Sprouts, microgreens, and edible flowers: the potential for high value specialty produce in Asia

Abstract

Sprouts, microgreens, and edible flowers constitute a growing market segment in developed countries, where restaurant chefs use these plants and plant parts to add exotic flavors, colors and creative presentation to dishes offered to health-conscious, upscale consumers. Mungbean sprouts, and, to a lesser extent, soybean sprouts, which have been grown in Asia since ancient times, have now found their way into Western cuisine. Apart from pulses, cereals and oilseed crops, a number of vegetables and herbs are used for sprouting, including cress, mustard, snow peas, cabbage, kale, radish, spring onion, broccoli, basil, etc. Sprouts are usually densely packed in special sprouting cells and grown in high humidity and low light; such conditions favor the proliferation of dangerous bacteria that may cause severe food poisoning. Factors affecting seed and produce contamination as well as seed treatment measures for effective control of microbial growth are extensively discussed. In contrast to sprouts, microgreens are grown in soil or soil substitutes such as peat moss or other fibrous materials (cellulose pulp), and under light—and thus are less susceptible to contamination. Several crops or different varieties of the same crop can be mixed to create attractive combinations of textures, flavors, and colors. Edible flowers include ornamentals such as begonia, calendula, daylilies, hibiscus, and honeysuckle; fruit flowers such as banana and citrus blossoms; herb flowers such as angelica, borage, cilantro, fennel, ginger, jasmine, lemon verbena, marjoram, mint, rosemary, and safflower; and vegetable flowers such as alliums (leek, chives, garlic), arugula, artichoke, broccoli florets, okra, pak choi, pea, radish, scarlet runner beans, and squash blossoms. Many of these crops are indigenous to Southeast Asia, are quite popular, and can be grown inside homes, in kitchen gardens, or commercially. If properly promoted, microgreens could gain importance in Asia to diversify and enrich diets and add flavor, texture and color to dishes prepared at home or in fine dining restaurants.

Full text

Sprouts, microgreens, and edible flowers: the
potential for high value specialty produce in Asia
Ebert, A.W.
AVRDC – THE WORLD VEGETABLE CENTER, P.O. BOX 42, SHANHUA, TAINAN 74199, TAIWAN
andreas.ebert@worldveg.org
ABSTRACT
Sprouts, microgreens, and edible flowers constitute a growing market segment in developed
countries, where restaurant chefs use these plants and plant parts to add exotic flavors, colors
and creative presentation to dishes offered to health-conscious, upscale consumers. Mungbean
sprouts, and, to a lesser extent, soybean sprouts, which have been grown in Asia since ancient
times, have now found their way into Western cuisine. Apart from pulses, cereals and oilseed
crops, a number of vegetables and herbs are used for sprouting, including cress, mustard, snow
peas, cabbage, kale, radish, spring onion, broccoli, basil, etc. Sprouts are usually densely
packed in special sprouting cells and grown in high humidity and low light; such conditions
favor the proliferation of dangerous bacteria that may cause severe food poisoning. Factors
affecting seed and produce contamination as well as seed treatment measures for effective
control of microbial growth are extensively discussed. In contrast to sprouts, microgreens are
grown in soil or soil substitutes such as peat moss or other fibrous materials (cellulose pulp),
and under light—and thus are less susceptible to contamination. Several crops or different
varieties of the same crop can be mixed to create attractive combinations of textures, flavors,
and colors. Edible flowers include ornamentals such as begonia, calendula, daylilies, hibiscus,
and honeysuckle; fruit flowers such as banana and citrus blossoms; herb flowers such as
angelica, borage, cilantro, fennel, ginger, jasmine, lemon verbena, marjoram, mint, rosemary,
and safflower; and vegetable flowers such as alliums (leek, chives, garlic), arugula, artichoke,
broccoli florets, okra, pak choi, pea, radish, scarlet runner beans, and squash blossoms. Many of
these crops are indigenous to Southeast Asia, are quite popular, and can be grown inside
homes, in kitchen gardens, or commercially. If properly promoted, microgreens could gain
importance in Asia to diversify and enrich diets and add flavor, texture and color to dishes
prepared at home or in fine dining restaurants.
Keywords
High value specialty vegetables, sprouts, microgreens, edible flowers, Asia
INTRODUCTION
Population growth, the increased frequency of extreme weather events due to climate change,
high and volatile food prices and the on-going financial and economic crises make the
attainment of the Millennium Development Goal of reducing the proportion of people who
suffer from hunger by half by 2015 very unlikely. Increased investment in agriculture to
enhance productivity, sustainability and reduce vulnerability is seen as crucial to sustainable
long-term food security (FAO 2011). In addition to the lack of protein and energy intake from
staple foods, normally understood as hunger, malnutrition refers to the lack of micronutrients
and can be described as hidden hunger. Micronutrients are mainly derived from the
consumption of fruit and vegetables. Although malnutrition as measured by stunting has fallen
from 47% in 1980 to 33% in 2000, malnutrition of one out of three children below five years of
age remains a major concern in many developing countries (de Onis et al. 2000).
Geographically, about 70% of malnourished children live in Asia, 26% in Africa and four
percent in Latin America and the Caribbean.
A third form of malnutrition is caused by imbalanced diets due to overconsumption of
calories and poor food choices leading to obesity, type two diabetes and other chronicle
216 SEAVEG2012 Regional Symposium, 24-26 January 2012

diseases which are becoming an increasing burden in both developed and developing countries.
Mineral and vitamin deficiencies associated with malnutrition and chronicle diseases can be
best addressed with a diverse diet making use of pulses, fruit and vegetables (Yang et al. 2007;
Keatinge et al. 2011; Jamnadass et al. 2011).
To counter the ill effects of malnutrition and the negative impact of modern agriculture
and the food sector on the environment and climate, multiple initiatives are underway
worldwide to change current food production and consumption patterns, to enhance the
consumption of healthy and safe food and to promote more sustainable products and services.
An example of the multiple initiatives can be found in the ‘Roadmap to a Resource Efficient
Europe’ by 2050 (European Commission 2011).
Among those initiatives is the ‘Slow Food’ movement founded 1986 in Italy which
focuses on traditional and wholesome means of food production and defends biodiversity in
food supply. The current financial, environmental and energy crises are boosting this
movement which has activities in over 160 countries (The China Post 2011a). Just like AVRDC
– The World Vegetable Center is attributing a major role to school, community and disaster-
recovery gardens and other types of nutrition gardens to overcome malnutrition and to provide
better nutrition education, especially to the young generation (Keatinge et al. 2012), the ‘Slow
Food’ movement is implementing ‘A Thousand Gardens in Africa’ project to serve as source of
healthy food, to generate supplementary income and to demonstrate sustainable agriculture
(Slow Food Foundation 2011).
Due to health, ecological and religious concerns the number of vegetarians who abstain
from eating meat, fish, and poultry is growing. Vegans also abstain from consuming dairy
products and eggs and from using animal products such as silk, wool, and leather. According to
a recent poll undertaken by the Vegetarian Resource Group, approximately one-third of adults
in the U.S. are frequently eating vegetarian meals and five percent of the population are
vegetarians, out of which about half are vegans (Stahler 2011). With celebrities like actress
Katie Holmes, Alec Baldwin or even Bill Clinton frequenting upscale restaurants which only
serve vegan and raw food, the image of vegetarians and vegans is changing and is becoming
more mainstream (The China Post 2011b). Books are available trying to guide consumers
following this trend with raw food recipes for radiant health (Daniel and Daniel 2011).
Similar trends already existed in Europe as expressed in the ‘life reform movement’ which
started in Germany and Switzerland in the middle of the 19th century under the motto ‘back to
nature’ (Intentional Community Wiki 2011). This reform movement also included nutritional
reforms which emphasized the consumption of wholemeal bread and raw fruit and vegetables,
among others. During this same period the spread of vegetarianism began in Great Britain and
Germany. These trends have recently seen a revival and expansion in the haute cuisine.
Sprouts, microgreens and edible flowers are increasingly used by chefs to add exotic flavors,
colors and creative presentation to dishes offered to health-conscious, upscale consumers. This
paper describes the potential of this high value specialty produce for Asia.
Sprouts
Sprouts can be easily grown from a wide range of crop seeds, all year round, either at home or
on a large industrial scale. Untreated seeds of good quality and high germination rate are
washed, soaked in lukewarm water for 6 to 12 hours at room temperature. The seeds are then
densely packed into sprouting cells or vessels (glass jar, plastic pan) and covered with cheese
cloth or a greenhouse tent to maintain temperature and moisture (Meyerowitz 2010). The seeds
need to be rinsed or sprinkled several times per day to keep humidity high and facilitate
sprouting. Well, spring, or distilled water should be used for rinsing as chlorinated water may
result in poor sprouting (Bass and Sanders 1999). Sprouts take 5 to 14 days to mature,
depending on the crop (Meyerowitz 2010).
Crop groups used for sprouting are: (1) legumes (alfalfa, azuki bean, blackgram, chickpea,
lentil, mungbean, soybean); (2) cereals (barley, maize, oat, rice, rye, wheat); (3) pseudocereals
(amaranth, buckwheat, quinoa); (4) oilseeds (almond, hazelnut, linseed, sesame, sunflower);
and (5) vegetables and herbs (broccoli, cabbage, carrot, celery, clover, fennel, fenugreek, kale,
High Value Vegetables in Southeast Asia: Production, Supply and Demand 217

leek, lettuce, mustard, parsley, radish, rocket or arugula, snow and garden peas, spinach, spring
onion, turnip, watercress).
Among the bean sprouts, mungbean sprouts are the most common and most consumed
sprouts and are now found worldwide (Fig. 1). Mungbean, and, to a lesser extent, soybean
sprouts have long been a staple of Oriental and vegetarian diets. Soybean sprouts are known for
their appealing nutty taste and good texture (Shurtleff and Aoyagi 2007). They are produced
from special small-seeded soybean varieties and are the most popular sprouts in Korea. In
Japan, blackgram (Vigna mungo) is preferred as its sprouts are whiter and stay fresh for longer
than mungbean sprouts.
Mungbean sprouts are sold in market stalls in most of Asia, Central America and East
Africa and in recent years have also become quite popular in western countries where most
large supermarkets stock them. Mungbeans can be grown in about five days to 5 cm long
mature sprouts. Within eight days they can grow up to 8 to 9 cm long sprouts, but longer
growth above 10 cm should be avoided as sprouts then tend to become bitter (Bass and Sanders
1999). Mature sprouts are placed in a water-filled container for washing and removal of the
seed coats and fibrous roots. The sprouts will sink to the bottom and the seed hulls will float to
the top and can then easily be removed with a wire strainer. Sprouts are then allowed to drain.
Sprouts are best when consumed immediately after washing, but they can also be kept
inside closed glass and plastic containers or freezer bags for a few days up to one week in a
refrigerator. Sprouts can be eaten raw or cooked. The crispy sprouts are often added fresh to
appetizers, salads, soups, sandwiches and even desserts to add texture and flavor. Cereal
sprouts are also used in casseroles, pasta and baked products (Lorenz 1980). Sprouts can also
be canned or frozen if there is excess produce for fresh consumption, but this might lead to a
deterioration of their nutritional value.
Nutritional and health value of sprouts
Sprouts are commonly considered highly nutritious and are sometimes also called miracle food.
Soybean sprouts have the highest level of protein (28%) of all sprouts, followed by lentil and
pea sprouts with 26%. Soybean sprouts thus have twice the protein of eggs, but only 1/10th the
fat (Meyerowitz 2010). Due to respiration during the sprouting process, there is a loss in total
dry matter, an increase in total protein, a decrease in starch, an increase in sugars, and a slight
increase in some vitamins and minerals (Lorenz 1980). As total carbohydrates decrease during
germination, the percentage of other nutrients increases.
The flatulence-producing carbohydrates in legumes largely disappear during sprout
formation resulting in low levels of stachyose and raffinose (van Hofsten 1979). Due to the
biochemical changes during germination sprouts contain significantly higher levels of vitamins
than the respective dry seeds. Some sprouts such as mungbean are very good sources of
ascorbic acid reaching over 50 mg ascorbic acid/100 g fresh weight (van Hofsten 1979).
Vitamins of the B-group increase 100 to 300% during germination and sprouts are, therefore,
often a good source of vitamin B12. Moreover, phytic acid in the seed is degraded during
germination due to phytase enzyme activity resulting in higher availability of the trace minerals
compared to the dry seed (van Hofsten 1979).
Isoflavonoids, which protect against cancer, cardiovascular disease and osteoporosis are
found in relatively high concentration in soybeans, but their level is much lower in other
legume crops (Nakamura et al. 2001). The composition of isoflavonoids differs significantly
between soybean sprouts, immature beans and mature beans. The highest levels of
isoflavonoids in aglycone form - known to be of stronger biological activity than the glycoside
form – are found in soybean sprouts and progressively decrease from sprouts via immature
beans to mature beans, the latter having the lowest levels. The percentage of the glucoside form
of isoflavonoids increases in reverse order.
Rocket or arugula (Eruca sativa Mill.) is a popular cruciferous vegetable which is found
worldwide and is known for its typical spicy taste. It is usually consumed fresh in the form of
leaves or sprouts. It is highly nutritious and contains a range of health-promoting ingredients
such as carotenoids, vitamin C, fibers, flavonoids, and glucosinolates. Specific research on
rocket revealed direct antioxidant activity of purified glucoerucin, a major glucosinolate found
218 SEAVEG2012 Regional Symposium, 24-26 January 2012

in rocket seeds and sprouts (Barillari et al. 2005). Glucosinolates are the precursors of
isothiocyanates, which are released through the enzyme myrosinase during cutting, chewing, or
processing of this vegetable. Isothiacyanates have been identified as potent inducers of phase II
enzymes which are involved in the detoxification of electrophiles and protect against oxidative
stress. The glucosinolate glucoerucin comprises 95% of total glucosinolates in rocket seeds.
This content is largely preserved in sprouts (79% of total glucosinolates), but to a much lesser
extent in adult leaves (Barillari et al. 2005).
The health-promoting effect of cruciferous (and legume) sprouts was confirmed in a
human diet study conducted by Gill and co-workers (2004). These researchers found a
significant antigenotoxic effect against H2O2-induced DNA damage in peripheral blood
lymphocytes of volunteers who were fed 113 g of cruciferous and legume sprouts daily for 14
days compared to the group fed with the control diet. The consumption of cruciferous
vegetables can thus be linked to a reduced risk of cancer.
Earlier feeding studies with rats supported the cancer preventing effect of cruciferous
vegetables. Deng and co-workers (1998) studied the effects of Brussels sprouts, some non-
cruciferous vegetables and isolated glucosinolates on spontaneous and induced oxidative DNA
damage in male rats. A short oral administration of 3g of cooked Brussels sprouts homogenate
for only four days significantly reduced the spontaneous urinary 8-oxodG excretion by 31% as
opposed to raw sprouts, beans and endive and isolated indolyl glucosinolates which did not
have a significant effect. Cooking of Brussels sprouts appears to activate substances which
have the potential to reduce physiological as well as oxidative stress induced oxidative DNA
damage.
Studies on broccoli, another cruciferous vegetable, revealed that broccoli sprouts contain
on a gram-fresh-weight basis up to 50 times more glucoraphanin, the glucosinolate precursor of
sulforaphane compared with mature broccoli plants (Fahey et al. 1997; Fahey and Stephenson
1999; Fahey et al. 2001). Sulforaphane is the most potent natural phase II enzyme-inducer
known. Extracts of 3-day old broccoli sprouts were highly effective in reducing the incidence
and rate of development of mammary tumors in rats (Fahey et al. 1997).
Broccoli sprouts also contain negligible or no detectable amounts of the indole and β-
hydroxyalkenyl glucosinolates that predominate in the mature vegetable and may give rise to
degradation products (e.g., indole-3-carbinol) that can enhance tumorigenesis (Fahey et al.
1997; Shapiro et al. 2001). The latter authors concluded that myrosinase activity in intact
broccoli sprouts contribute significantly to the bioavailability of isothiocyanates by boosting
the glucosinolate-to-isothiocyanate conversion. Dithiocarbamate excretion was clearly
enhanced when fresh sprouts were chewed thoroughly rather than swallowed whole.
Isothiocyanates are about six times more bioavailable than glucosinolates (Shapiro et al. 2001).
Thorough chewing facilitates hydrolysis by releasing myrosinase and glucosinolates from their
sequestered sites within the plant cells (Barillari et al. 2005).
Dietary alfalfa administration (Medicago sativa L.), a leguminous vegetable, led to
reduced serum or plasma cholesterol in several experimental animal species, such as rats,
rabbits, and monkeys. Cholesterol-saponin interactions have been postulated as mechanisms for
the hypocholesterolemic effects of alfalfa (Story et al. 1984). These researchers demonstrated
that alfalfa plant saponins bind significant quantities of cholesterol. Alfalfa sprout saponins also
interacted significantly with cholesterol, but to a lesser extent than mature plants.
To ensure microbial safety of fruits and vegetables, irradiation is one of several measures
that have been proposed. When alfalfa sprouts were irradiated with gamma rays and stored at
6 oC for 14 days, this had only a minimal effect on total ascorbic acid (TAA) content when
compared with the decrease of TAA during storage (Fan and Thayer 2001). However,
antioxidant power increased linearly with radiation dose at one and seven days of storage and
carotenoid content of sprouts was also enhanced at higher radiation doses compared to control
sprouts at seven days of storage.
Health concerns associated with the consumption of sprouts
Sprouts are usually densely packed in special sprouting cells and grown in high humidity and
low light; such conditions favor the proliferation of dangerous bacteria that may cause severe
High Value Vegetables in Southeast Asia: Production, Supply and Demand 219

food poisoning. Documented outbreaks of food poisoning in humans linked with the
consumption of raw fruits, vegetables and unpasteurized juices have substantially increased in
the United States in the recent past (DeRoever 1998; Buck et al. 2003).
This may be partially attributable to enhanced epidemiologic and surveillance techniques
which are now at the disposal of public health agencies which allow disease outbreaks to be
linked with the probable source of infectious microorganisms (Burnett and Beuchat 2001).
Other contributing factors are changes in dietary habits which include a higher per capita
consumption of fresh or minimally processed fruits and vegetables, and the increased use of
salad bars and meals eaten away from home (Altekruse and Swerdlow 1996). Especially in
industrialized countries consumers have become much more health-conscious and want to
maintain a healthier diet and thus eat much more raw fruit and vegetables. The year-round
availability of high-quality fresh produce due to globalization contributes to this trend.
Other factors which may have contributed to a higher frequency of foodborne illness
outbreaks associated with the consumption of raw fruits and vegetables are changes in
production and processing methods, new sources of produce and the emergence of pathogens
previously not associated with raw produce (Hedberg et al. 1994).
The danger of widespread outbreaks of foodborne illness became evident in 1996 in Japan
where more than 6000 Escherichia coli infections were reported (Guiterrez 1997). Raw radish
sprouts prepared in central school kitchens appear to have transmitted the pathogen leading to
four deaths and 4000 ill school children in and around Sakai City, the center of the outbreak. In
the U.S. nine outbreaks of foodborne illness were reported between 1995 and 1998 which could
be traced to the consumption of fresh vegetable sprouts (NACMCF 1999). In most of these
cases, alfalfa or clover seed were identified as the initial inoculum source. Other sprout-related
disease outbreaks have been reported in Japan, Great Britain, Finland, Denmark, Sweden, and
Canada which could be traced to alfalfa, cress, radish, and mungbean sprouts (Puohiniemi et al.
1997; Taormina et al. 1999; Taylor et al. 2002).
The most recent and perhaps most dramatic outbreak of gastroenteritis and the hemolytic-
uremic syndrome caused by a shiga-toxin producing E. coli strain in Germany in May/June
2011 has also been linked to sprout consumption implicating an organic sprout farm in Lower
Saxony near Hamburg as the potential pathogen source (Frank et al. 2011; Kuijper et al. 2011).
A total of 3816 cases including 54 deaths were reported during this outbreak, 845 of which
involved the hemolytic-uremic syndrome (Frank et al. 2011).
Sources of contamination and measures to avoid contamination
In many cases, the seeds used for sprout production are considered as significant inoculum
source for foodborne illnesses associated with sprout consumption (NACMCF 1999; Taormina
et al. 1999). However, due to the common practice of blending seedlots, the original source of
contaminated seed can often not be determined (Mahon et al. 1997). During the production of
seeds intended for sprouting, the practice of animal grazing to initiate flowering in alfalfa may
result in the unintentional introduction of enteric bacteria from feces into the seed production
field (Buck et al. 2003). The same may happen if wild animals have access to seed fields.
Manure used as fertilizer or soil amendment should be properly treated to eliminate pathogenic
microorganisms and animals should be excluded from sprout seed production fields. Irrigation
wells and water used for irrigation should be monitored for the presence of human pathogens.
There are also many factors which may introduce contamination during post-harvest
operations. Such factors include human handling, harvesting and processing equipment,
transport containers and vehicles, wild and domestic animals having access to the produce,
insects, dust, rinse water, and ice (Burnett and Beuchat 2001).
Small initial populations of pathogens can reach high numbers during sprout production
thanks to favorable conditions of high relative humidity and temperature, together with
nutrient-rich root exudates (Prokopowich and Blank 1991). Pathogenic bacteria easily survive
for prolonged periods in or on stored dried seed and survival is enhanced at lower temperatures
in seed storage (Taormina and Beuchat 1999). Physical seed damage during seed processing
may also enhance bacterial survival and cross-contamination.
220 SEAVEG2012 Regional Symposium, 24-26 January 2012

Conventional methods to eliminate human pathogens from fresh produce
Washing and rinsing fruits and vegetables is perhaps the easiest way to partially reduce the
number of microorganisms on the surface and thus prolong shelf life (Burnett and Beuchat
2001). The addition of disinfectants to wash water enhances the efficacy of decontamination by
up to 100-fold (Beuchat 1998). However, pathogens differ in their sensitivity to sanitizers.
There are also mechanical barriers in fruit and vegetable structures and tissues harboring
pathogens that render sanitizers ineffective.
Pathogenic bacteria may infiltrate protected areas of produce such as cracks and
intercellular spaces of seeds and fruit or vegetable surfaces (Buck et al. 2003). Pathogen
infiltration into plant tissues depends on temperature, time of exposure and pressure and occurs
only when water pressure on the surface of the produce exceeds internal gas pressure as well as
the hydrophobic nature of the surface of the produce (Burnett and Beuchat 2001; Beuchat
2002). Bacterial infiltration is enhanced by the presence of surfactants and with produce
temperatures higher than the temperature of the water suspension harboring the pathogen.
Growth of microorganisms in such protected areas of produce can result in the formation of
biofilms that are difficult for sanitizers to penetrate (Carmichael et al. 1999).
Seed treatment
The reduction of microbial contamination can be more easily achieved by sanitizing seeds,
rather than sprouts. To reduce the risks of sprout-borne illnesses, chemical or physical seed
treatments are routinely applied. Chemical seed treatments for sprout seeds include chlorine
compounds (calcium and sodium hypochlorite), ethanol, hydrogen peroxide, calcium EDTA,
ozonated water, and commercial disinfectants (Beuchat 1997, 1998; Beuchat et al. 2001; Lang
et al. 2000; Taormina and Beuchat 1999; Weissinger and Beuchat 2000). Seed used for
sprouting can also be treated with gaseous chemicals (Delaquis et al. 1999; Weissinger et al.
2001).
While chlorine compounds are still widely used in the fresh-cut industry for disinfection
purposes, there is growing public health concern about the formation of chlorinated organic
compounds such as chloramines and trihalomethanes that are linked to a higher rate of cancer
in humans. The emergence of new, more tolerant pathogens also calls for alternative treatment
options (Singh et al. 2002). Moreover, the prolonged exposure to chlorine vapors may lead to
irritation of the skin and respiratory tract of workers (Beuchat 1999). In many European
countries the application of chlorine or other disinfectants is not allowed for the production of
organic food (Bari et al. 2011). In response to these concerns, acidic electrolyzed water, a novel
non-thermal food sanitizer has been developed in Japan which has strong bactericidal and
virucidal and moderate fungicidal properties (Issa-Zacharia et al. 2010).
Hot water treatment has also been explored for seed disinfection (Grondeau and Samson
1994). Seeds are, in general, exposed for about 10 min to 57 to 60oC. While hot water will kill
seedborne bacteria, there might be a negative impact on seed germination and sprout vigor. In
Japan, hot water treatment at 85oC for 40 seconds followed by cooling in cold water for 30
seconds and soaking in chlorine water is currently still considered as safe and effective
treatment to inactivate pathogens on mungbean seeds intended for sprout production without
compromising seed viability, germination and vigor (Bari et al. 2011). However, consumers in
Japan are advised to consume sprouts only after cooking. When used for salads, mungbean and
soybean sprouts should be dipped in boiling water for about 10 seconds to minimize the risk of
foodborne illnesses.
With large seed batches it is difficult to maintain uniform temperature within the water
bath and this method is thus of little practical value for commercial application. Combinations
of thermotherapy with chlorine resulted in the reduction, but not complete elimination, of
Salmonella (Jaquette et al. 1996) and E. coli O157:H7 (Beuchat and Scouten 2002) populations
on alfalfa seeds.
Gamma radiation has been successfully tested for the elimination of E. coli and
Salmonella from seeds intended for sprouting, without affecting seed germination (Rajkowski
and Thayer 2000) and is commonly used for food preservation (Farkas 2006). Radiation energy
is an attractive treatment for seeds as it can penetrate seed tissues and eliminate bacteria located
in protected tissues (Buck et al. 2003). However, high levels of radiation can negatively affect
High Value Vegetables in Southeast Asia: Production, Supply and Demand 221

the physiology of sprouts, hence more research is needed to establish the potential and risks of
this treatment. Other non-thermal approaches for reducing foodborne pathogens include super-
critical carbon dioxide (Mazzoni et al. 2001), ultraviolet radiation, ultrasound treatments
(Scouten and Beuchat 2002) and magnetic resonance fields.
The complete elimination of bacteria on seeds is difficult to achieve for two major reasons:
(1) treatment dosage must not harm seed viability and might, thus, be suboptimal for complete
disinfection; (2) to be effective, sanitizers must fully reach the pathogens which might be
located in protected seed tissues. Greater success may be achieved by combining compatible
seed treatments without compromising seed viability or physiology (Buck et al. 2003). This
approach to inhibit the growth of microorganisms in produce is known as hurdle technology in
food preservation (Leistner 2000; Zhang 2007). In this approach, suitable combinations of
microbe growth-limiting factors (hurdles) such as temperature (high or low), water activity
(aw), acidity (pH), redox potential (Eh), preservatives, and competitive microorganisms (e.g.
lactic acid bacteria) are applied to ensure microbial safety and stability as well as the sensory
and nutritional quality of the produce or food product.
Microgreens
Just like sprouts, microgreens are grown from the seeds of a wide range of crops such as
vegetables, herbs and other plants. Microgreens are defined as salad crop shoots harvested for
consumption within 10-20 days of seedling emergence (Lee et al. 2004). They are larger than
sprouts, but are smaller than ‘baby’ greens. Microgreens have a central stem with two fully
developed cotyledon leaves and mostly one pair of small true leaves.
Commonly grown microgreens include amaranth, basil, beet, cabbage, celery, chervil,
Chinese kale, cilantro, fennel, garden cress, mustard, parsley, radish, rocket or arugula, snow
pea, sorrel, and Swiss chard.
Unlike sprouts, microgreens are not grown in water, but in soil or soil substitutes such as
peat moss or other fibrous materials (cellulose pulp), and under light—and thus are less
susceptible to bacterial contamination. Although wood or paper fiber mulches have a lower cost
than peat-lite as growth media for microgreens, the latter was found superior for beet, rocket
and amaranth microgreens (Murphy 2006). Insufficient nutrient levels, low cation exchange
capacity, and excessive liquid retention leading to inadequate aeration are factors that might
have contributed to reduced growth of microgreens on mulches compared with peat-lite. The
production of beet microgreens in troughs using the hydroponic nutrient film technique (NFT)
resulted in higher shoot fresh weight per m2 than production in trays containing peat-lite
(Murphy et al. 2010). Maximum shoot fresh weight was obtained using beet seed balls pre-
germinated in moist vermiculite followed by subsequent growth in troughs with NFT.
As microgreens are in contact with soil or soil substrates, they are prone to pre- and post-
emergence damping-off caused by soilborne pathogenic fungi. Due to the very short pre-
harvest period biological control of damping-off is preferred over chemical treatments for the
safe production of microgreens. The combination of Trichoderma harzianum (Th) and T. virens
(Tv) strains was successfully used to control damping-off in beet microgreens (Pill at al. 2011).
Increased levels of ThTv to beet seed balls or growth media resulted in a decreased incidence of
damping-off with concomitant increase in shoot fresh weight per m2 at 14 days after planting
which is attributable to an increased percentage of plant survival.
Microgreens are usually grown in high light conditions with low humidity and good air
circulation. The seed density is much lower than with sprouts. Therefore, microgreens have
much better developed flavors and taste than sprouts and are an ideal component of any meal,
adding a broad range of leaf shapes, textures, color and distinct flavors (Fig. 2). In addition,
several varieties of the same crop or different crops can be grown together to create attractive
combinations of tastes, textures, and colors. These mixtures are available commercially and are
known as ‘mesclun’ (Franks and Richardson 2009).
Just like sprouts, microgreens can easily be grown at home, in containers on a terrace or
windowsill. Popular guides to growing microgreens are available for the hobby gardener, along
with information on their nutritional value, ideas on how to use them, and recipes (Franks and
Richardson 2009; Hill 2011).
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Microgreens are increasingly used as a fresh flavor accent in fine dining restaurants where
creative presentation, fresh appearance, and distinct flavor elements are expected from the
upscale customers. There are a number of commercial microgreen growers catering to this new
dining trend. Companies usually briefly describe the special flavors and taste of each product
and make suggestions for dishes to which these microgreens can best be added to. Lines used to
grow these microgreens are a trade secret and often patented. Many of the lines commercially
grown have been sourced in Asia and most likely have not undergone major breeding efforts,
but might rather have been obtained from a wild or semi-domesticated state to guarantee its
original richness in flavors and taste.
Edible flowers
Edible flowers which greatly differ in shape, color and taste stimulate not only the eyes, but
also other senses like taste and smell. From east to west and since ancient times, flowers have
not only been used for decoration and aesthetic appearance, but as relishes and flavor enhancers
for many savory dishes, salads (Fig. 2) and desserts as well. Capers, the flower buds of
Capparis spinosa L. have been used as condiment in Europe for over 2000 years (Smythe
2011). A variety of edible flowers such as roses, elder flowers, and hawthorn blossoms were
used in the Anglo-Norman cuisine during the 13th and 14th century. The flowers of calendula
were used for the preparation of salads in medieval France (Mlcek and Rop 2011). During the
Victorian era in the 19th century edible flowers were also very popular and often used as part of
salads (Smythe 2011).
During the past 15 to 20 years, edible flowers have seen a revival, both in haute cuisine as
well as in home-cooked meals. Flowers are served as a garnish and/or as edible component of
soups, savory dishes, and cold buffet food and petals are used to decorate salads, desserts, and
drinks. In addition to the aesthetic appearance, flowers have also to correspond with the
specific taste and smell of a creative dish. For example, flowers of borage, acacia or roses serve
as aromatic enhancers of pastry (Mlcek and Rop 2011).
In some countries, edible flowers are now being promoted as a healthy food. The Thai
Health Promotion Foundation has initiated a campaign under the name ‘Food Safety: Edible
Flowers” promoting a range of dishes and drinks containing edible flowers
(Wongwattanasathien et al. 2010).
Edible flowers can be marketed fresh, dried, sugarcoated, in bulk, as singles or by weight
and offer good opportunities for small-scale enterprises (Handwerker et al. 1990). They include
ornamentals such as begonia, calendula, daylilies, hibiscus, chrysanthemum, dianthus,
dandelion, geranium, garden nasturtium, pansy, rose, honeysuckle, and blue violets; fruit
flowers such as banana, citrus, and elderberry blossoms; herb flowers such as angelica, basil,
borage, cilantro, fennel, ginger, jasmine, lemon verbena, marjoram, mint, rosemary, sage, and
safflower; and vegetable flowers such as alliums (leek, chives, garlic), arugula, artichoke,
broccoli florets, okra, pak choi, pea, radish, scarlet runner beans, okra, pumpkin and squash
blossoms.
For consumption as food, edible flowers should be obtained from a reliable source,
preferably from organic production to ensure that they are free from pesticide residues. Flowers
should be thoroughly washed before use as food. It is preferable to introduce flowers only in
small quantities and one species at a time into the diet to avoid problems with the digestive
system. It is usually recommended to remove stamens and styles from the flowers before
eating. Although pollen is a rich source of proteins, amino acids and carbohydrates, carotenoids
and flavonoids (Mlcek and Rop 2011), it is not recommended to eat the pollen as it may detract
from the distinct flavor of the flowers and may cause allergic reactions.
Edible flowers are either eaten whole or parts thereof, such as petals of tulips,
chrysanthemums or roses (Mlcek and Rop 2011). When only the petals are eaten, they should
be separated from the rest of the flower just prior to use to minimize wilting. For some edible
flowers like roses, it is necessary to remove the basal part of the petals as these parts are bitter.
In the case of cucurbits, baby squashes with attached blossoms are now standard in the upscale
restaurant trade (Schneider 2001). The squash flowers are amenable to stuffing which can
High Value Vegetables in Southeast Asia: Production, Supply and Demand 223

easily be done with a pastry tube. When prepared in a microwave, the color and crunch of the
baby squashes and the form of the filled pouches is maintained.
Perceived sensory characteristics such as attractive appearance, size, shape, taste, aroma
and coloring are the most important quality criteria of edible flowers, apart from their
freshness. In general, consumers prefer yellow and orange colors; blue and combinations of
other colors are liked less (Kelley et al. 2001, 2002).
Flowers are quite delicate and sensitive and prone to microbial decay if not carefully
handled. After picking, they should be immediately placed into plastic (zip-lock) bags and/or
other containers which provide protection against contamination and wilting. Plastic bags must
be perforated to prevent condensation of vapors on their inner surface. Harvested flowers are
quickly cooled and cleaned and can then be stored at a temperature of 1-4oC for a period of 2
up to 14 days (Kelley et al. 2003). Picking time is also important for some crops. Squash
blossoms, for example, should be collected in the early morning as they will wilt on the vine by
late morning (Schneider 2001). Once picked at the right time, squash blossoms stay fresh for a
few days in the refrigerator. Compounds with antioxidant activity are very important for the
keeping quality of flowers as these substances delay the process of senescence and decay which
is caused by the action of reactive oxygen radicals on biomembranes (Panavas and Rubinstein
1998).
Multiple uses have been reported for a range of native and non-native Hibiscus species in
the U.S. (Puckhaber et al. 2002). Whole fresh, dehydrated or freeze-dried or frozen petals can
be used as edible flowers in the restaurant business, for use in nutraceutical products and
specialty gourmet foods due to their relatively high levels of flavonoid aglycones, and for the
extraction of natural food colorants for applications in the food and beverage industry. Other
potential applications for fresh and processed Hibiscus blossoms are the formulation of skin-
care products or cellulosic and mucilaginous dietary products (Puckhaber et al. 2002).
Many edible flowers have chemoprotective effects as they are rich sources of phenolic
compounds, carotenoids and flavonoids with high antioxidant and free radical suppressing
properties (Kaisoon et al. 2011; Mlcek and Rop 2011) or have curative medicinal effects.
Friedman and co-workers (2007) highlighted the antioxidant activity in flowers of begonias,
roses or garden nasturtiums and Que and co-workers (2007) observed a strong scavenging
activity of reactive oxygen radicals and lipid peroxidation in extracts of daylily. The
antioxidant activity of stored flowers seems to be quite stable as even after one week of cold
storage their values did not change much. This is attributed to the high content of gallic acid,
one of the essential antioxidants occurring in edible flowers (Anesini and Perez 1993).
Rojanapo and Tepsuwan (1992) attributed antimutagenic activity to some vegetable
flowers like neem (Azadirachta indica A. Juss., sesbania (Sesbania grandiflora (L.) Pers.), and
cassia (Senna siamea (Lam.) H.S. Irwin & Barneby). Methanol extracts of turmeric (Curcuma
sessilis Gage) and pomegranate (Punica granatum L.) flowers also revealed high antimutagenic
effects (Wongwattanasathien et al. 2010).
CONCLUSION
Many of the crops used to grow sprouts, microgreens or edible flowers around the world are
indigenous to Asia or have been introduced to Asia. They are widely known and at least
partially used in the Oriental cuisine. These crops can easily be grown inside homes, in kitchen
gardens, or commercially. If properly promoted and safely produced, packaged and served,
sprouts, microgreens and edible flowers could gain growing importance in Asia. They are an
attractive component to diversify and enrich diets and add flavor, texture and color to dishes
prepared at home or in fine dining restaurants.
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Figure 1. Commercial mungbean sprout production.
Figure 2. Microgreens and edible flowers enhancing a salad
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