INTRODUCTION
Research rationale
Fruit plays a crucial role in a healthy diet, providing essential vitamins, minerals, fiber, and water These nutrients are vital for maintaining a balanced diet and promoting overall well-being.
Vietnam, a tropical country renowned for its diverse fruits, particularly stands out for its popular bananas, including varieties like "chuoi tieu" and "chuoi bom." Numerous studies highlight the health benefits of bananas, making them a valuable addition to the diet However, their perishable nature poses challenges for long-term storage after harvesting.
Harvesting bananas is crucial as it directly influences the selling price and overall success of the crop With a short growth cycle of just 3 to 4 months from flowering to harvest, enhancing harvest efficiency and ensuring banana quality is essential Additionally, diversifying the range of banana-based food products can significantly increase their value Popular banana products include dried bananas, banana jam, banana wine, and banana powder Among these, dried bananas are particularly favored, though they often retain 20-25% moisture content, complicating commercial preservation This research focuses on producing flattened dried bananas with a reduced moisture content of 10%, which not only diversifies banana products but also extends their shelf life.
Research’s objectives
This study investigates the impact of physiological maturity on the drying process of flattened dried bananas, specifically the Tay cultivar, in Bac Kan province It also examines key technical parameters involved in the drying process and proposes a laboratory-scale procedure for producing flattened dried bananas.
Research’s content
Content 1: Standardizing drying mode suitable for flattened dried bananas
Content 2: Determining the physiological maturity of raw banana suitable for processing flattened dried bananas
Content 3: Studying the effects of some browning treatment on flattened dried bananas
Content 4: Proposing the production process of flattened dried bananas in the form of Bac Kan
Limitations
Limitations are expected to be encountered throughout the study:
1 The number of devices is limited, so some experiments with repeated devices are easy to overlap with the experiments of other students, which can affect the progress of the experiment
2 Due to time limitation, therefore effectiveness of preservation for long has not checked yet
3 The specialized language in English of mine is limited It is predicted that there will be some rooms needed to be improved and corrected
Meaning
This report helps to determine the most suitable conditions for a high quality flattened dried banana product
Based on that, we can propose a plan to complete the manufacturing process of producing flattened dried bananas.
LITERATURE REVIEW
Introduction to the banana tree
2.1.1 Origin and classification of banana tree
The banana tree, scientifically known as Musa sinensis, belongs to the Musaceae family and is derived from two wild banana species: Musa acuminata and Musa balbisiana Native to regions such as Indochina, Indonesia, the Philippines, Japan, and various Pacific islands, bananas are now cultivated in 120 countries, making them the second most produced fruit globally, following oranges The banana export industry plays a crucial role in the economies of many countries across the Americas, Latin America, Southeast Asia, and Africa.
Vietnam is home to a diverse range of banana varieties, each contributing to the region's unique specialties However, the quality and yield of these bananas vary across different areas Vietnamese banana varieties can be classified into five main groups based on their morphological characteristics.
Figure 2.1 Classification of banana in Vietnam [22]
There are also varieties of “chuoi man” “chuoi la” “chuoi hot” but these varieties are grown a little because of low economic value [22]
2.1.2 Morphological characteristics of the flattened dried Bac Kan
Banana tree is a long-standing crop of the locality, easy to grow and suitable for the climatic and soil conditions of Bac Kan province
Trees typically reach heights of 2.5 to 4.5 meters and feature green stalks with long, broad leaves The undersides of these leaves often display a white chalky layer, while the leaf bases are heart-shaped and the leaf stalks are round and still open.
The optimal planting season for bananas is from July to early August to achieve a summer harvest before the rainy season The entire growth cycle from planting to flowering takes approximately 6 to 10 months, followed by a 60 to 90-day period from flowering to harvest Banana plants produce clusters known as bunches, with each bunch containing 15 to 20 fruits, and typically, each plant can yield 3 to 20 bunches The overall weight of a single bunch ranges between 30 to 50 kg.
To assess the ripeness of a banana, people often use the PCI banana peel color scale
Table 2.1: The relationship between the ripeness and the color of the banana skin
8 More flecked with brown than yellow
Figure 2.2: The relationship between the ripeness and the color of the banana skin [16]
2.1.4 The nutritional value of bananas
Bananas are nutrient-dense fruits, providing 100-125 kcal per fruit They are rich in essential vitamins such as carotene, B1, C, pantothenic acid, folic acid, and inositol, alongside important mineral salts, pectin, and polyphenol compounds The mineral content in bananas is also notable, contributing to their overall health benefits.
Table 2.2: The nutritional composition of bananas (per 100gr) [17]
Nutrional value Green banana Ripe banana
Bananas are beneficial for gut health and digestion, serving as a rich source of prebiotics when ripe Additionally, they offer a quick supply of essential electrolytes like potassium, which plays a crucial role in regulating heart rate and maintaining water balance in the body.
A medium-sized banana contains approximately 3g of fiber, which accounts for 10% of the daily recommended intake This fiber offers numerous health benefits, including promoting healthy colon function, regulating cholesterol and blood pressure levels, and reducing inflammation Additionally, foods high in fiber, like bananas, can enhance feelings of fullness, leading to lower energy consumption and supporting weight loss efforts.
2.1.5 The economic value of bananas
Bananas are a crucial tropical fruit with significant economic value As per 2017 data from the FAO, approximately 5.6 million hectares worldwide are dedicated to banana cultivation The banana industry has seen remarkable advancements in yield, with the average production rising from around 14 tons per hectare.
1993 to 20 tons / ha in 2017 (FAO, 2018)
Banana tree has long been a familiar crop to the Vietnamese people The banana is considered as a favorite agricultural product with domestic and foreign consumption market
The current price of banana for domestic consumption is 5,000-6,000 VND / kg
Bananas are a significant export product for the country, particularly to markets in China and Europe, generating substantial foreign currency revenue As a result, the cultivation area for bananas has expanded from the Northern Midlands and Mountain provinces to the Southern Delta, with production now occurring in both small, scattered plots and more concentrated areas covering tens of hectares.
Vietnamese people have long utilized fresh bananas to create a variety of products, enhancing their economic value and providing farmers with a stable income Beyond consumption, the banana stalks are transformed into useful items such as mats, paper, and handicrafts, showcasing the versatility of this agricultural by-product Additionally, bananas are processed into diverse products like dried bananas, banana jam, banana wine, banana juice, and banana powder Notably, flattened dried bananas have emerged as a promising commodity, offering a reliable income source and serving as a specialty for various regions, with significant potential for both domestic consumption and export.
Production and consumption of dried fruit products in Vietnam
The food and beverage industry in Vietnam has experienced impressive growth, with a compound annual growth rate of 9.43%, as reported by the international business monitoring organization (BMI) Notably, dried agricultural products have surged even more, boasting growth rates between 20% and 30%, highlighting their significant market potential.
Asia remains the primary export market for Vietnamese dried fruits, with key destinations including Taiwan, Japan, Singapore, Indonesia, Thailand, and China Notably, China accounts for nearly 80% of Vietnam's dried fruit exports.
In the first nine months of 2013, the export turnover of dried fruits and vegetables to China reached over $225 million, marking a significant increase of more than 43% compared to the previous year This growth positions China as the leading market for these exports, far surpassing Japan and the United States, which rank second and third, respectively.
The market for dried fruits, including popular options like bananas, jackfruit, and longan, presents significant opportunities both domestically and internationally Bananas, in particular, are a staple fruit deeply connected to Vietnamese culture, making them a key product in the dried fruit sector.
Technology for preserving and processing bananas after harvest
Bananas are a highly valuable fruit, but their perishable nature necessitates effective post-harvest preservation to maintain their market price and ensure crop success During transportation and storage, bananas are vulnerable to microbial infections, including anthrax, black stalks, and stem rot To extend the shelf life of fresh bananas, it is essential to implement disease prevention measures, including both physical and chemical disinfection methods, prior to long-term storage.
The popular postharvest banana preservation techniques in Vietnam today includes: cold storage, chemical treatment (most commonly treatment with Topsin M-
Post-harvest banana processing methods not only extend the shelf life of fresh bananas but also maintain their nutritional value and facilitate food import and export under unfavorable conditions In Vietnam, popular banana products include dried bananas, banana jam, banana wine, banana juice, and banana powder.
In particular, flattened dried bananas not only overcome the disadvantages of quickly spoiling bananas but also bring many outstanding advantages such as:
- The dry matter content of the drying product is higher than the fresh product at the same weight
- Strong taste and create new feelings for consumers
- Reducing moisture so storage time is prolonged.
The process of producing flattened dried bananas
According to reference as well as practical observation, the basic stages in the manufacturing process of handmade flattened dried bananas are carried out in the following stages:
Figure 2.3 Process of processing flexible dried flattened bananas
The process of making flattened dried bananas, commonly referred to as dried bananas, is carried out in various craft villages, including Tran Hoi in Ca Mau and Loc Yen in Quang Nam As illustrated in the diagram, the traditional method of producing these handcrafted dried bananas employs straightforward drying techniques that do not necessitate advanced machinery.
Dry technology is cost-effective and simple to implement at the household level, resulting in affordable products with high profit margins due to minimal labor and technological requirements.
The traditional drying process for bananas typically takes 3-5 days and relies on sunlight, making it time-consuming and challenging to implement in industrial settings This method also raises concerns about food safety and hygiene due to prolonged exposure to the elements To address these issues, research and development have focused on creating a modernized production process for flattened dried bananas, optimizing conditions to enhance product quality while ensuring food safety and hygiene standards are met.
Some methods of drying bananas
It is divided into 2 categories:
Natural drying relies on environmental elements like sunlight and wind, making it a time-consuming process that requires ample drying space This method poses challenges in regulating moisture levels, as the final product's dryness is heavily influenced by weather and climate conditions, often resulting in higher moisture content.
Artificial drying involves the use of heat through drying agents like oven smoke, hot air, or superheated steam, which are removed from the equipment once the drying is finished This method enables a quick drying process, allowing for precise adjustments to the product's temperature and moisture content as needed.
Some popular artificial drying methods today are:
Convection drying is a widely utilized method for drying fruits and nuts, where heat is transferred from the drying medium to the material through convection This process effectively removes moisture, making it a popular choice in food preservation.
Cold drying is a refrigeration-based method that utilizes very dry air at temperatures lower than typical drying conditions, specifically ranging from 35-60°C During this process, the water concentration in the drying air is maintained between 10-30%, and the drying occurs under atmospheric pressure.
Infrared radiation drying: is a method of drying moist materials using the source of infrared rays as the main agent to evaporate water in food [13]
Contact drying method: Heat is supplied to the drying object by contacting the drying object with the heat source surface [13]
Food drying must satisfy the following requirements:
- Raw materials must be fresh, clean, and hygienic
The drying method is suitable for the food specification and equipment
- Only use the right temperature to inactivate the enzyme and dry food without affecting the quality of the product Avoid excessive and sudden the use of heat
Once food is dried, it should be rapidly cooled and sealed in a vacuum or inert gas to prevent moisture reabsorption Additionally, compressing the dried food into a cake form can minimize its surface area exposed to humid air, further preserving its quality.
- When drying, they must be stored in clean, cool and dry warehouses The best suitable water concentration for storage is 70%.
Browning during banana processing and storage
Enzymatic browning in bananas diminishes their sensory properties, altering their color, flavor, and texture (Martinez and Whitaker, 1995) This process contributes to significant economic losses, with billions of dollars lost due to the declining value of fruits and vegetables, as reported by the United Nations Food and Agriculture Organization and Consumer Affairs Magazine.
The main groups of reactions that lead to browning Maillard’s reaction such as the caramelization and chemical oxidation of phenol (Manzocco et al., 2001) and the enzyme reaction [12]
Enzymatic browning negatively impacts the quality of fresh fruits and vegetables, despite its role in enhancing color and flavor in products like tea and coffee Fruits and vegetables such as apples, pears, bananas, peaches, lettuce, and potatoes are particularly prone to browning during processing and storage, which not only affects their appearance but also diminishes taste, flavor, consistency, and nutritional value To extend shelf life and mitigate enzyme-induced browning, various treatments are employed A study by Bico et al (2009) found that soaking bananas in solutions like calcium chloride, citric acid, and cysteine, combined with controlled atmosphere methods, can effectively inhibit browning enzyme activity for up to five days.
Browning phenomenon process is without enzyme involvement
Browning reactions in foods without the presence of enzymes include:
- Mailard reaction: is a chemical reaction between amino acids and reducing sugars (saccharose, aldehydes, cetone)
Ascorbic acid is crucial in the browning process of concentrated vegetable and fruit juices, with its oxidation reaction leading to the breakdown of ascorbic acid and the production of brown biochemical CO2 Additionally, caramelization involves the thermal reduction of sugars, resulting in volatile compounds that contribute to the distinctive flavor and brown color associated with caramel.
Factors influencing browning in the processing of flattened dried bananas
2.7.1 Effect of temperature on drying
Higher drying temperatures accelerate the drying process of bananas; however, flattened dried bananas exhibit poor heat resistance In humid conditions, temperatures exceeding 60°C can lead to protein denaturation, while temperatures above 90°C initiate caramelization of fructose and promote strong polymerization reactions Excessive heat can also result in burnt bananas Therefore, the optimal drying temperature for producing flattened dried bananas is between 70°C and 90°C.
2.7.2 Effects of enzymes in bananas
The blackening phenomenon in bananas during processing and preservation varies with different banana varieties and ripeness levels This darkening can be classified as either enzyme-related or non-enzyme-related The enzymes primarily responsible for this process are proxydase (PO) and polyphenoloxylase (PY) PY, a copper protein found in molds and higher plants, contributes to the darkening of cut fruits and vegetables, including bananas On the other hand, PO is an iron-containing enzyme associated with phenolic compounds Both PO and PY can undergo oxidation through interactions with various organic substances, leading to the formation of dark pigments.
2.8 Researches on methods to deal with browning in banana preservation and processing
Enzymatic browning in fruits and vegetables, such as potatoes, apples, and bananas, is caused by the metabolism of phenolic compounds, primarily driven by the enzyme polyphenoloxidase This enzyme can be effectively inactivated through high-temperature treatments, such as blanching or cooking, which help to limit its activity and prevent browning.
Sulfur dioxide (SO2) is utilized to generate compounds like sulfite, sodium sulfite, and sodium metabisulfite, which effectively inhibit browning reactions in food However, its application has limitations, particularly when heat treatment can lead to undesirable structural changes and off-flavors The typical dosage for preventing browning in sliced potatoes is 0.01M Research indicates that SO2 is also effective in preventing enzyme-induced browning.
The use of NaCl is primarily effective for preserving peeled fruits prior to processing, as a concentration of 0.1% can inhibit browning reactions in various products In apple preservation, a combination of salt water and chlorogenic acid is utilized to maintain a pH of 5 However, higher salt concentrations are seldom employed due to their impact on the taste of the food.
Enzyme activity is significantly influenced by pH levels, with a decrease to 4.0—achieved by adding citric, ascorbic, or other acids—resulting in inhibited enzyme function To prevent browning in fruits and vegetables during home preparation, it is common to use lemon juice or vinegar.
Dehydration occurs when water molecules are extracted from a product, inhibiting the PPO enzyme without destroying it, as this enzyme requires sufficient water to function properly To maintain optimal taste and quality, it is essential to avoid heat dehydration during the drying process.
- Borates and borate salts: prevent enzyme browning, with 1.5% sodium tetraborate completely prevents enzyme browning [4]
Research subjects
Bananas are grown in Bung village, Duong Quang commune, Bac Kan province Bananas were harvested in Winter - Spring 2020
Figure 3.1 Bananas sample selected in the area of Bac Kan province
Study location and time
Location: Laboratory of Department of Biotechnology - Food Technology, Thai Nguyen University of Agriculture and Forestry
Research scope
Equipment, tools and chemicals material
The research topic uses the following equipment and tools:
Table 3.1: Equipment and tools used in research
No Equipment and tools Manufacturer
Research content
Content 1: Standardizing drying mode suitable for flattened dried bananas
Content 2: Determining the physiological maturity of raw banana suitable for processing flattened dried bananas
Content 3: Studying the effects of some browning treatment on flattened dried bananas
Content 4: Proposing the production process of flattened dried bananas in the form of Bac Kan
Research Methods
The selection of bananas is based on maturity levels tailored to the specific requirements of each experiment, utilizing three bunches from the center of the chamber The bananas are peeled, with fibers removed, then browned for 15 minutes before being dried whole at 90°C for 45 minutes Following the drying process, the bananas are pressed into a circular mold with a diameter of 10 cm and a thickness of 3 mm, and subsequently dried according to the designated drying regime for each experiment.
Product quality assessment criteria includes:
Each experiment was repeated 3 times The experiment was performed using the one factor The results of the previous experiment will be fixed for the next experiment
3.6.1.1 Experiment 1: Studying on drying mode suitable for processing flattened dried bananas in pieces
Bananas selected at a maturity level of 7 on the PCI scale undergo a thorough processing where all skin and fibers are removed They are then treated in a 0.5% NaCl solution for approximately 15 minutes to achieve browning Following this browning process, the bananas are placed on a tray and dried alongside whole fruits at a temperature of 90°C for 45 minutes.
Bananas that have been dried whole fruit will continue to be pressed in circular molds with 10cm diameter, 3mm thickness and being dried in 5 different drying recipes:
Table 3.3: Different drying recipe for flattened dried bananas
Temperature and drying time Total drying time (hour)
Product quality evaluation criteria includes: Water concentration (%), total soluble solids (° Bx), total organic acid content (%), overal acceptance
Each experiment was repeated 3 times Each recipe uses 8 bananas Results of experiment 1 will be fixed for the next experiment
3.61.2 Experiment 2: Studying the ripeness of the fruit, which is suitable for processing dried flattened dried bananas
Bananas with varying ripeness levels of 6, 7, and 8, as per the fruit color rating scale, were categorized as CT6, CT7, and CT8 The bananas were peeled, knob-cut, and excess fibers removed before undergoing a browning treatment in a 0.5% NaCl solution for approximately 15 minutes Following this treatment, the bananas were dried on a tray alongside whole fruits at a temperature of 90°C for 45 minutes.
Dried whole bananas are shaped into circular molds with a diameter of 10 cm and a thickness of 3 mm, utilizing the drying method determined in Experiment 1.
Product quality evaluation criteria includes: Water concentration (%), total soluble solids (° Bx), total organic acid content (%), overal acceptance
Each experiment was repeated 3 times Each recipe uses 8 bananas Results of the determination of the ripeness of the bananas in experiment 2 that will be fixed for the next experiment
3.6.1.3 Experiment 3: Studying the effects of some pretreatment methods on dried flattened dried bananas
Raw bananas were chosen based on their ripeness from Experiment 2, then peeled and cleaned of surrounding fibers The bananas were subsequently browned in various solutions for approximately 15 minutes, following the experimental formula outlined in Table 3.2.
Table 3.4: Different pre-treatment solution for dried flattened bananas
After browning, bananas are dried whole at 90°C for 45 minutes Once dried, the whole fruits are pressed into a circular mold measuring 10cm in diameter and 3mm thick, using the drying mode determined in the first experiment.
Product quality evaluation criteria includes: Water concentration (%), total soluble solid (° Bx), total organic acid content (%), overal acceptance
Each experiment was repeated 3 times Each recipe uses 8 bananas The results of experiment 3 will be fixed for the next experiment
3.6.1.4 Experiment 4: Studying the effect of the concentration of pretreatment solution on dried flattened dried bananas
Experiment 4 was conducted in the same way as experiment 3 Treating bananas with the selected solutions according to the results of experiment 3 with different concentrations for 15 minutes
After browning, bananas are dried at 90°C for 45 minutes on a tray with whole fruits The dried samples are then pressed into a circular mold with a diameter of 10 cm and a thickness of 3 mm, followed by the drying mode chosen from the initial experiment.
Product quality evaluation criteria includes: Water concentration (%), total soluble solid (° Bx), total organic acid content (%), overal acceptance
Each experiment was repeated 3 times Each recipe uses 8 bananas
3.6.2 Methods of analysis of research criteria
3.6.2.1 Methods of determination of moisture
Determination of moisture by drying to constant mass [11]
Principle: Using heat evaporates the water in the drying product to a constant mass Weigh the product before and after drying and then calculate the moisture content of the product
- Weighing about 2 - 10g of sample product and place in the drying plate and put in the oven at the temperature of 105 ° C The drying time is at least 2 hours
To determine the moisture content of a product, place the drying cup in a desiccator for approximately 30 minutes before weighing it Continue drying the dishes and products for an additional 30 to 60 minutes, then allow them to cool in the desiccator and weigh again Repeat this process until the weight remains constant The moisture content is calculated as a percentage using the appropriate formula.
W Where: g: Weight of drying cup (g) g1: Mass of the drying crucible with the test piece before drying (g) g2: Mass of the drying crucible with the test piece after drying (g)
3.6.2.2 Determination method of dissolved dry matter [11]
The density of water typically rises as the concentration of dissolved solids increases, particularly when those solids are denser than water This relationship allows for the identification of dissolved substances based on the water's density.
- Weigh 10g dried banana, dilute with 100ml of water Blend well until the bananas and water are homogeneous
- Then take 1 part of the mixture into a filter paper, filter 2-3 drops of the original solution, then drip it on the prism and measure
3.6.2.3 Determination of total organic acid content [11]
- Chemical: 0.1N NaOH; phenolphtalein 0.1% in 60 o alcohol
Weigh 10 - 20 g to the nearest 0.001 g, which used distilled water to transfer the entire sample to a 250 ml triangle bottle, add water to about 150 ml, and heat on a water bath at 80 ° C for 15 minutes To cool and then transfer completely to a 250 ml volumetric flask, make up to volume with water, shake well, allow to settle Filter the sample into a beaker Aspirating 25 ml of the filtrate into a 100 ml flask, adding 3 drops of phenolphthalein 0.1%, titrate with 0.1N NaOH to a stable pale pink color for
- How to calculate the results:
+ V: is the number of ml of 0.1N NaOH used for titration
+ V1: is the number of ml of solution that has been drawn to standardize
+ K: The coefficient of malic acid, K = 0.0067
+ m: mass of sample to be titrated (g)
3.6.2.4 The sensory evaluation method is according to VN Standard 3215: 1979
According to Vietnam Standard 3215: 1979, which outlines the sensory analysis scoring method for food products, the State Science and Technology Commission has established guidelines for assessing the quality of dried banana products This standard provides a systematic approach to evaluating food quality through sensory scores, focusing on organoleptic criteria such as appearance, color, flavor, and taste.
The point system used is a 20 point system, built on a unified scale of 5-point grades (from 0 to 5) Product quality classification is based on the following table:
Table 3.5: Standards regulating product quality
Table 3.6: The importance level for the evaluation criteria
Name of indicator Coefficient of importance
Overall acceptance is based on industry standard 10 TCN 482: 2001 on flattened dried bananas that is issued by the Ministry of Agriculture and Rural Development:
- Color: from light brown to dark brown
- Flavor: characteristic sweetness of dried bananas, can be slightly acrid
- Appearance: pressed flat into pieces with a thickness of 1.5 - 2mm, diameter of 7-8 cm In the same package, the pieces must be similar in size and color
- Structure: flexible, not hard and dry
- Weight: the product is packed in a vacuum bag, 500gr weight
Data are the results of 3 repetitions, calculated using the One-way ANOVA with post-hoc Tukey HSD program (Stata).
RESULTS
Effects of ripeness on quality of Bac Kan bananas
Determining the ripeness of raw bananas is crucial for producing high-quality flattened dried bananas, as variations in ripeness affect starch, sugar, and tannin content To achieve optimal organoleptic and nutritional value in the final product, it is essential to select the appropriate ripeness of banana pulp In our experiment, we examined three different degrees of ripeness, and the results are presented in Table 4.3.
Table 4.3: Effect of ripeness on the quality of flattened dried bananas
Light yellow, the surface has many reddish streaks, the state is dry
Brown yellow, quite soft, slightly dry at the edge of the banana
The color of the cockroach's wings, the state is soft, and has a honey sheen
(Note: In the same column, values with at least one letter do not differ in significance level α = 0.05)
Figure 4.6 Dried bananas at maturity 6
Figure 4.7 Dried bananas at maturity 7
Figure 4.8 Dried bananas at maturity 8
The ripeness of bananas significantly influences the quality of flattened dried banana products, as indicated by data from Table 4.3 and Figures 4.6, 4.7, and 4.8 As bananas ripen, moisture and total soluble solid content increase, while total organic acid content decreases, leading to varying quality parameters in the dried product Notably, quality indicators for CT6, CT7, and CT8 show a significant difference at α