PRODUCT QUALITY CHARACTERISTICS OF SOLAR DRIED CHILLI PRODUCTS

Solar drying is a drying technology that involves the usage of solar drying panels that are economically and environmentally friendly. The moisture content of chillies can be reduced over a shorter period. The products are protected from contamination from foreign matter, insects, and fungal contamination, thus the high-quality dried chilli. The farmer can easily use this method. Moisture sorption isotherm curves showed the inverse relationship decreasing as the temperature increases at constant relative humidity. The analysis was evaluated using the static gravimetric technique with a salt solution to create different relative humidities. The accelerated shelf life method was used where the chillies were stored in the oven at 56 °C. The analysis was done every two days up to the twelfth day, packed into aluminium packages, glass jars, and plastic containers.

Fresh chillies were dried to reduce losses associated with quality and microbial loss due to the high moisture content of fresh chilies. Drying was done both for oven and solar drying at 60

°C. Different pre-treatment methods involved blanching with hot water at 85-90 °C and acetic blanching at 90-100°C and soaking in pre-treatment of Na2S2O5 and CaCl2 solution for ten minutes. The physiochemical, nutritional, and microbial characteristics of chillies were then analyzed for oven and solar-dried chilli products. With sensory evaluation, consumer testing affective/ preference test was used with the scores noted over the standard seven-point hedonic scale where seven represented "like very much," and 1 represented "dislike very much ." A panel of 22 participants was used. Parameters to be evaluated were Colour, taste, texture, astringency, bitterness, flavour, and overall acceptability. A meat curry stew was used in tasting the chillies with plain white rice as a carrier. Consumer preference questionnaires were given to the participants to fill in as they conducted the analysis.

This study evaluated the quality and safety of solar-dried selected chilli varieties grown in Kenya by solar drying fresh chilli products using solar tunnel driers. Optimizing drying chillies using oven driers, the temperature of 60 °C was found to be the most appropriate as it had minimal effect on the quality characteristics of chillies that included vitamin A, vitamin C, and Colour. The newton model was also used in fitting the drying kinetics data and was found to be a good fit for the data as it had a residual value (Coefficient of determination or R2) close to one of 0.9797 at 60 °C solar drying.

The isotherms also exhibited the phenomenon of hysteresis, where the equilibrium moisture content was higher at a particular equilibrium relative humidity for the desorption curve than for adsorption. The G.A.B. (Guggenheim- Anderson-de Boer) model applied in fitting the experimental data at the temperatures of 50 °C, 55 °C, 60 °C, 65 °C and 70 °C which was found to have good prediction accuracy indicated by the high values of R2 (Coefficient of Determination) and the S.E.E. (Standard Error of the Estimation).

Of the three packagings used, the aluminium package was found to be the best in terms of nutrients retention [vitamin A of 8.9mg/100g, vitamin C of 13.66g/100g and Colour (Colour was however fairly constant in all the three packages at an average of 1.3 arc tan)] after the end of the shelf life analysis. The microbial analysis was, however, higher in the aluminium package at 2.301 CFU/G for the total viable count and 2.699 CFU/G for yeast and mold. This was attributed to inappropriate pre-processing of the chillies before and during drying that increased the microbial load in the final product after drying. The microbial load for glass and plastic packages was 2.699CFU/G and 2.301CFU/G, respectively, for the total viable count with no growth for yeast and mold.

There was a significant difference in all the parameters analyzed, with more beta carotene retention for oven-dried chillies, with the range being 28.4 to 23.2mg/100 g. This was in agreement with reports done by (Kamal et al., 2019). The ascorbic acid quantity was also significantly different, with ranges from 52.44 to 24.32g/100g. The effect of the pre-treatment on Colour was also significant. The microbial analysis showed variations in the microbial also that were attributed to the areas of collection of the chillies or the type of treatment done to the chillies.

There was no significant difference between oven-dried chillies and solar-dried chillies on the parameters of Colour, taste, astringency, bitterness, texture, and overall acceptability. The flavour, however, had some significant differences between solar and oven-dried chillies. The findings will inform on the commercial viability of dried chilli products concerning meeting food safety standards in Kenya to promote the industry's commercialization and value addition of chilli adoption. This can be done by solar drying fresh chillies and effectively storing the finally dried chillie products under aluminium packaging, showing the best nutritional composition preservation. Care should also be taken when handling both before and after drying to prevent recontamination of the final dry product. This study, therefore, will guide the solar drying technique of fresh chillies from the study of the quality characteristics and storage of the finally dried chillies from the moisture sorption isotherm and the storability study. The sensory analysis guided the consumer's acceptability of the finally dried chillies.

 

 

Table 1: Production, Area and Productivity of Major Chilli Producing Countries in 2018 Table 2: Nutritional Value of Chillies [per 100 grams]

Table 3: Tables Showing Quality Characterizes Of Chillies Dried at Different Drying Temperatures.

Table 4: Newton Model Results

Table 5: Water Activities of Various Saturated Salt Solutions Used In Desorption and Adsorption Experiment

Table 6: GAB Equation Model Results For Desorption Data Table 7: GAB Equation Model Results for Adsorption Data

Table 8: Table Showing the Quality Characteristics of Two Chilli Varieties Dried Under Oven Drier at 60 Degrees at Different Pre-Treatments.

Table 9: Table Showing the Quality Characteristics of Two Chilli Varieties Dried Under Solar Drier At 60 Degrees at Different Pre-Treatments.

Table 10: Colour Parameters of Chillies Dried Under Oven Dried at 60 Degrees for Different Pre-Treatments

Table 11: Colour Parameters of Chillies Dried Under Oven Dried at 60 Degrees for Different Pre-Treatments

Table 12: Microbiological Composition of Dried Chillies

Table13: Microbial Quality Of Chillies Stored under Three Different Packages for Shelf Life Analysis.

Table 14: Colour Change of Dried Chillies for the Shelf Life Analysis Table 15: Sensory Evaluation of Dried Chillies

 

Figure 1: Production Share of Chili by Region Figure 2: Jalapeno Chilli Pepper Variety Figure 3: Senorita Jalapeno

Figure 4: Mucho Nacho Jalapeno Figure 5: Bird’s Eye Chilli Figure 6: Cayenne Pepper

Figure 7: Moisture Content versus Drying Time of Chillies at Different Temperatures for Oven and Solar Drier.

Figure 8: Moisture Ratio versus Drying Time of Chillies at Different Temperatures for Oven and Solar Drier

Figure 9: Equilibrium Moisture Content versus Water Activity of Desorption Isotherm at Different Temperatures for Oven and Solar Drier.

Figure 10: Equilibrium Moisture Content versus Water Activity of Adsorption Isotherm at Different Temperatures for Oven and Solar Drier

Figure 11: Vitamin C Content in g/100g against Days of Shelf Life Analysis Figure 12: Vitamin A Content in mg/100g against Days of Shelf Life Analysis

 

 

 

Chilli, used as a vegetable, condiment, or culinary supplementation, is considered an important commercial crop worldwide (Pandit et al., 2020). It is mainly consumed as a dried powder known as chilli powder; it's an important spice worldwide and a potential cash crop (Hossian et al., 2005). Chillies are grown worldwide, with the highest production quantities in China, India, Korea, the United States of America, and Africa (Gupta et al., 2002). The total production of chillies in the world is 4,485,882 tonnes (FAOSTAT, 2020). The tropical climatic condition of Kenya makes farming of chill quite ideal in the country (Kwacha, 2018). The major production areas in Kenya are where the altitude is below 2000m, such as part of the Coastal region, Eastern regions such as Makueni, Machakos, Meru, Murang'a, Kiambu, and Western regions such as Kisumu. Commercial production may require irrigation (International Trade Centre, 2014). The total production of chillies in Kenya is 3,023 tonnes (FAOSTAT, 2020). Losses for chillies occur at different stages in the supply chain, from the farmer to the final consumer. The total loss is estimated at 29.32 %. These values are a 2.33 % loss at the farmer's level, a 5 % loss at the middleman level, 10.80 % at the seller's level, and 11.18 % at the customer's level (Darmawati et al., 2019).

Only Five species of the twenty-five to thirty known species of chilli are domesticated. These are Capsicum   annuum,   Capsicum    frutescens,    Capsicum    chinense,    Capsicum pubescens and Capsicum baccatum (Pandit et al., 2020). Chillies are a rich source of Carbohydrates, Proteins, Lipids, Mineral salts (Calcium, Phosphorus, and iron), Fibre, and Vitamins A, B2, B12, C, D, and E (Orobiyi et al., 2013). Green chillies are also a source of biologically active phytochemicals, including antioxidants known to provide health benefits exceeding basic nutrition (Bhattacharya et al., 2010). Capsaicinoids, naturally occurring alkaloids present in the capsicum species, are the substances responsible for the hotness of heat upon consumption of chilli by humans (Guzman and Bosland, 2017). 

During the pick period of harvest, however, farmers get low returns due to low market prices at the time (Hossain et al., 2005), as freshly harvested chillies are quite perishable. Thus large amounts of product are wasted and lost due to inadequate post-harvest handling and processing facilities (Gupta et al., 2002).

Red chilli has been preserved by direct sun drying. This technique requires large open spaces and takes long periods before the required moisture is reached, as it's dependent on the sunshine hours in an area. Since the chilli to be dried is spread openly outside, there is also contamination by foreign matter (dust, stones), insects, animals, and fungal infestation, which causes low quality and losses in the final product (Fudholi et al., 2013). Spoilage and quality changes of green chilli have also been minimized through cold and humid storage conditions at a temperature of 15 °C. However, with cold storage, care must be taken to avoid chilling injury for chilli stored at temperatures below seven °C (Hameed et al., 2015). Vacuum drying is another method used to preserve herbs and spices, such as chilli, as it produces products with better organoleptic properties. This method is expensive as the equipment used to produce the vacuum is expensive (Guiné, 2018). Greenhouse drying uses thermal mass to collect and store heat energy and insulators to store the collected heat for cloudy days and at night. However, the installation of these is expensive due to the equipment requirements (Samreen et al., 2017).

Solar drying of chilli is an economical and environmentally friendly technology that can be applied in drying of chilli; which can be used in reducing the moisture content of freshly harvested chillies from around 80% to5% with a duration of 48 hours, thus an improvement of the traditionally used open sun drying method (Fudholi et al., 2013). Drying can be combined with pre-treatments such as blanching (done to improve the acceptability of the product) can be used to treat chilli (Gupta et al., 2002). Plastics are currently used as packaging materials because it's cheap, flexible transparent, and not fragile. Plastic is, however, not environmentally friendly as its non-biodegradable. Glass cups and polyvinyl dichloride (PVDC) plastic are other

modes of packaging that can be used to package chilli with minimal influence on the quality characteristics of chilli such as Colour and vitamin C content (Renate, 2019). Vacuum packaging under cold storage is another method that offers better quality characteristics of chilli storing with a way for chilli products of moistures above 10% (Chetti et al., 2014). Therefore, the products need to be processed after harvest and prevent the losses incurred by the farmers by reducing the post-harvest losses with proper post-harvest processing technologies.

Fresh chillies are naturally perishable; thus, large amounts are wasted and lost due to inadequate post-harvest handling technologies. Also, during the pick period of harvest, farmers get low returns for their produce due to a lack of processing units (Geetha and Selvarani, 2017: Hasan, 2012). Significant price fluctuations and decreases result in food waste from unsold chilli (Anoraga et al., 2018). Shriveling, wilting, and strong physiological activities are the most experiences post-harvest problems for fresh green chilli (Hameed et al., 2015). The total loss is estimated at 29.32 %. These values are a 2.33 % loss at the farmer's level, a 5 % loss at the middleman level, 10.80 % at the seller's level, and 11.18 % at the customer's level (Darmawati et al., 2019).

After harvest, farmers take the freshly harvested chillies to the market for sale but due to the perishability nature of the chillies, a large quantity is lost. For farmers that export their chillies, even the smallest delay that caused the chillies to over mature and change colour will make the chillies unsuitable for sale (The Star, 2020). To reduce these losses its important co come up with technology that reduce the post-harvest losses of fresh chillies.

Although cold storage allows products to be available for longer periods in the fresh state for both consumption and processing, chillies are susceptible to cold injury if stored below seven °C or below. Cold storage is also quite expensive and not affordable to many small-scale farmers. An increase in temperature, however, causes an increase in the rate of water loss (Hameed et al., 2015).

The burning sensation resulting from chilli consumption, especially due to capsaicin, is unpleasant to many people, especially those not used to eating chillies. The concentration of capsaicin in chilli pepper depends on the type of variety and its maturity, and this concentration is subject to change. The range of this capsaicin concentration is 0.1 to 1% in chilli peppers (Yang et al., 2019).

Improper post-harvest handling of chilli due to their perishability nature results in losses in quality and spoilage due to wilting, pathogenic disorders, shriveling, and water loss (Hameed et al., 2015). Price fluctuation is also a result of improper post-harvest handling technologies; thus, the crop harvested results in high yield losses (Yanti et al., 2018). The traditional direct sun drying of chilli requires a large, open space, depending on the sunshine hours of the area, thus, a long drying time. The chilli being dried is also likely to be affected by contamination from foreign matter, insects, and fungal infestation due to the moist conditions. This method thus results in poor quality of the final dried product regarding nutritional qualities, microbial load, and general physical appearance.

For this reason, the end product is of lower quality (Fudholi et al., 2013). Sun drying also causes the shrinking of the chillies resulting in an unattractive final product due to the hindrance of the outer layer of this fruit to transfer of water inner surface (Kamal et al., 2019). Solar drying can be either through: direct or open sun drying and indirect solar drying. Under direct sun drying, food products dried are directly heated with solar radiation when spread out into a thin layer outdoors. The end product is thus of higher quality in terms of nutritional quality and microbial load. Solar drying panels as also quite an affordable method of dying chillies compared to open sun drying (Belessiotis and Delyannis, 2011). The colour of red chilli is among the important quality characteristics; drying, however, causes a loss of color quality of the final dried product (Chaethong et al., 2012). Chillies contain three times as much vitamin C as oranges and are loaded with vitamins A and E, folic acid, and potassium (Rohrig, 2014); their consumption is, however, low. This research therefore seeks to utilize the solar drying method to help in the post-harvest losses experienced in chillies through moisture reduction thus making the crop available all year round. Also shelf life study will help understand on proper packaging methods to ensure the final dried product is safe microbiologically and nutritionally.

With appropriate post-harvest technology innovation, losses of red chilli can be reduced from 20-30% to about 3-5%, and these technologies are simply applied at the farmer's level (Yanti et al., 2018). Drying is the main preservation method used today, whose main purpose is to reduce the enzymatic and microbial activity that causes spoilage, therefore, extending the storage life of the food product being dried. Drying also saves packaging, storage, and transportation costs (Montoya-Ballesteros et al., 2014). This will help farmers get more returns from the sale of chillies and make the crop available all year round for consumption.

There has been advancement in drying technologies such as pre-treatment use, techniques, and equipment to accelerate the drying process, enhance quality, and improve the safety of the foodstuff dried. Solar drying is one of the drying techniques used in drying foodstuffs, for example, chilli, whose energy source is the sun (Guiné, 2018). To counter these shortcomings of direct sun drying, the indirect solar drying method is used, which involves the use of thermal energy collecting equipment and driers with special techniques, thus higher drying rates shortening the drying period, zero or no losses from infestation and natural phenomena and also improved quality dried product (Wiriya et al., 2009). Under solar drying, the moisture content of freshly harvested chillies can be reduced from around 80% to 5% within 48 hours (Fudholi et al., 2013). Solar driers reduce drying time and can be applied to improve and provide uniform hygienic conditions at processing (Chaethong et al., 2012). Chillies were therefore dried using the solar drying method to reduce post-harvest losses and also analyze their quality and storage. Chillies also contain three times as much vitamin C as oranges. They are loaded with vitamins A and E, folic acid, and potassium (Rohrig, 2014), thus increasing the nutritional composition when consumed. The findings will inform on the commercial viability of dried chilli products concerning meeting food safety standards in Kenya to promote the commercialization and value addition of chilli adoption by the industry. The dried chillie products can be used packed by different food industries that specialize in spice processing and also combined with other spices to make mixes for sale. Fast food industries can also utilize the dried chillies in preparation of the different foods and with the higher nutritional composition the spice supplement the diet with vitamins and minerals found in chillies.

To evaluate the quality and storability of dried chilli by solar drying of fresh chilli products in Kenya

H1: Drying process kinetics of chilli can be optimized for quality and safety for the final product 

H2: Moisture sorption isotherms of chilli can be determined through desorption and adsorption experiments

H3: Solar dried chilli products will have a good phytochemical composition, high nutritional and microbial quality compared to fresh chilli

H4: Solar dried chilli product will exhibit high shelf life and longer storage stability

H5: The acceptability and preference of the solar dried chilli product will be favourable due to high sensory quality.