INTRODUCTION
Research rationale
Vegetables and fruits are essential components of a healthy diet, providing vital nutrients that support body growth and enhance the immune system, while also preventing diseases like cardiovascular issues and stroke They are rich sources of important vitamins such as C, B1, B3, B6, and B9, along with minerals and dietary fiber In Vietnam, fruits and vegetables not only serve as a crucial food source but also contribute significantly to the economy by creating jobs and boosting agricultural development As of mid-March 2017, Vietnam's fruit and vegetable exports reached nearly $543 million, marking a 26.7% increase compared to the previous year, with exports to over 60 countries worldwide.
Vietnam's climate, characterized by a tropical monsoon environment, features four distinct seasons: Spring, Summer, Autumn, and Winter, along with rainy and dry seasons This diverse climate supports a variety of fruit trees, including litchi, jackfruit, avocado, oranges, tangerines, apples, and durian, with oranges thriving in regions like Tuyen Quang, Bac Giang, Ha Giang, Hanoi, Hung Yen, Vinh, and Nghe An Oranges are highly beneficial, offering a rich source of vitamin C, fiber, and low calories, while promoting cardiovascular health However, fresh oranges are prone to damage during transportation and storage due to physiological and biochemical factors, leading to significant post-harvest losses of 15-30%, which can increase during distribution Therefore, implementing effective post-harvest processing techniques is crucial to minimize quality loss in Vietnam.
The market offers a variety of trusted orange-based products, including orange candy, juice, syrup, and jam Among these, candied orange slices remain under-researched due to the complexities involved in their production, from raw material processing to bitter flavor elimination These slices are crafted from thinly sliced fresh oranges, where the bitterness of the skin is reduced and combined with sugar and honey to enhance flavor while ensuring health safety This processing method not only preserves the fruit but also extends its shelf life to up to one year, resulting in a product that differs significantly from fresh fruit While dried fruit jams made from other ingredients like pineapple and bananas are widely available, candied orange slices are scarce in the market, with little research conducted on their large-scale production.
This study aims to process candied orange slices from various orange varieties in Vietnam, focusing on their nutritional and sensory qualities The goal is to diversify market offerings and enhance income for orange growers.
“ Research on the production process of candied orange slices ” at the laboratory of The faculty of Biotechnology and Food Technology.
Research’s objectives
Set up a process of candied orange slices products with high nutritional value, convenience, safety in use, and contributing to the diversification of orange products on the market
- To determine the effects of the bitter elimination method on product quality
- To determine the ratio of mixing orange and sugar on product quality
- To determine the effects of temperature and drying time on product quality
- Evaluate the quality of the product candied orange slices finished product
- Establish a process for processing the product's candied orange slices.
Research questions and hypotheses
- Do we use salt water to remove all bitter taste of orange peel?
- Can we use other types of sugar add-in?what are other types of sugar?
- What is the effect of honey on the final product?
- What is the appropriate drying temperature?
- If we use 5% salt water, then candied orange slices will be de-bitter
- If we choose the ratio of oranges and sugar is 2:1, then the candied orange slices product will have a pertinent sweet taste
- If choosing the temperature for drying is 55 o C in 24h, then the product will be safe humidity
Limitations
- The research is implemented in the laboratory, the equipment and machines are limited, cannot be done on a large scale and modern equipment such as the factory
- This is a new product that has never been studied before, so it takes time to research and experiment.
Definitions
Candied orange slices are a delightful treat made by drying orange pieces with sugar at high temperatures, resulting in a product that contains approximately 90% dry matter This crispy, sweet snack combines the natural flavor of oranges with a sugary coating, making it a perfect addition to desserts or a standalone snack.
LITERATURE REVIEW
The scientific basis of the thesis
Oranges, scientifically known as Citrus sinensis, are part of the citrus family and come in various sizes depending on their variety These fruits are characterized by their sweet and slightly sour flavor when ripe.
Citrus fruits, particularly oranges, have a rich history with various origins Evidence suggests that orange trees date back to 2200 BC in China, while some believe they are native to the Himalayas in India Oranges gained popularity in India before spreading to East and Southeast Asia By the 3rd century BC, orange trees made their way to Europe, flourishing in the Mediterranean regions Christopher Columbus introduced orange trees to America, which later expanded to Australia and Africa through local growers Today, orange cultivation is widespread across many countries worldwide.
Figure 2.1 Sanh orange and Vinh orange Structure of orange trees:
- Stems and branches of orange: Stems of woody type, semi-bush, with 4-6 main branches, 2 - 3m tall trees, low branches Spike direction, sparse, horizontal branching
- Orange leaves: Staggered leaves, longleaf, dark green, oval, 5-10cm long, 2.5-5cm wide, with a thin tooth edge; petioles with wings, 4-10mm wide Leaves with small ears [9]
Orange flowers typically bloom in the spring, producing numerous blossoms, though only a few will mature into fruit These small, white flowers grow in clusters and emit a light, pleasant fragrance.
Orange roots, similar to those of woody plants, efficiently absorb water and mineral salts Their root system is characterized by a shallow, broad, and dense structure, primarily found in topsoil and porous soils Notably, root growth is most vigorous during February and September, with optimal development occurring in the first eight years of the plant's life.
- The oranges fruits are spherical, with a thin rind, orange-yellow when ripe, sweet, or slightly acidic [20]
Some varieties of oranges are grown in Vietnam:
Vinh orange, a citrus fruit native to Vinh in Nghe An, Vietnam, is characterized by its round shape and succulent texture, featuring a vibrant yellow hue with green undertones This delightful fruit comes in various varieties, including Xa Doai, Van Du, Song Con, and Navel oranges, each offering unique flavors and qualities.
Xa Doai orange (Citrus sinensis 'XA DOAI') is a Spanish-origin orange variety cultivated in Vietnam This fruit comes in two shapes: high and oval, with an average diameter of 6.8-7.8 cm and a weight ranging from 200 to 250 grams Typically containing 10-12 segments, these oranges are juicy and feature thick peels measuring 2-3 cm When ripe, the peel boasts a vibrant yellow color.
• Song Con oranges imported by a French plantation owner planted on Dao Nguyen production hill (today's Song Con Farm) should be named "Song Con oranges"
Song Con oranges are characterized by their thin skin, high water content, sweetness, and delightful fragrance After 3-4 years of growth, these oranges begin to yield a high productivity, demonstrating excellent resistance to pests and diseases, making them well-suited for various mountainous midland regions.
The Van Du orange, introduced to the Van Du orange farm in 1947, was developed through a careful selection process to ensure high quality This robust tree features a broad canopy and large, dark green leaves, producing medium-sized fruits that are juicy but contain numerous seeds The unique flavor profile of the Van Du orange is characterized by a deep sweetness complemented by a hint of bitterness that quickly fades after consumption.
Navel oranges, also referred to as umbilical oranges, are native to California and were introduced to Vietnam in 1937 These oranges are still found in various farms across the country On average, a navel orange weighs about 230 grams, with some reaching up to 290 grams, and has a diameter of approximately 7.6 cm When ripe, the fruit exhibits a yellowish-gray color and typically contains 11 to 12 sections filled with dark yellow pulp.
Hai Duong oranges, primarily cultivated in Thanh Ha and Tu Ky districts, are renowned for their large size, typically weighing between 300 to 700 grams and measuring about 10 cm in diameter These oranges are characterized by their striking red-yellow skin and white cloves Each fruit contains 20 to 30 large, flat seeds and offers a unique flavor profile that combines sour and bitter notes, making them a distinctive variety in the region.
+ Sanh orange (C reticulata x C Sinensis: king mandarin)
The Sanh orange, the most popular orange variety in Vietnam, is easily identifiable by its thick, bright green skin Its flesh is dark orange and sweet, making it a favorite among locals.
Typical of king mandarin: Bo Ha oranges, Ha Giang, Tuyen Quang, Yen Bai,
Bo Ha oranges are grown in Bo Ha, Yen The district, Bac Giang province Bo Ha orange is suitable with mountainous midland, cool and humid climate
Ha Giang, Tuyen Quang, and Yen Bai are renowned for their high-quality oranges, primarily grown in northern Vietnam and harvested during the Tet holiday Among these, Tuyen Quang province is particularly famous for its Ham Yen oranges, known for their exceptional taste and quality.
+ Sweet orange (Citrus sinensis L.Osbeck)
Oranges are a popular fruit, averaging around 100g, with thin, easily peelable skin that can be yellow, red, or dark red There are several main varieties of oranges, including Canh orange from Hanoi, Dong Du oranges from Hai Phong, and Ngoc Cuc and Hanh Thien oranges from Nam Ha Additionally, Bu oranges and Sour oranges, known for their slightly sour taste, are commonly found in Huong Son (Ha Tinh) and Tuyen Hoa (Quang Binh) Voi oranges, or big oranges, weigh between 300-350g and are a hybrid of Bu oranges and grapefruit, primarily cultivated in Tuyen Hoa (Quang Binh).
The composition of an orange consists of the following:
The outermost layer of citrus fruits, known as the flavedo, can be orange or blue depending on the variety This layer is rich in essential oil sacs, contributing a robust flavor that resembles the taste of the orange pulp.
The white part of the rind (albedo): contains pectin and cellulose, has nearly the same amount of vitamin C as the flesh and other nutrients [13], [20]
Carpels with juicy vesicles: the inside contains, the orange cloves are cell fluids
A section of an orange: in it cure the orange cloves and the cell fluid
Orange seeds: hold sprout, include endosperm, embryo, seed coat [9]
Central column: The part located in the center of the orange, containing pectin and cellulose[9]
Table 2.1 Physical parameter of a sweet orange fruit [26]
1 Fruit color Yellow, orange, green
5 The average number of segment 10
9 The thickness of flavedo (mm) 1.8
Citrus is a valuable fruit tree on the international market, being one of the most traded fruits Moreover, this is a fruit with high nutritional value
Table 2.2 The nutritional composition of fresh orange (USDA) [33]
Nutritional composition of orange per 100 gram
Nutritional composition of orange per 100 gram
Fresh oranges are primarily composed of carbohydrates and water, with minimal amounts of fat and protein The sweetness of fresh oranges comes from sugars such as glucose, fructose, and sucrose Despite their relatively high sugar content, oranges have a low glycemic index, ranging from 31 to 51, which is classified as low (below 55) according to The University of Sydney's glycemic index scale This low glycemic index indicates that oranges offer numerous health benefits.
The importance of the orange industry to people and the economy
2.2.1 The importance of the orange industry to people
Oranges are a nutrient-dense fruit, packed with vitamin C, fiber, folate, and antioxidants, while being low in calories and sugar Incorporating oranges into your daily diet can significantly nourish your body and promote overall health.
Orange juice is a health-boosting beverage rich in flavonoids and hesperidin antioxidants, as noted by M.D Nguyen Thi Hang, Vice Chairman of the Department of Eastern Medicine at the Vietnam Academy of Traditional Medicine Its high vitamin C content helps lower blood pressure, while its nutrients function as a diuretic, promoting the kidneys to excrete excess salt and water This combination enhances the body's resistance and combats fatigue.
Consuming orange juice with a pinch of salt after intense exercise is an effective method to quickly restore energy and hydration The natural fructose and high water content—85%—in oranges are rapidly absorbed by the body, providing a refreshing boost and enhancing recovery.
Enhance eyesight: Orange is rich in carotenoids and vitamin A These substances help enhance eyesight, especially good for women who have problems with macular degeneration [34]
Anti-cancer: Scientists have recently published the results of the prevent-cancer effects of orange juice It contains flavonoid substances like hesperidin and naringenin
Laboratory studies have shown that orange juice reduces childhood leukemia, as well as combating breast, liver, and colon cancers [31]
Reducing the risk of cardiovascular disease: Studies have shown that orange juice can help reduce the risk of heart disease because it can help improve blood circulation [34]
Oranges are rich in beta-carotene, a potent antioxidant that safeguards skin cells from damage and shields the skin against free radicals, helping to prevent the visible signs of aging.
Weight-loss support: A large orange contains 4 grams of fiber and only 87 calories Therefore, eating oranges helps you to prevent hunger, limit junk food habits
In addition, oranges are also rich in mineral vitamins to help you always feel healthy, full of energy [31]
To prevent viral infections, it's essential to consume foods high in polyphenols, which can enhance your immune system Oranges are particularly beneficial as they are rich in polyphenols, offering anti-viral, anti-inflammatory, anti-allergic, anti-carcinogenic, and anti-proliferative properties.
2.2.2 The importance of the orange industry to people and the economy
Orange trees thrive in tropical climates and are relatively easy to cultivate, making them a popular choice among farmers Varieties like gourmet oranges are particularly lucrative, offering high returns By implementing techniques for off-season flowering, farmers can enhance the selling price of their citrus crops, significantly boosting their income.
The expansion of domestic and international markets is driving job creation and income growth, enhancing the economic well-being of farmers while boosting export revenue With just 1.5 hectares of land, farmers can achieve impressive yields of over 80 tons per crop, contributing significantly to the overall economy.
Orange trees are increasingly proving their value in enhancing farmers' economic development To ensure sustainable productivity, it is essential for the agricultural sector to facilitate farmers' access to advanced techniques, reliable seed sources, and stable markets for their produce, allowing them to focus confidently on cultivation.
The situation of orange production and consumption in Vietnam and worldwide 16 2.4 Products made from oranges
2.3.1 The situation of orange production and consumption in Vietnam
Figure 2.6 Area planted oranges in Vietnam from 2005 to 2018
Based on the chart, we can see that the area of oranges growing from 2013 to
Since 2018, Vietnam has significantly increased its orange cultivation area from 75,000 hectares to over 120,000 hectares within five years This expansion reflects the country's commitment to investing in orange farming, which not only enhances productivity but also contributes positively to economic development.
Figure 2.7 Orange production in Vietnam
Despite a decrease in the area planted with oranges from 2005 to 2013, orange production showed a consistent increase, indicating improved productivity per area Since 2013, there has been a significant expansion in the area dedicated to orange cultivation Notably, in 2016, orange production rose by 10.9% compared to 2015, and in 2017, it further increased by 18.7%.
2016, an increase of 151 thousand tons [35]
Cao Phong District in Hoa Binh Province is renowned for its significant orange production, boasting 2,080 hectares of citrus fruit, with 1,367 hectares dedicated to oranges as of February 2017 Over 900 hectares of this area are actively cultivated, yielding more than 23 million tons in 2016, and generating an average price of 25,000 to 35,000 VND per kilogram This thriving orange industry provides a substantial income for local farmers The annual harvest season typically runs from August to May, featuring a variety of early, main, and late-maturing orange types.
Sanh orange, cultivated across more than 7,000 hectares in 13 communes, involves over 4,000 households and yields an annual production of 80,000 to 100,000 tons, generating an estimated value of over 650 billion VND Recognized for its quality, Sanh orange received a branding certificate from the National Office of Intellectual Property in 2007 and ranks among the "Top 50 Famous Vietnamese Specialty Fruits" and "Top 10 Famous Brands in Vietnam." Meanwhile, Vinh orange, grown in Nghe An's Quy Hop region, spans over 2,000 hectares with an average productivity of 27 tons per hectare, with some areas exceeding 45 tons per hectare annually, providing significant returns for growers.
In Vietnam, orange products are meticulously processed to ensure food hygiene and safety, maximizing the use of the fruit from skin to pulp and minimizing waste This approach not only supports orange growers by utilizing lower-grade fruit but also generates additional income The health benefits of these orange-based products are significant, including orange peel jam, cough syrup, and essential oils for steam baths that promote mental refreshment and treat common ailments like fever and runny nose Furthermore, these products, such as orange wine and jam, enhance the value of the Vietnamese orange brand, showcasing the versatility and health benefits of this beloved fruit.
2.3.2 The situation of orange production and consumption worldwide
Figure 2.8 Orange production worldwide from 2012/2013 to 2018/2019
(in million metric tons) (M Shahbandeh, 2019)
From 2012 to 2019, global orange production experienced notable fluctuations, starting at 49.85 million metric tons in 2012/2013 and rising significantly to 54.28 million metric tons by 2018/2019.
Figure 2.9 Leading orange producing countries worldwide in 2018/2019
(in million metric tons) (M Shahbandeh, 2019)
In the marketing year 2018/2019, Brazil emerged as the world's leading orange producer, generating 20.16 million metric tons This accounted for approximately 37% of the global orange production, which totaled 54.28 million metric tons that year.
Following by Food and Agriculture Organization of the United Nations, Statistical Bulletin, 2016; production of oranges of all countries in the world from
From 2008 to 2016, major orange-producing countries in the Northern Hemisphere included the USA, Italy, Spain, Egypt, Turkey, Mexico, China, India, Indonesia, Iran, and Pakistan In the Southern Hemisphere, Brazil and South Africa were prominent producers.
Orange juice: It has bright colors and a refreshing flavor extracted from fresh oranges and concentrated fresh orange juice and pasteurized to further retard spoilage
We can use orange juice to adds to drinks, candies and sweets
Orange peel extract is elaborated with orange peel and orange core The product is the perfect options for beverages, soft drinks, or food applications
Dry orange juice powder is a versatile ingredient that can enhance a variety of products, including ready-made meals, jams, syrups, and flavorings It is also commonly used in orange-flavored tea and as an additive in baked goods such as cookies, icings, and cakes.
Orange syrup is primarily used in soft drinks and beverages, but its versatility extends to the production of ice creams, dairy products, baked goods, ready meals, jams, and various other syrups This syrup typically has a brix level ranging from 41.0 to 44.0, highlighting its concentrated sweetness and flavor.
Orange Essential Oil is a natural product derived from the peels of various Citrus Sinensis fruits It is extracted using a mechanical cold-pressed method, ensuring no thermal treatments are applied To preserve its beneficial properties, the oil is promptly packaged in drums immediately after extraction.
Fruit jams are products made from fresh or semi-prepared fruits cooked with sugar to dryness of 65-70% Featured jam products are sweet, naturally pure aroma of berries
Fruit jams often contain added sugars in addition to the natural sugars present in the fruit, while their high acidity helps inhibit microbial activity Pectin, a natural coagulant found in fruit, is essential for the proper consistency of most jams Over time, jams may experience separation, initially appearing on the surface before spreading throughout the product Storing jam at low temperatures, maintaining a pH below 2.8, or exposing it to impurities and mechanical stress can accelerate its decomposition.
Jam classification: according to the state of product structure
- Processing from juice or fruit pure
- Create gel coagulated with pectin or agar
- There are 3 types: Jelly, Jam, Marmalade
- The dry matter content is about 60-65%
- Soft, slightly wet, no more sugar syrup around the product
- The dry matter content is about 70-75%
- Outside there is a sugar coat crust
Candied orange slices are a delightful treat made by combining orange pieces with sugar and drying them at high temperatures This process results in a product with approximately 90% dry matter, resembling crispy dried jam.
General process of producing candied orange slices
Flow chart 1 General process of producing candied orange slices
The research titled "Research on Greening Disease Prevention and Trial Planting of New Orange Varieties in Ham Yen, Tuyen Quang Province, Vietnam" outlines a comprehensive procedure for producing high-quality oranges This procedure includes the selection of disease-resistant orange varieties, effective planting techniques, and the implementation of disease prevention strategies to ensure optimal growth and yield By following these steps, farmers can enhance the sustainability and productivity of orange cultivation in the region.
Raw materials used to produce products must be of good quality, achieve maturity, a state of hardness and no defects, no smashing, meeting the standards of TCVN 1873: 2014
The fruits after selection and classification are washed to remove all impurities and microorganisms adhering to the crust
After washing, cut off the stem, the fruit is cut into thin slices, remove the seed, remove broken orange, and unsatisfactory orange piece to prepare for the next step
Soaking in lime water helps to increase the firmness of the product and removes some of the bitter substance in the orange peel
- Put the orange pieces into the prepared lime water and soak for 10 hours
- Rinse with clean water after soaking
Adding sugar to products not only enhances sweetness but also extends shelf life Meanwhile, orange peels contribute to flavor enhancement and preservation However, it is essential to properly treat the orange peels before incorporation to minimize bitterness, which can negatively impact the quality of candied orange slices.
Soaking the sugar will help the orange pieces to soak into the sugar, while the melted sugar will avoid localized burning when concentrated
- Put the sugar into orange after draining
- After mixing sugar, let stand for 12 hours for the orange to soak into the sugar and dissolve
- Concentrate orange slices on low heat to avoid burning the product due to caramelized
- During the concentration process, stir well and do gently to avoid broken orange pieces
- Orange pieces after concentration will be uniform yellow, dry sugar will stick around
The drying process of product works to lose some of the water in the product, the product is drier, flexible, does not drain, and preserves longer
Procedure: The drying stage is used by specialized dry ovens
- Spread the orange pieces after concentrating on the drying tray
- Put the drying tray into the oven
Purpose: To continue releasing the remaining steam in the product, and to lower the temperature of the product, helping to prevent water when packaging
Procedure: After drying, remove the tray from the oven Cooling the product in two ways is a natural cooling and forced cooling:
+ Natural cooling: A method to cool after drying in the room and slowly
+ Forced cooling: As a fan-cooling method, this cooling method has advantages over natural cooling which is faster cooling time, the product is less changed
Purpose: To help the product is isolated from the outside environment, prolong the time of storage and use of the product
+ Prepare packaging: Can use PE bags or glass jars, plastic jars to contain products
Fully print product information on the package including product name, net weight, ingredients, production date, expiry date, instructions for use, address of the manufacturer, etc
+ In the bag: Need to seal the mouth of the bag (PE bag) or tighten the cap tightly (glass and plastic vials)
To extend the shelf life of high-sugar products, it is essential to store them under cold conditions, ideally between 3 to 7 °C While the storage process may not prevent water leakage, proper refrigeration on a small scale can effectively maintain product quality.
CONTENTS AND METHODS
Material
Raw oranges, primarily Chanh Orange and ripened varieties, are sourced from Thai Nguyen city The selected raw materials must adhere to specific technical ripeness standards, ensuring that the fruit is free from rot and damage, and possesses a natural fragrance, in accordance with TCVN 1873 - 2014.
- Sugar of Thanh Hoa company reaches TCVN 6959:2001, salt of Van Ninh company reaches TCVN 9639:2013
- Lime has been purchased at Thai market - Thai Nguyen City
3.1.2 Research instruments, equipment, and chemicals
Table 3.1 Research instruments and equipment
A dehydrator machine effectively dries fresh fruits while preserving their essential nutrients This versatile equipment is also utilized in the production of jam and candied orange slices, significantly reducing processing time compared to traditional sun-drying methods Additionally, using a dehydrator ensures higher quality products, enhancing food safety and hygiene standards.
3.1.3 The location and duration of research
- Location: Faculty of Biotechnology and Food Technology – Thai Nguyen University of Agriculture and Forestry
Methods
3.2.1.1 Research on choosing the bitter elimination method of fresh orange
Table 3.3 Research on choosing the brine solution to the bitter elimination method of fresh orange
Formula Salt (ratio salt/water (%) Fixed factor
- Soaking time in lime water: 10h
Assessing the structure, flavor, taste, and color of the product, we used the sensory evaluation method After sensory evaluation, we have the result, and using the
The use of SPSS software for statistical analysis has determined the optimal salt-to-water ratio and soaking time for processing oranges in saltwater, which is essential for producing high-quality orange jam Key index values identified in this experiment include color at 0.8, taste at 1.2, and both flavor and structure at 1 Notably, the application of salt effectively eliminates bitterness, significantly enhancing the overall taste of the final product, making taste the most critical index in the formulation.
3.2.1.2 Research on choosing the ratio of orange and sugar to product quality
Table 3.4 Research on choosing the ratio of orange and sugar to product quality
Formula 1 1.5:1.0 - Soaking time in lime water: 10h
- Ratio of Salt and water: was selected in experiment 1
In Experiment 2, three formulas with varying ratios of orange and sugar were tested Unlike Formula 1, Formula 2 exhibited distinct characteristics, with a color rating of 1.2, a taste rating of 1.2, a flavor rating of 0.8, and a structure rating of 0.8 The sugar content significantly impacts both the taste and color of the final product; excessive sugar results in an overly sweet taste and a brown color post-drying, while insufficient sugar leads to a bland flavor After careful evaluation and scoring, the optimal orange-to-sugar ratio will be determined for subsequent experiments.
3.2.1.3 Research on choosing drying temperature on product quality
Table 3.5 Research on choosing drying temperature on product quality
Formula Temperature (ᴼC) Fixed factor
Formula 1 50 - Soaking time in lime water: 10h
- Ratio of salt and water: was selected in experiment 1
- Ratio of Orange and Sugar: was selected in experiment 2
In this experiment, key indices were established for color (1.2), taste (0.8), flavor (0.8), and structure (1.2), highlighting the significance of color and structure in selecting the optimal drying temperature and time Given their high importance scores, these factors are critical in ensuring product quality After thorough evaluation and scoring, the best drying temperature will be determined to finalize the production process.
3.2.1.4 Evaluate the quality of the product candied orange slices finished product
- Determination of the moisture content by the method of drying to constant weight (TCVN 10788:2015);
- Determination of soluble dry matter content by refractometer (TCVN 4414:1987);
- Determination of vitamin C content in the product by the titration method of 0.01N iodine (Nguyễn Văn Mùi (2001))
- Determination of total organic acid content by the neutralization method with NaOH 0.1N (TCVN 4589:1988);
- Determination of total sugar content by Bertrand method (TCVN 4074-2009)
3.2.2 Physical and chemical analysis methods for evaluating the quality of the product candied orange slices finished product
3.2.2.1 Determining the moisture content by drying method to constant weight according to TCVN 10788:2015 [15]
- Principle: Use heat to evaporate the water contained in the sample From the mass difference before and after drying, the moisture content of the orange sample is calculated
3.2.2.2 The method of determining the content of soluble solids by refractometer according to TCVN 4414 – 1987 [13]
Light refraction occurs when light passes from the atmosphere into a liquid, causing the light ray to bend if the liquid is a water-soluble solution By analyzing the deviation of light rays, we can assess the concentration of dissolved solids in the solution The refractometer provides a direct reading of this concentration as a percentage at a temperature of 20°C.
3.2.2.3 Methods of determining vitamin C content [5]
- Principle: Ascorbic acid has strong reducing is oxidized with iodine solution with the indicator is a starch solution:
In the presence of vitamin C, the I3- ion is reduced to iodide ion Once all the vitamin C is oxidized, iodine and I3- appear in the solution, reacting with starch to produce a dark blue color, which indicates the endpoint of the titration.
3.2.2.4 Method of determining total organic acid according to TCVN 4589:1988
Organic acids dissolve readily in water, allowing for the quantification of these acids in a sample through direct titration with sodium hydroxide solution using phenolphthalein as an indicator.
3.2.2.5 The method for determining the total sugar content by the method Bertrand according to TCVN 4074-2009 [12]
The principle involves extracting total sugar from the sample using hot water, followed by hydrolyzing the sugar into glucose with hydrochloric acid (HCl) The glucose is then quantified through reactions with Fehling solution, iron (III) sulfate, and potassium permanganate.
3.2.3 Evaluating sensory quality by the method of the quality scoring (TCVN
The sensory quality of the product was evaluated during production testing using the scoring method outlined in TCVN 3215-79 This assessment focused on key attributes such as structure, flavor, taste, and color, employing a sensory evaluation approach to ensure comprehensive analysis.
In a controlled environment free from disturbances, seven trained individuals participated in sensory tests, where uniform lighting and water for rinsing between samples were provided All testing conditions were standardized, and the order of sample presentation was randomized Prior to testing, unique codes for each sample were prepared, and results were recorded and analyzed using SPSS software (Khetra, Y., Kanawjia, S K., & Puri, R (2016)) The sensory evaluation adhered to Vietnamese standards (TCVN 3215 - 79), which employs a systematic approach for assessment.
20 points built on a unified system scale of 6 steps (from 0 to 5) and a score 5 is the highest for an indicator [11], [20], [23]
Following the sensory evaluation, we obtained results that were analyzed using SPSS software The statistical analysis employed a univariate analysis of variance, incorporating fixed factors and dependent variables to assess the data from each sample.
We use the analysis of variance (ANOVA) to analyzed all scores of the sensory evaluation, to determine whether there were significant differences between means for each variable [23].
RESULTS
Research on choosing the bitter elimination method of fresh orange to product
To develop a product that satisfies market demands and enhances economic efficiency, it is essential to identify the optimal mixing ratio of raw materials.
An experimental study was conducted to investigate the effect of different brine concentrations (0%, 2.5%, 5.0%, and 7.5%) on the elimination method of orange peel Quality assurance salt, in accordance with TCVN 9639:2013, was dissolved in water at varying concentrations for the experiment The oranges were soaked in the saltwater solution for 10 hours, while other parameters remained consistent as outlined in Table 3.3 The sensory evaluation results are presented in Table 4.1.
Table 4.1 Results for research on choosing the bitter elimination method of fresh orange to product quality
The ratio of salt/water (%) Formula 1 (0%) Formula 2 (2.5%) Formula 3 (5%) Formula 4 (7.5%)
(Note: Values in the same row with different exponents have significant differences at α = 0.05)
Table 4.1 illustrates that the bitter taste significantly affects the aroma and flavor of dried orange jam, with the bitterness being influenced by the salt concentration used for soaking 10 kg of oranges in each experiment Orange jam with a salt ratio of 0-2.5% still retained a bitter taste, while a 7.5% salt solution in Formula 4 minimized bitterness but resulted in an overly salty flavor and soft, crushed oranges Formula 3, using a 5% salt ratio, produced a slightly bitter taste while enhancing the product's color and aroma Soaking the oranges in brine for 10 hours effectively reduced bitterness and preserved some characteristics of the orange peel Notably, Formula 3 received the highest sensory evaluation scores across four criteria: color (4.14), taste (3.77), flavor (4.00), and texture (3.86).
To ensure product quality, the optimal mixing ratio was determined to be 3:1, using 1 kg of salt dissolved in 20 liters of water for every 10 kg of fresh oranges, with a soaking time of 10 hours before proceeding to the next experiment.
Research on choosing the ratio of orange and sugar to product quality
In our study, we initially determined that a 5% brine solution effectively mitigates the bitter taste of fresh oranges Following this, we conducted a second experiment to explore the optimal sugar-to-orange ratio, testing combinations of 1.5:1.0, 2.0:1.0, and 2.5:1.0 The purpose of adding sugar was to enhance the aromatic sweetness, thereby improving processing and storage capabilities To ensure the sugar permeated the oranges, we soaked them in a concentrated sugar solution while avoiding excessive heating to prevent burning, which could negatively impact the color, taste, and texture of the fruit The sensory evaluation results for the material proportions are detailed in Table 4.2.
Table 4.2 Result for research on choosing the ratio of orange and sugar to product quality
The ratio of orange: sugar (kg:kg) Formula 1 (1.5:1.0) Formula 2 (2.0:1.0) Formula 3 (2.5:1.0)
(Note: Values in the same row with different exponents have significant differences at α = 0.05)
Table 4.2 reveals significant differences in the average sensory criteria across various formulas at a significance level of α = 0.05 Formula 2 achieved the highest quality scores for color, flavor, taste, and structure, while Formula 3 showed a decline in these scores, and Formula 1 recorded the lowest ratings overall.
In evaluating the quality indicators, Formula 1 received low scores for color and taste, with ratings of 3.0/5.0 and 3.86/5.0, indicating insufficient sweetness and a less appealing color after drying compared to other formulas While Formula 3 scored higher than Formula 1, it still fell short of Formula 2, achieving scores of 3.43/5.0 for color, 3.42/5.0 for flavor, 3.5 for taste, and 3.79/5.0 for structure, suggesting a favorable reception among sensory evaluators However, the 2.5:1.0 ratio of oranges to sugar resulted in an overly sweet taste that masked the flavor of orange peels, with excessive surface sugar diminishing the product's fresh orange characteristics.
Formula 2, with a mixing ratio of 2.0 to 1.0, achieved the highest sensory evaluations, scoring 4.36 for color, 4.5 for taste, 4.21 for flavor, and 4.36 for structure This product features a distinctive orange hue, a harmonious taste, and a light fragrance.
Therefore, we selected the most appropriate ratio of orange and sugar mixing in formula 2 was 2: 1 to do the next experiments.
Research on choosing temperature on product quality
Drying is an essential process that reduces moisture in materials to ensure product stability and extend shelf life In this study, drying temperatures between 50°C and 60°C were analyzed until the desired humidity levels were achieved The sensory quality of the product was subsequently evaluated, with results detailed in Table 4.3.
Table 4.3 Results for research on choosing the temperature and drying time on product quality
(Note: Values in the same row with different exponents have significant differences at α = 0.05)
Drying temperature significantly influences product quality, as shown in Table 4.3 At temperatures between 50°C and 60°C, the sensory quality varied notably, with Formula 2 achieving the highest total score, followed by Formula 1, while Formula 3 scored the lowest Increasing the drying temperature to 60°C resulted in reduced moisture content, enhancing moisture loss Drying at 55°C achieved a safe moisture level without compromising quality compared to 50°C, while also reducing drying time and implementation costs Formulas 1 and 2 exhibited favorable sensory scores for color and structure, maintaining product characteristics, whereas Formula 3 resulted in an unsatisfactory dark brown color and dry texture.
Based on Table 4.3, we selected formula 2 with the drying temperature of 55 o C to complete the product.
Evaluate the quality of the product candied orange slices finished product
After finalizing the production parameters for candied orange slices, the product is packaged in high-heat soldered tin zip bags, with each bag weighing between 200-500g A quality assessment conducted after six months of storage at normal conditions (20-25°C) is detailed in Table 4.4.
Table 4.4 The content of nutrients and microbiological criteria in candied orange slices products
Total dry matter content ( o Brix) 81.82 c 74.85 b 69.40 a
(Note: Values in the same row with different exponents have significant differences at α = 0.05)
Moisture content is essential for yeast and mold growth, with high humidity facilitating mold spore germination Mold growth is minimal at 20% relative humidity but accelerates significantly at 75%, often appearing within weeks Our analysis revealed that the moisture content in the product was low (14-19%), effectively inhibiting mold growth for up to one year Additionally, the high sugar content (50.20 - 62.28%) in candied orange slices further prevents microbial growth After six months, the candied orange slices maintained their flavor and successfully inhibited mold growth, demonstrating the importance of both low moisture and high sugar levels in food preservation.
Candied orange slices maintain a Vitamin C content ranging from 16.85 to 28.83 mg%, with an average of 28.83 mg%, which meets 32.03% of the daily value (DV) requirements The total organic acid content is between 164.35 and 203 mg%, while the total dry matter content varies from 69% to 81% These findings indicate that even after six months of storage, the nutritional value and flavor of the product remain intact Consequently, candied orange slices are of high quality and nutritional value, allowing for an anticipated preservation period of up to one year.
Establish a process for processing product candied orange slices
Based on the above experiments, we propose the technology procedure for producing candied orange slices as shown in the below:
The production process of candied orange slices (10kg fresh orange)
Flow chart 2 The flow chart of the production process of candied orange slices
4.5.2 Description of the production process of candied orange slices
Figure 4.1 The main materials: Chanh orange and Sugar Step 2 Washing fresh orange
The fruits after selection and classification are washed to remove all impurities and microorganisms adhering to the crust by clean water
Step 3 Cutting the orange into slices orange
- After washing, cut off the stalk, the fruit is cut across the citrus into thin slices (about 0.5cm to 0.6cm) from the stem to the bottom
- Getting all the seeds out
- Remove the pieces of orange torn, unsatisfactory
Figure 4.3 Cutting slices orange and remove the seed Step 4 Soaking the sliced orange in brine water
- Soak the orange pieces in 20 liters of 5% brine solution
- Purpose: To eliminate a part of bitter substance in orange skin
+ Put the orange pieces in the prepared saline and soak for 10 hours
+ Rinse with clean water 2-3 times to remove residual salt
+ Drain and make the process of soaking in lime water
Figure 4.4 Soaking the sliced orange in brine water Step 5 Soaking in lime water
- Soaking the orange with the rate of 10kg of fresh oranges in 20l of freshly prepared lime water
- Purpose: to increase the crispy of the product
- Rinse with clean water from 2-3 times to remove all lime water
Figure 4.5 Soaking in lime water Step 6 Mixing with sugar
- The mixing ratio between oranges and sugar is 10kg of fresh oranges and 5kg of sugar
- Purpose: Soaking the sugar will help orange pieces to soak into the sugar, and melting sugar will avoid local sugar melting when concentrated
+ Pour sugar into orange after draining, can mix sugar in brass or pan
+ After mixing sugar, let stand for 10-12 hours to infuse orange pieces
+ Concentrate the slices orange on low heat to avoid burning the product due to caramelization
+ During the concentration process, it is necessary to stir and perform gently to avoid broken orange pieces, maybe a chopstick for each hand to make the mixing easier
+ During the concentrate step, we add 20ml of honey to create a fragrance for the product
+ Orange pieces will gradually turn yellow
+ Orange pieces after concentration will be uniform yellow, have a thin layer of sugar surrouding the orange pieces
Figure 4.7 Concentrate by boiling sugar solution Step 8 Drying by drying oven
- Purpose: The drying process of orange jam has the effect of losing a quantity of water in the product, the jam is drier, flexible, not watery, and preserved for longer
- Procedure: The drying step is used by drying ovens
+ Spread the orange pieces after concentrating on the drying tray
+ Put the drying tray into the oven, the number of trays according to the design of the oven
+ Close the oven door and set up a time to dry for 24 hours
Figure 4.8 Drying orange pieces bt đ rying oven Step 9 Cooling
- Purpose: To continue releasing the remaining steam in the product, and to lower the temperature of the product, helping to prevent steam when packaging
- Procedure: After drying, remove the tray from the oven Cooling the product in two ways is a natural cooling and forced cooling:
Natural cooling is an effective technique used to lower the temperature of products after the drying process By allowing items to cool at room temperature, this method can reduce their temperature from 55°C to the surrounding ambient temperature, ensuring optimal conditions for storage and further processing.
+ Forced cooling: As a fan-cooling method, this cooling method has advantages over the natural cooling method which is faster cooling time, the product is less changed
- Purpose: To help the product is isolated from the outside environment, prolong the time of storage of the product
+ Prepare packaging: we use PE bags to contain products
Fully print information on the packaging, including product name, net weight, ingredients, production date, expiry date, instructions for use, address of the manufacturer,
+ In the bag: sealing of the bag PE bag
Figure 4.9 Packaging the candied orange slices product
Despite the high sugar content of the products, their low water content can lead to water leakage during storage To prolong the shelf life, it is essential to store them in a cold environment at temperatures between 3-5°C For smaller quantities, refrigeration is an effective method for preserving jam.
CONCLUSION AND RECOMMENDATIONS
Conclusion
Research conducted at the Faculty of Biotechnology and Food Technology, Thai Nguyen University of Agriculture and Forestry, has led to significant findings regarding the processing of candied orange slices The experiments carried out in the laboratory have provided valuable insights that contribute to our understanding of this product.
Soaking fresh oranges in a 5% saltwater solution effectively reduces the bitterness of the orange peel, resulting in a milder flavor while preserving the natural taste of the fruit.
Determining the ratio of mixing orange and sugar was 2.0:1.0 The resulting product was a harmonious sweet taste and a slight aroma
Determining the drying temperature was 55°C for 24 hours to create a product with a safe humidity of 7.5%, the yellow color of the product
During a six-month storage period, significant changes were observed in the product's composition After processing, the moisture content was recorded at 14.06%, with dry matter content at 81.82° Brix, total sugar content at 62.28%, vitamin C content at 203 mg%, and total organic acid content at 28.83% After three months, these values changed to 16.70% moisture, 74.85° Brix dry matter, 55.46% total sugar, 186.00 mg% vitamin C, and 21.10% total organic acids By the end of the six-month storage, the product exhibited a moisture content of 18.85%, dry matter at 69.40° Brix, total sugar at 50.20%, vitamin C at 164.35 mg%, and total organic acids at 16.85%.
Set up a production process of household-sized candied orange slices product with all accompanying technology parameters.
Recommendations
- Continue to observe and evaluate the quality of the product during storage to give an appropriate storage time
- Registering the quality and trademark of Thai Nguyen University of Agriculture and Forestry for sale on the market
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APPENDICES APPENDIX 1 Sensory evaluation form for candied orange slices product
To evaluate the samples, please examine each one carefully by observing, smelling, and tasting them After your assessment, indicate your preference for each sample using the provided scale Feel free to taste each sample multiple times and ensure to record your responses in the evaluation form.
Note: Please take a sip of water after you finish a sample
Sample Color Taste Flavor Structure
Table 1.1 Basic of scoring for each norm
5 The product is orange yellow
4 The product has a normal orange color
3 The product is dark yellow
2 The product is yellow brown
1 The product is discolored (br coownlor)
1 Strange taste (example: salty taste) Flavor 5 Orange and orange peel flavor
4 Little fragrance of orange peel
3 No fragrance of orange peel
APPENDIX 2 The amount of glucose is converted to volume of potassium permanganate solution for titration
Volume of KMnO 4 0.02M solution (ml)
Volume of KMnO 4 0.02M solution (ml)
Volume of KMnO 4 0.02M solution (ml)
Experiment 1 Research on choosing the bitter elimination method of fresh orange
Experiment 2: Research on choosing the ratio of orange and sugar to product quality
Experiment 3: Research on choosing the temperature for drying on product quality.