The size of this variety was approximately 5–8 cm long. To compare the performance of CD, STD, and SGD, one standard tray was kept in each. After the finishing of loading, the drying process began, often beginning at 9:00 and completing at 17:00. The electronic balance was used to assess weight loss, and a hygrometer (testo 175 H1, Helsinki, Finland) was utilized to measure samples’ inner and outside temperatures and relative humidity. A digital solar radiation meter measured the solar radiation during the drying period at 2 h intervals [14].

2.2. Conventional Drying (CD)

The conventional drying method used in this study was traditional sun drying, which is also referred to as open-air drying. This method involves spreading the chili peppers in a single layer on a flat surface, typically on the ground or on raised platforms, and exposing them directly to sunlight and natural air circulation. During the experiment, the chilies were spread out on clean, dry mats placed on a concrete surface in an open area with good sun exposure. The peppers were arranged in a single layer to ensure even drying. The drying area was selected to maximize exposure to sunlight throughout the day. During the drying process, the chilies were manually turned over periodically (approximately every 2–3 h during daylight) to ensure uniform drying on all sides. This also helped prevent moisture accumulation on the underside of the peppers. At night, the chilies were covered with a clean, dry tarp to protect them from moisture and potential contamination. The tarp was removed in the morning to resume the drying process. The drying continued until the chilies reached the desired moisture content, which typically took several days depending on weather conditions. No artificial heat sources or mechanical air circulation was used in this method, relying entirely on natural sunlight and ambient air for the drying process. This method is traditional and widely used; it does not offer control over drying parameters such as temperature and air flow rate.

2.3. Solar-Cum Gas-Fired Dryer (SGD)

At Pakistan’s Arid Zone Research Institute (PARC) in Umerkot, Sindh, a solar-cum gas-fired dryer was installed. Grains, fruits, and vegetables are among the agricultural items that are dried using a solar-cum gas-fired dryer. The dryer mixes gas-fired heating with solar energy to produce drying that is both economical and successful. The dryer’s solar component heats the air as it moves through the drying chamber by utilizing sun energy. Moisture from the product is absorbed by the heated air and is removed by the product as it leaves the chamber.

This procedure enables drying to occur at times of high solar radiation and can drastically cut down on the quantity of fuel required for drying. When there is not enough solar radiation or bad weather, the dryer’s gas-fired component serves as a backup heating source. It can also be used to raise the chamber’s temperature in order to speed up or shorten the drying process. Utilizing solar-cum gas-fired dryers can lower energy expenses while increasing product quality by lowering the possibility of over- or under-drying.

Table 1. Specification of solar-cum gas dryer.

Component	Details	Size
Solar collector	Length	2160 mm
	Width	927 mm
	No. of collectors	8
Drying chamber	Size	2134 mm × 1524 mm × 1524 mm
Trays	Dimensions	610 mm × 720 mm × 610 mm
	No. of trays	120
	Mesh (stainless steel), mesh	4
	Sides made of 1-inch MS angle iron
Solar panels	24-volt poly	3 (250 watts each)
Stand for solar panel	Made of angle iron	3000 mm × 1500 mm × 700 mm
Axial fan	Power	250 w
	RPM	1400
	Dia	18 inches
	No. of blades	6
Inverter	Input AC	220 V
	Input DC	24 V
Dry batteries	Size	12 V
	Capacity	100 A
	No. of batteries	2
Generator	Petrol	01 KVA
LPG cylinder	No. of cylinders	2 (capacity 11 kg)
Base floor	Made of concrete	4′ × 60′ × 4″
Nameplate	Stainless steel	18″ × 12″

shows the dryer’s specifications. The dryer included a solar collector (glass, absorber plate, thermo-pore layer, glass wool, and air duct), a drying chamber (mild steel (MS) sheet of 16 gauge sandwiched with a glass wool layer of 25 mm, MS angle, MS channel, and MS flat), trays, solar panels, a solar panel stand, an inverter, dry batteries, a petrol generator, and an LPG gas cylinder (Figure 1).

2.4. Solar Tunnel Drying (STD)

A solar tunnel dryer is a kind of dryer that uses solar energy to dry things such as food items, agricultural products, and other materials. It is composed of a lengthy, enclosed, tunnel-like structure that is usually built of translucent materials like plastic or glass, allowing light to pass through and heating the tunnel’s interior. The sun’s hot air rises through the material to be dried, drawing moisture out as it does so. The material is arranged on trays or shelves inside the tunnel. The top of the tunnel is then used to release the dried air. A solar tunnel dryer’s design maximizes sunlight exposure while facilitating effective airflow through the material to be dried.

The greenhouse-type solar tunnel dryer consisted of a polythene sheet cover, metallic pipe, door, wire, ventilation, bricks masonry for the foundation, the front and back wall made of bricks, and one hundred wooden trays (2 × 4 ft). The dryer was 62 ft long and 22 ft wide (Figure 2). The detailed specification is in

Table 2. Specification of solar tunnel dryer.

Component	Material	Size
Pipe	GI pipe 2-inch dia, wrapped with heat-resistant tape	30 ft
	No. of pipes	11
	GI pipe 1-inch dia, length	65 ft
	No. of pipes	5
Polythene	0.25 mm thick	2100 ft2
Tray	Wooden tray with GI screen four mesh	2 × 4 ft
	No. of tray	100
Door	Angle iron GI sheet	3 × 6 ft
Wire	Silver wire 20-gauge, length	600 ft
Ventilation	12 wooden ducts covered with GI mesh	0.5 × 1 ft
Civil work	Bricks masonry for foundation, front and back walls made of bricks

.

2.5. The Moisture Content of Hot Chilies

The moisture content of the hot chilies was measured by the following equation and expressed as a percentage of moisture on a dry basis [29].

$$MC={\displaystyle \frac{M_w-M_d}{M_d}}\times 100$$

(1)

MC is moisture content (% db), M_W is the initial weight of the sample (g), and M_d is the dried weight of the sample (g).

2.6. Moisture Shrink

During drying, moisture at the surface of the hot chilies is initially evaporated, and the internal moisture that migrates to the surface is known as moisture shrink. Other factors that may involve the quick drying of food are high temperature, high wind speed, and low relative humidity [30]. The moisture shrink was calculated by Equation (2).

$$MS(\mathrm{\%})={\displaystyle \frac{{MC}_i-{MC}_f}{100-{MC}_f}}\times 100$$

(2)

where MS is moisture shrinkage (%), MC_i is initial moisture content (%), and MC_f is final moisture content.

2.7. The Moisture Removal Rateof Hot Chilies

The drying or moisture removal rate is proportional to the moisture content difference in the drying time required. The following Equation (3) was used to determine the drying rate of chilies.

$$DR={\displaystyle \frac{MS}{t}}$$

(3)

DR is the drying rate (%/h), and t is the time (h) required for drying.

2.8. Measurement of Color Values for Hot Chilies

The seeds from the placenta were removed, the hot chili pods were destalked, and they were split longitudinally into two halves. The sliced pods were ground in a grinding mill (Model 1/T-204, BU Hler, Uzwil, Switzerland) fitted with a 1 mm screen after being oven-dried at 58–60 °C for two days. Up to processing, the chili powder was kept at 20 °C and sealed in plastic bags. The EOA (Essential Oil Association of the USA) method, recognized worldwide, was used to quantify the chili coloring [14]. The color value was calculated by taking the absorbance of a 0.01% w/v solution of the extract in acetone at 458 nm and multiplying it by 61,000. A UV spectrophotometer was used to determine the absorption level (Model UV1201, Shimadzu, Kyoto, Japan).

3. Results and Discussion

3.1. Meteorological Conditions during Experiment

The results of temperature and humidity in the drying time (9:00 to 17:00) for 3 days are shown in Figure 3, Figure 4, Figure 5, Figure 6, Figure 7 and Figure 8. The average temperature values during the drying period varied from 26 to 34, 28 to 44, and 33 to 55 °C for day 1, similarly 26 to 32, 29 to 38 and 32 to 49 °C for day 2, and 24 to 32, 26 to 39, and 32 to 53 °C for day 3 for CD, the STD, and the SGD, respectively. The drying temperature under solar drying continuously varied with increasing drying time. The temperature in the SGD was observed to be much higher than in the STD and CD. On the other hand, the relative humidity was increased in the morning time and then decreased with increased temperature. The maximum humidity (42%) was recorded with the STD, and the minimum (17%) was for the SGD. Throughout the day, the dryer’s heating temperature was, on average, 75% higher than the ambient temperature, indicating superior performance compared to sun-drying in the open air. It was observed that the patterns of the air’s relative humidity and ambient temperature were counterintuitive to one another. Temperature was low and relative humidity was high during the first period. As time went on, the air’s relative humidity drops while its ambient temperature rises, and vice versa.

The ANOVA results for both temperature and humidity (

Table 3. ANOVA and post hoc Tukey’s HSD test of temperature and drying methods.

Source of Variation	SS	df	MS	F	p-Value
Between groups	2584.22	2	1292.11	89.47	<0.0001
Within groups	1128.67	78	14.47
Total	3712.89	80
Post hoc Tukey’s HSD Test
Comparison	Mean Difference	p-value	Significant
SGD vs. ST	8.41	<0.0001	Yes
SGD vs. CD	13.89	<0.0001	Yes
ST vs. CD	5.48	<0.0001	Yes

and

Table 4. ANOVA and post hoc Tukey’s HSD test of humidity and drying methods.

Source of Variation	SS	df	MS	F	p-Value
Between groups	3145.63	2	1572.81	52.36	<0.0001
Within groups	2343.33	78	30.04
Total	5488.96	80
Post hoc Tukey’s HSD Test
Comparison	Mean Difference	p-value	Significant
SGD vs. ST	−7.33	<0.0001	Yes
SGD vs. CD	−14.78	<0.0001	Yes
ST vs. CD	−7.44	<0.0001	Yes

) show highly significant differences among the drying methods (p < 0.0001 for both). Post hoc analysis reveals significant differences between all pairs of drying methods, with the SGD maintaining the highest temperature and lowest humidity followed by the ST dryer, and then CD. Throughout the experiment, the patterns of solar radiation (

Table 5. Solar radiation throughout the experiment.

Time (h)	Solar Radiation (W·m−2)
	Day 1	Day 2	Day 3
09:00	200	192	193
10:00	310	270	290
11:00	433	414	433
12:00	460	451	458
13:00	479	483	478
14:00	380	379	321
15:00	215	201	175
16:00	137	140	143
17:00	127	122	131

) were nearly identical to one another. It was observed that sun radiation was highest in the morning and peaks at noon, when it swiftly declines. There was a 200–470 W·m⁻² variance in solar radiation during the drying period. The research results revealed that while the relative humidity was lower during solar drying, the drying temperature was higher than the ambient temperature. The temperature and relative humidity during the drying phase also varied significantly. The drying process took an average of 20.2 h, resulting in a final moisture content of 5% from an initial 83% [31]. Onion and garlic had moisture reduction rates in the solar dryer of 25% and 60%, respectively [32]. It clearly states that solar drying has a higher drying rate than traditional drying. The results strongly agree with the previous [22,27,33,34].

3.2. Moisture Content of Hot Chilies

Figure 9 illustrates the moisture content of hot chilies during the drying process. The moisture content decreased from 70% to 9.36% in 36 h with the SGD; from 70% to 11.37% in 50 h with the STD; and from 70% to 9.63% for CD in 84 h. It was evident that the solar-cum gas-fired dryer (SGD) achieved the greatest reduction in moisture content percentage in the shortest amount of time. Similarly, the conventional drying method took the maximum time to dry the hot chiles. The drying procedure was deemed to be finished when the red chili attained the equilibrium condition in the moisture removal rate. The SG dryer’s chilies received the maximum amount of solar energy transferred from the collector by forced convection, while the chili samples dried in the conventional dryer received energy from only the incident solar radiation and less energy from the surrounding environment through natural convection. The one-way ANOVA (

Table 6. ANOVA and post hoc Tukey’s HSD test of moisture content and drying methods.

Source of Variation	SS	df	MS	F	p-Value
Between groups	455.89	2	227.95	4.6237	0.0308
Within groups	591.95	9	65.77
Total	1047.84	11
Post hoc Tukey’s HSD Test
Comparison	Mean Difference	p-value	Significant
SGD vs. ST	10.61	0.0412	Yes
SGD vs. CD	17.44	0.0018	Yes
ST vs. CD	6.83	0.3245	No

) revealed a statistically significant difference among the three drying methods (p = 0.0308). The post hoc Tukey’s Honest Significant Difference (HSD) test confirmed and extended the findings from the ANOVA. The SGD demonstrated a statistically significant superior performance compared to both the ST and CD methods. Specifically, the comparison between the SGD and ST showed a statistically significant difference (p = 0.0412), with the SGD achieving a lower mean moisture content by 10.61%. The difference between the SGD and CD was highly significant (p = 0.0018), with the SGD resulting in a lower mean moisture content by 17.44%. In contrast, the difference between the ST and CD was not statistically significant (p = 0.3245), although the ST showed a lower mean moisture content by 6.83%. According to Rabha et al., the chili samples’ moisture content decreased throughout the duration of 123 h and 193 h of drying in the solar dryer and in the open sun, going from an initial moisture content of 589.6% (db) to a final moisture content of 12% (db) [23]. Similar results were reported in previous studies [14,20,35,36,37,38].

3.3. The Drying Rate of Hot Chilies

Figure 10 depicts the drying rate of spicy chilies, split into four distinct phases: AB, BC, CD, and DE. These phases illustrate various stages of the drying process, each impacted by distinct mechanical and environmental elements. Due to the first temperature rise, Phase AB experiences a rapid increase in drying rate over a short period of time. This phase terminates when the product meets the drying chamber’s air temperature. The abrupt increase is related to the high initial moisture content of the chilies and the huge temperature difference between them and the drying air, which allows for rapid moisture evaporation from the surface [39]. Phase BC is a period of continuous drying rate during which the product remains at the temperature of the drying chamber. This phase is distinguished by a balance of heat transfer to the product and mass transport of moisture from its surface [40]. This phase’s duration and prominence vary depending on the drying process due to changes in air flow rates and heat transmission mechanisms. In phase CD, the product’s surface achieves hygroscopic conditions, signaling the start of the decreasing rate period. The drying rate significantly slows as the evaporation zone moves within the chilies. This step is essential in deciding the ultimate quality of the dried product because it involves intricate moisture movement mechanisms inside the chili structure [41]. Phase DE is the final stage of drying, with minimal moisture content and the product in the hygroscopic field. The drying rate gradually slows, eventually nearing zero. This phase is critical for reaching the desired final moisture content without over-drying, which can have a negative impact on quality characteristics such as color and capsaicin content [42].

When comparing the three drying procedures, the SGD was found to take significantly less time to dry than the STD or CD. This is consistent with the findings of Kumar et al. [26], who showed that solar energy shortened chili drying time by 7 h compared to conventional drying. These findings similarly support those of Hossain and Bala [24], who discovered that maximum drying rates were reached by combining solar and other heat sources. The lack of a real constant rate phase in our investigation, with chilies drying at a decreasing rate throughout the process, is consistent with Akpinar’s [40] observations for diverse agricultural goods. This effect is due to chilies’ complicated cellular structure, which requires moisture to travel from their interior tissues to the surface.

According to Srisittipokakun et al. [43], the greater vapor pressure of water accounts for the faster drying rate observed at higher temperatures in the SGD. Many food-drying processes exhibit initial fast drying rates near the surface, followed by a slowing down as the moisture content drops [44].

The one-way ANOVA conducted on the drying rates of chilies revealed a statistically significant difference among the three drying methods (p = 0.00003) (

Table 7. ANOVA and post hoc Tukey’s HSD test of drying rate and drying methods.

Source of Variation	SS	df	MS	F	p-Value
Between groups	2	76.5123	38.2562	12.7643	0.00003
Within groups	54	161.6234	2.9967
Total	56	238.1357
Post hoc Tukey’s HSD Test
Comparison	Mean Difference	p-value	Significant
SGD vs. ST	0.7368	0.0412	Yes
SGD vs. CD	1.9474	0.0001	Yes
ST vs. CD	1.2105	0.0023	Yes

). The extremely low p-value (p < 0.05) indicates strong evidence against the null hypothesis of equal means, suggesting that at least one drying method differs significantly from the others in terms of drying rate. So, the post hoc Tukey’s HSD test was conducted for further insights, and the following was observed: SGD vs. ST—significant difference (p = 0.0412), with SGD showing a higher mean drying rate by 0.7368 g/g. SGD vs. CD—highly significant difference (p = 0.0001), with SGD showing a higher mean drying rate by 1.9474 g/g. ST vs. CD—Significant difference (p = 0.0023), with ST showing a higher mean drying rate by 1.2105 g/g.

The more dramatic decreasing rate region, which is characterized by thicker, wrinkled, and shrinking skin, implies greater heat and mass transfer resistance. This structural shift, which is more noticeable in the SGD due to the higher temperatures, has a substantial impact on the drying kinetics in the later stages of the process [42]. It was observed that the SGD required a shorter drying time than the STD and CD, which is consistent with the findings of Kaewkiew et al. [22], showing the efficiency of combined heat sources in chili drying. This shorter drying period not only improves processing efficiency but may also aid in the retention of quality features, while more research on specific quality measures such as capsaicin content is required to corroborate this notion.

3.4. Quality of Dried Red Chilies

Color is an essential parameter to indicate the quality of a product. The demand for a product at the market level depends upon those parameters.

Table 8. Color values of SGD, STD, and CD.

Drying Method	Color (EOA Unit)
Solar-cum gas-fired dryer	3422 ± 45
Solar tunnel dryer	3316 ± 38
Conventional	2953 ± 52

± values indicate the standard deviation with three replications.

shows the results of the color value of hot chilies. The color of the CD chilies was dull compared to the STD and SGD product because the chilies were exposed to the open sun on the ground; therefore, the CD products may have been affected by dust, dirt, and animals. However, there was no significant difference in the color value of the STD and SGD because these methods were utterly secure methods in which external factors did not affect the product. The results are in line with [12].

This study provides valuable insights into the performance of different drying methods for hot chilies. However, it has several limitations including quality indicators such as capsaicin content, energy consumption, or environmental impacts that are crucial for the chili processing industry. Future research should address these limitations by incorporating a wider range of quality parameters, conducting rigorous tests, and evaluating the energy efficiency and environmental footprint of different drying techniques, particularly the solar-cum gas-fired dryer (SGD).

4. Conclusions

The performance of three dryers, including a solar-cum gas-fired dryer (SGD), solar tunnel dryer (STD), and conventional drying (CD), was compared in the present study. The SGD consistently outperformed the other methods, achieving the highest temperature (55 °C) and lowest relative humidity (17%). The ANOVA results showed significant differences among the drying methods for both temperature and humidity (p < 0.0001). The SGD also demonstrated superior moisture content reduction, significantly outperforming both the STD and CD (p < 0.05). Among the three methods (p = 0.0308), post hoc Tukey’s HSD tests showed that the SGD significantly outperformed both ST (p = 0.0412) and CD (p = 0.0018), achieving lower mean moisture content by 10.61% and 17.44%, respectively. In terms of efficiency, the SGD reduced the moisture content of red chilies from 70% to 9.36% in just 36 h, compared to 50 h for the STD and 84 h for CD. The highest drying rate was observed for the SGD over the STD and CD. Additionally, the SGD and STD better preserved the color of hot chili samples compared to CD. These findings indicate that the SGD is the most technically suitable method for drying hot chilies, offering improved efficiency and quality retention.