Introduction 

The term “dry beans” refers to varieties of beans other than green beans, string beans, and soybeans and can also be known as “common bean”.  The global dry beans market is projected to register a CAGR of 4.3% during the period from 2021 to 2026.  The COVID-19 pandemic and subsequent lockdown restrictions created a surge in demand for dry beans because of their long shelf-life.  Even before the pandemic, there was an increasing inclination towards vegan diets and for people with health issues like diabetes who want to increase fibers and proteins in their diet as well as reduce meat consumption.  Awareness of the benefits of plant-based diets has increased due to the pandemic and made people more health-conscious as well as fueling a desire to boost their immune systems.  The top global bean producers are Myanmar, India, Brazil, China, Mexico, Tanzania, United States, Kenya, Uganda, and Rwanda.  Major importers include India, China, Bangladesh, Egypt, and the United States. Myanmar is the leading producer of dry beans, accounting for over 20% of total global output.  One factor contributing to the high production of beans in Myanmar is the need to use land after rice cultivation instead of leaving it idle.  Beans are planted at the beginning of the winter season and thrive on leftover moisture from the rice season without requiring additional irrigation.  India and China are the largest importers of dry beans from Myanmar, accounting for nearly $600 million in beans combined in 2019.  Coffee beans are another significant type of bean in the global market.  The global market was valued at $9.5 billion in 2019 and is expected to reach around $12.1 billion by the end of 2027, growing at a CAGR of 3.5% from 2021 to 2027.  Market growth is expected to be driven by a growing increase of coffee consumption by consumers, greater awareness of health benefits associated with coffee, and an expansion of the retail market which makes the buying process easier for consumers.  There has also been a marked decrease in the consumption of carbonated drinks which has helped the coffee beans market grow, but increased availability of tea is expected to be a factor in restraining growth of the market. Cocoa beans also make up a very significant portion of the beans market and they are used to make chocolate and various cocoa based products, such as cocoa butter, cocoa powder, and cocoa liquor.  Market size for cocoa beans was estimated at $9.94 billion in 2018 and is projected to expand at a CAGR of 7.3% through 2025. 

Beans are a good and affordable source of numerous nutritional components that offer a myriad of health benefits.  Consumption and demand are increasing as more people look for alternatives to meat that offer some of the nutritional components found in meat.  They offer high protein and amino acid content while being lower in calories and saturated fat than many other protein sources, including meat and dairy products.  Beans are also high in fiber, iron, minerals, and vitamins.  Folate is one vital nutrient found in beans that makes healthy red blood cells and helps prevent neural tube defects in a fetus during pregnancy.  They are also rich in polyphenols, which are antioxidants that help the body fight the effects of free radicals and protect the body from disease.  Some studies have shown that bean consumption can help fight cancer by acting as antioxidants and anti-inflammatory agents.  Other studies suggest that beans can improve heart health.  One such study found a clear correlation between eating beans and a lower risk of coronary heart disease while another suggests that the nutrients in beans can help lower cholesterol, which is a proven risk factor for heart disease and heart attacks.  The high fiber in beans can help stabilize blood glucose levels and thus prevent diabetes.  Another study looked at the effects of consuming one cup of beans per day and there was a reduction in blood sugar levels and lower blood pressure in those who ate the beans.  Replacing animal-based proteins with plant-based protein helps liver health as well.  Fiber and healthy starches help the consumer to feel full and may help prevent overeating and weight loss.  Many kinds of beans enhance gut health by improving intestinal barrier function and may help promote weight loss by feeding healthful gut bacteria colonies.  Coffee beans and coffee are also a rich source of biologically active compounds, such as caffeine, chlorogenic acids, nicotinic acid, trigonelline, cafestol, and kahweol, all of which have significant potential as antioxidants.  As more research is conducted on the health benefits of bean consumption, there will be a need for more fast and non-invasive testing methods for measuring parameters of interest in beans. 

Beans Composition, Harvesting, and Processing  

Beans are the major source of protein, dietary fiber, minerals, and vitamins for many people and these components have the potential to meet 10% to 20% of the recommended daily amount of certain nutrients for adults.  The chemical composition varies greatly at 15% to 30% protein, 60% to 70% carbohydrates, and 0.7% to 2% lipids.  Carbohydrates are composed primarily of starch, followed by dietary fiber and α-galactosyl derivatives of sucrose.  Major proteins are globulins and albumins.  The presence of various protease inhibitors, lectins, and lipoxygenase have been verified as well as flavonols, isoflavones, phenolic acids, tannins, and phytic acid.  Processing, soaking, and cooking may reduce the phytochemicals content and reduce nutritional content while also increasing the bioavailability of minerals and quality of proteins. 

Most beans are best planted around the average last frost date in the spring as they are sensitive to cold temperatures and frost.  The soil should be warmed to 60°F and begun to dry out.  One exception to this is peas, which need to be planted early enough in the spring so they mature while the weather is still cool.  Peas are usually planted between February and April in the United States and Canada and are grown as a fall or winter crop in warmer regions. Seeds should not be soaked in water although this is a popular myth as they can germinate poorly if they absorb too much water, either from soaking or from being planted in overly wet soil.  They are best watered after planting or planted before a heavy rain.  Seeds should be planted about one inch deep.  Bush beans can be planted four to six inches apart in rows two feet wide while pole beans should be planted three feet wide.  Ideal conditions will have full sun, well-drained soil, average fertility (too much fertility can produce excess foliage at the expense of the bean crop), slightly acidic soil with a pH from 6 to 6.8, and good air circulation.  Germination time under good conditions is typically eight to ten days.  Once the plant has germinated and emerges from the soil, it typically grows to a height of twelve to eighteen inches.  Successive crops are often planted every two to four weeks for an extended harvest season until late July in northern areas.  Hoeing must be done carefully as bean roots are shallow and brittle.  First-time plantings should have the soil inoculated with rhizobium bacteria, which invade plant root hairs and multiply while the plant produces a protective nodule enclosure and energy for the bacteria.  The bacteria converts nitrogen gas to ammonia in the nodules, which assists sprouting and may increase yield.  Monitoring for pests and diseases is important as well.   

Harvesting beans is a fairly simple process.  Most dry beans are harvested when they have lost a significant amount of moisture. Bush beans are ready for harvesting around fifty to sixty days after sowing while pole beans are ready for harvesting sixty to ninety days after sowing. Typically, farmers want to harvest beans when the pods are around 18% moisture. At this stage, the pods will be yellow and brown and not dry enough for the shells to shatter. Leaves will turn yellow and drop from the plant, leaving only stems and dry pods.   Green beans are best harvested when immature and pods that are bulging have grown past their peak.  Plants can be pulled up by hand or harvested by a combine, after which they are transported by truck to a storage bin or bean elevator. It is important to cut or snap beans from the plant and not tear pods from the branches.  If picked at the proper time, plants will continue flowering and produce new pods.  Beans that are properly dried before harvesting require minimal processing, need no refrigeration before freezing, and can be shipped all over the world.  Dry beans do require getting the beans out of the pods by threshing.  For small amounts, this can be done by hand by squeezing the pods open.  For more than a half-acre of beans, threshing equipment is used.  Cleaning and sorting is done after threshing and split beans are often fed to farm animals.  Different methods are used including sieves, sifters, destoners, gravity separators, and color sorters that use optical technology to separate beans by shape and color.  If the beans are to be canned, blanching is the first step in the process.  The beans are briefly scalded in boiling water, removed, and plunged into ice water or placed under cold running water.  This process is important to stop enzyme actions that can cause loss of flavor, color, and texture.  It also cleans the surface of dirt and organisms, brightens color, and helps stop the loss of vitamins.  After blanching, beans are sealed in cans with liquid (usually water), salt, and other additives that help maintain texture and color.  A pressure canner is used to cook the beans under high heat using steam pressure.  Canned beans do have a much higher sodium content than fresh beans and thorough rinsing and draining can reduce the sodium content by around forty percent.  Dry beans require much a longer cooking time but generally are higher in nutritional content and taste fresher, although the shelf-life of canned beans is usually a few years.  Processed beans are bean products that have been created from dried beans and imply that an additional step beyond conditioning has occurred.  Examples include baked beans, bean pastes, puffed snacks, refried beans, rehydrated beans, and bean flours.  Many types of beans and bean products can be found in fresh, canned, and processed forms and have become a staple food in most parts of the world.  

Beans and NIR Spectroscopy  

NIR spectroscopy has emerged as a tool for rapid, non-invasive, and cost-effective analysis of parameters of interest in beans that could potentially replace traditional reference methods.  There are a number of quality parameters in beans that have been studied and predicted with NIR spectroscopy with results suitable for process control purposes. Other parameters have shown results good enough for screening purposes and more study and calibration work could improve the prediction results.  Two comprehensive review papers have been published that examine the use of NIR spectroscopy in bean analysis.  The first examines various studies that used NIR spectroscopic applications to determine the feasibility of measuring quality parameters in faba bean crops, such as protein, moisture, starch, oil, tannins, alkaloid glycosides, and total polyphenols.  Discrimination analysis was studied as well, such as distinguishing different varieties and growing locations.  The study also reviewed some Mid-IR applications.  The second review paper examined NIR applications in different legumes, including faba bean, soybean, peas, and chickpeas. Parameters of interest include moisture, protein, fat, ash, fiber, lipids, starch, and carbohydrates.  Most studies examined in these two review papers showed good results.  Another study examined water content and germination time in mung bean, showing good correlation with reference methods and also providing a basis for correlating the ascorbic acid content to germination time.  Isoflavones are a key nutrient in soybeans and may help prevent osteoporosis.  NIR spectroscopy was examined for determining both individual and total isoflavone components, showing results good enough for screening purposes.  Cocoa beans are another important type of beans and NIR spectroscopy was used to determine fat and moisture content in another study.  Coffee beans are important as well and three studies using green coffee beans studied the feasibility of using NIR spectroscopy to determine moisture, caffeine, and chlorogenic acid in intact beans as well as sorting of Robusta beans.  NIR spectroscopy has also been used in practical applications to determine parameters like amino acid content in soybeans coming from different regions in Brazil and to determine protein content in faba beans in conjunction with mineral analysis by a different method to study the effects of growing location and genotype based on tannin content for studying potential genetic improvement to increase mineral content.  All these parameters and measurements have been studied using NIR spectroscopy with results showing the potential to replace traditional reference methods. 

References 

History of the Bean – Different Types of Beans 

http://www.vegetablefacts.net/vegetable-history/history-of-beans/ 

 18 Types of Beans 

https://www.jessicagavin.com/types-of-beans/ 

 Dry Beans Market – Growth, Trends, COVID-19 Impact, and Forecasts (2021-2026) 

https://www.mordorintelligence.com/industry-reports/dry-beans-market 

 Beans: The Basics 

https://www.medicalnewstoday.com/articles/320192#the-basics 

 What Are The Health Benefits of Beans? 

https://www.medicalnewstoday.com/articles/320192#the-basics 

 Nutritional and Bioactive Compounds of Bean: Benefits to Human Health 

https://pubs.acs.org/doi/pdf/10.1021/bk-2012-1109.ch015 

 Farm To Fork 

Farm-To-Fork.pdf (beaninstitute.com) 

 Beans Seed Germination, Time, Temperature, Process 

https://gardeningtips.in/beans-seed-germination-time-temperature-process 

 A Guide to Growing and Harvesting Dry Beans 

https://www.thespruce.com/grow-and-harvest-dry-beans-3016628 

 How Are Dried Beans Processed and Distributed Today? 

https://cablevey.com/how-are-dried-beans-processed-and-distributed-today/#:~:text=As%20for%20removing%20broken%20and,%2C%20destoners%2C%20and%20gravity%20separators.&text=This%20method%20involves%20blanching%20and,making%20them%20into%20a%20flour.