The South African government sees agriculture and the processing of agricultural products as a promising avenue for creating jobs and boosting the economy. It is investing in research projects to get farmers in South Africa interested in growing emerging products such as honeybush, a plant used to make a sweet, floral, honeylike tasting tea. But when it comes to more established products, such as wine, industry provides the lion’s share of R&D money, with the government kicking in a small amount of funds.
From dark, velvety pinotage to fruity, lip-puckering chenin blanc, South African wine is growing in popularity worldwide. The industry takes quality seriously and, along with the government, is investing in scientific research to find out what tastes and aromas consumers prefer.
At Stellenbosch University’s Institute for Wine Biotechnology, in the heart of South Africa’s wine-growing region, researchers are integrating chemical profiling of wine with analysis of the way such chemicals affect the sensory characteristics. Then they add consumer research to get a better handle on what people like to drink. So far they have studied fewer than 100 of the 1,000 or so chemicals found in wine.
Chemical profiling is like taking a fingerprint of the wine, explains Hélène H. Nieuwoudt, a spectroscopist at the institute. Using gas and liquid chromatography, mass spectrometry, and infrared spectroscopy, she and her colleagues measure the major volatile chemicals in wines, showing everything from the indirect effects of soil conditions to seasonal variations.
Such profiling is extremely useful to verify the authenticity of wine, says Nieuwoudt. “You can verify the wine-making technique. If the wine was matured in wood, you can actually see that on the fingerprint,” she notes.
Chemical profiling is also conducted on grapes that are still on the vine to monitor ripening or diseases. Nieuwoudt and colleagues are developing nondestructive methods for measuring critical parameters in the vineyard, including sugar content and the organic acid profile of grapes.
Such information is used to determine the optimal time to harvest grapes, without having to taste or destroy any grapes. Once grapes have been picked, chemical profiling is also used to evaluate their quality and determine whether they will be used to make premium quality wine, a blend, or bulk wine, Nieuwoudt says.
Chemicals in wine can be divided into compounds originating from the grapes, such as monoterpenes; fermentation-derived compounds, such as alcohols, esters, and fatty acids; and compounds formed during the aging or maturation process, such as volatile phenols and oak lactones, says Andreas G. J. Tredoux, an analytical chemist at the institute.
For example, sauvignon blanc has an asparagus or green pepper taste that has been attributed to a monoterpene originating in the grapes, and chenin blanc has a tropical, guavalike taste. The chemical that is responsible for the guava flavor has yet to be identified, but Tredoux and colleagues suspect it is a volatile thiol compound.
Terpenes and related compounds in grapes are bound to sugars. During the wine-making process, those bonds are broken. Once terpenes are free from sugar they have a quite intense aroma, Tredoux says.
Fermentation-derived compounds include ethanol, methanol, propanol, butanol, esters, and fatty acids—all of which are in equilibrium. That equilibrium shifts with changes in acidity, leading to changes in the amount of each compound in the wine. Numerous factors beyond pH also affect fermentation-derived compounds, including the type of yeast, the fermentation temperature, and the contact time with the yeast after fermentation is complete, Tredoux notes.
During the final phase of wine making, wine is often aged in a wooden barrel or wood chips are added, particularly to red wine. The wood produces compounds such as whisky lactone and vanillin, giving wine a roasty characteristic.
Once the researchers obtain the chemical profile of a wine, they combine the information with sensory characteristics determined by a panel of trained people. “We train human panels to act as instruments,” Nieuwoudt says. The panel identifies flavors and aromas, such as fruitiness or berry, and determines whether the intensity is strong or weak. The panel also looks at the visual appearance of the wine. The goal, after some statistical analysis, is to determine how the chemistry influences the sensory characteristics.
Ultimately, of course, winemakers want to know how those characteristics influence consumer preference. For chenin blanc, for instance, female consumers aged 20 to 34 seem to prefer a more fruity style and males prefer a more complex, less fruity style. “Ultimately you want to keep the consumer happy,” Tredoux says. “Our job is to figure out what it is chemically that they don’t like, so the winemaker can decide, for example, ‘Let’s use this yeast strain and not that one.’ ”
Wine is a fairly large export product for South Africa. The country is ranked eighth in the world in terms of wine production and 12th in terms of surface area devoted to wine production. With only a limited area that is suitable for growing grapes, primarily in the Western Cape, South Africa is known for the quality of its wines more than the quantity.
Another growing, albeit small, export product for South Africa is rooibos tea, and more recently, honeybush tea. The rooibos plant is indigenous to the Western Cape, but today it is primarily cultivated on plantations in the Cederberg area of South Africa near Clanwilliam. Honeybush tea is a nascent market compared with rooibos tea. Although some research is being done on cultivating honeybush, it is primarily harvested from the wild in the natural shrubland called the fynbos throughout the Western and Eastern Capes.
Both rooibos and honeybush teas are gaining popularity. They are known for their antioxidant and immune-boosting properties, and neither one contains caffeine. Research into the beneficial health effects, flavor identification, and quality aspects of rooibos and honeybush teas has been funded by both the South African government and the tea industry.
Government scientists at the Agricultural Research Council (ARC), the primary agricultural research institute in South Africa, have taken a lead role in honeybush tea research. One of their goals is to develop new products, such as dietary supplements and cosmetics, using extracts from the plants. They are also focusing on improving the quality of the teas and training farmers how to cultivate the plants.
“We must understand the chemistry of the plant to develop new products or to improve the quality,” says Lizette Joubert, a chemist with ARC’s Postharvest & Wine Technology division in Stellenbosch. Joubert worked with rooibos tea as a Ph.D. student and began focusing on honeybush processing in 1993.
Today, Joubert is particularly excited about a chemical in honeybush called mangiferin, a xanthonoid also found in mangoes and mango tree bark. Mangiferin has been shown to have antimicrobial, antioxidant, and antidiabetic properties. Mangiferin content is quite high in at least two species of honeybush, Joubert says. She is hoping to produce a mangiferin-rich extract from honeybush because it is more renewable than mango tree bark, she says.
Joubert is also interested in extracting hesperidin from honeybush. Hesperidin is a flavanone glycoside found in citrus fruit. The compound is known for its antioxidant and anti-inflammatory properties.
Over the past 20 years, much of Joubert’s research has focused on improving the quality of honeybush tea. When she first began working with honeybush, “the quality was horrendous,” she tells C&EN. “People had fermentation heaps, but it was like making compost,” she recalls.
Joubert studied the effects of fermentation time and temperature on honeybush tea quality and helped the industry develop a standard process. Today, honeybush tea is sold in more than 25 countries. Demand for honeybush is outpacing supply.
Part of the reason for the low supply is that the majority of honeybush is still harvested from the wild, but efforts are under way to cultivate the plant. Joubert and her colleague, Marlise Joubert, no relation, have been working with various communities in the Eastern and Western Capes to help farmers get started growing honeybush.
One project, for example, was carried out over three years in the town of Genadendal in the Western Cape, where the people often harvest honeybush from the wild for themselves. The researchers established a demonstration plot to determine whether a particular species of honeybush can grow there and then trained the local people. At the end of the project, some of them wanted to carry on because they saw the potential to bring in some income, Lizette says.
The biggest hurdle is a lack of tea-processing facilities, Lizette notes. “This is the major thing I see that is keeping the industry back,” she tells C&EN. “Processing is expensive, and not all farmers want to do it themselves. But if you don’t have a processing plant near you, transport costs become prohibitive,” she says.
So far, a few communities of farmers are cultivating honeybush, but it is very slow going, Marlise tells C&EN. The crop is attractive to farmers because it is a legume and therefore fixes its own nitrogen. Farmers don’t need to add nitrogen fertilizer, and the amount of phosphorus required is low. In addition, honeybush is perennial and can survive up to eight years.
Most honeybush is grown without pesticides. The biggest threat is not insects or deer, says Cecilia Bester, a senior researcher in plant breeding and genetics at ARC. “People are actually our biggest problem,” she points out. As the demand for honeybush grows, more and more poachers are stealing it from private and public lands. Although a permit is required to harvest honeybush, Bester says, many people are doing it illegally.
Serikali ya Afrika Kusini inaona kilimo na usindikaji wa bidhaa za kilimo kama njia ya kuahidi kwa ajili ya kuunda ajira na kuongeza uchumi. Msaada wa utafiti wa kiuchumi wa Afrika Kusini kwa wakulima wa kusini unaonyesha kuwa kuna uwezekano mkubwa wa kuzalisha matunda ya asali, ambayo ni aina ya chai ya asali. Lakini linapokuja bidhaa zilizowekwa zaidi, kama vile divai, sekta hutoa sehemu ya simba ya fedha za R&D, na serikali inatoa kiasi kidogo cha fedha. Kutoka pinotage nyeusi, yenye rangi ya velvety hadi chenin blanc yenye matunda, yenye kuvutia midomo, divai ya Afrika Kusini inazidi kupendwa ulimwenguni pote. Viwanda vinachukua ubora kwa uzito na, pamoja na serikali, wanawekeza katika utafiti wa kisayansi ili kujua ni ladha na harufu gani zinazopendwa na watumiaji. Chuo Kikuu cha Stellenbosch cha Ufundi wa Mvinyo, katika moyo wa eneo la uzalishaji wa divai la Afrika Kusini, watafiti wanaunganisha maelezo ya kemikali ya divai na uchambuzi wa jinsi kemikali hizo zinavyoathiri sifa za hisia. Kisha wanaongeza utafiti wa watumiaji ili kupata ufahamu bora juu ya kile watu wanapenda kunywa. Kwa sasa, wanasayansi hawajachunguza kemikali 100 kati ya 1,000 zinazopatikana katika divai. "Kuchunguza kwa njia ya kemikali ni kama kuchukua alama ya kidole cha divai,"" anaeleza Hélène H. Nieuwoudt, mtaalamu wa uchunguzi wa rangi katika taasisi hiyo." Kwa kutumia chromatography ya gesi na kioevu, spectrometry ya wingi, na spectroscopy ya infrared, yeye na wenzake hupima kemikali kuu za mvuke katika divai, kuonyesha kila kitu kutoka kwa athari za moja kwa moja za hali ya udongo hadi mabadiliko ya msimu. Utafiti huo ni muhimu sana kuthibitisha uhalisi wa divai, anasema Nieuwoudt. <unk>Unaweza kuthibitisha mbinu ya kutengeneza divai. Kama mvinyo ilikuwa kukomaa katika mbao, unaweza kweli kuona kwamba juu ya alama ya kidole, <unk> yeye anasema. Uchunguzi wa kemikali pia hufanywa kwenye zabibu ambazo bado ziko kwenye mzabibu ili kufuatilia kukomaa au magonjwa. Nieuwoldt na wenzake wanaendeleza mbinu zisizo na uharibifu za kupima vigezo muhimu katika shamba la mizabibu, ikiwa ni pamoja na maudhui ya sukari na wasifu wa asidi ya kikaboni ya zabibu. Habari hizo hutumiwa kuamua wakati mzuri wa kuvuna zabibu, bila kuhitaji kuonja au kuharibu zabibu zozote. "Kama zabibu zimechaguliwa, ""profiling ya kemikali pia hutumiwa kutathmini ubora wao na kuamua kama watatumiwa kutengeneza divai ya ubora wa juu, mchanganyiko, au divai ya wingi,"" anasema Nieuwwoudt." "Kama ilivyoelezwa, ""kitu ambacho hufanyizwa wakati wa kuzaa ni kemikali zinazotokana na zabibu, kama vile monoterpenes, kemikali zinazotokana na fermentation, kama vile alkoholi, esters, na asidi za mafuta, na kemikali zinazotokana na mchakato wa kuzeeka au kukomaa, kama vile phenol na lactones ya mwaloni,"" anasema Andreas G. J. Tredoux, mtaalamu wa kemia ya uchambuzi katika Taasisi hiyo." Sauvignon blanc ina ladha ya asparagus au pilipili ya kijani ambayo imesababishwa na monoterpene inayotokana na zabibu, na chenin blanc ina ladha ya kitropiki, kama guava. Kemia inayosababisha ladha ya guava bado haijulikani, lakini Tredoux na wenzake wanashuku ni kiwanja cha thiol chenye kuteleza. Terpenes na misombo inayohusiana katika zabibu huunganishwa na sukari. Wakati wa utengenezaji wa divai, vifungo hivyo huvunjwa. Mara tu terpenes zinapokuwa huru kutoka kwa sukari huwa na harufu kali sana, Tredoux anasema. Misombo inayotokana na uchemchemi ni pamoja na ethanol, methanol, propanol, butanol, esters, na asidi za mafuta - zote ambazo ziko katika usawa. Mabadiliko hayo ya asidi huathiri kiasi cha kila kiwanja katika divai. Vitu vingi zaidi ya pH pia huathiri misombo inayotokana na uchemchemi, ikiwa ni pamoja na aina ya chachu, joto la uchemchemi, na muda wa kuwasiliana na chachu baada ya uchemchemi kukamilika, Tredoux anasema. Katika hatua ya mwisho ya utengenezaji wa divai, divai mara nyingi huchukuliwa katika pipa la mbao au vipande vya mbao huongezwa, hasa kwa divai nyekundu. Mbao hiyo hutokeza kemikali kama vile lactone ya wiski na vanillin, ambazo hutoa mvinyo sifa ya kuoka. Baada ya watafiti kupata sifa za kemikali za divai, wanaunganisha habari hizo na sifa za hisia zinazotambuliwa na kikundi cha watu waliozoezwa. "Tunawazoeza paneli za kibinadamu kutenda kama vyombo", Nieuwoudt anasema. Jopo hilo hutambua ladha na harufu, kama vile matunda au matunda, na kuamua ikiwa nguvu ni kali au dhaifu. Jopo hilo pia huchunguza jinsi divai hiyo inavyoonekana. Lengo, baada ya uchambuzi fulani wa takwimu, ni kuamua jinsi kemia inavyoathiri sifa za hisi. Kwa kweli, hatimaye, watengenezaji wa divai wanataka kujua jinsi sifa hizo zinavyoathiri mapendezi ya watumiaji. Kwa mfano, kwa ajili ya chenin blanc, watumiaji wa wanawake wenye umri wa miaka 20 hadi 34 wanaonekana kupendelea mtindo wa matunda zaidi na wanaume wanapendelea mtindo tata zaidi, wa matunda kidogo. "Hatimaye unataka kuweka watumiaji furaha",Tredoux anasema. <unk>Jukumu letu ni kugundua ni nini kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa kimetengenezwa Nchi hiyo iko katika nafasi ya nane duniani kwa uzalishaji wa divai na ya kumi na mbili kwa eneo la ardhi lililotumiwa kwa uzalishaji wa divai. Kwa kuwa eneo lake ni dogo sana kwa ajili ya kukuza zabibu, hasa katika Western Cape, Afrika Kusini inajulikana kwa ubora wa divai zake zaidi ya wingi. Bidhaa nyingine inayokua, ingawa ni ndogo, inayouzwa nje ya Afrika Kusini ni chai ya rooibos, na hivi karibuni, chai ya honeybush. Mti wa rooibos ni asili ya Western Cape, lakini leo hupandwa hasa katika mashamba katika eneo la Cederberg la Afrika Kusini karibu na Clanwilliam. Chai ya Honeybush ni soko linalopanda ukuzi ikilinganishwa na chai ya rooibos. Ingawa kuna utafiti fulani unaofanywa kuhusu kulima honeybush, hasa huvunwa katika mazingira ya asili ya misitu inayoitwa fynbos katika maeneo yote ya Western na Eastern Capes. Chai za rooibos na za honeybush zinapendwa sana. Mazao hayo yanajulikana kwa sababu ya uwezo wake wa kuzuia vimeng'enya na kuimarisha mfumo wa kinga, na hakuna hata moja kati ya hayo yenye kafeini. Utafiti kuhusu athari zenye manufaa kwa afya, utambulisho wa ladha, na mambo ya ubora wa chai za rooibos na honeybush umefadhiliwa na serikali ya Afrika Kusini na sekta ya chai. Wanasayansi wa serikali katika Baraza la Utafiti wa Kilimo (ARC), taasisi ya msingi ya utafiti wa kilimo nchini Afrika Kusini, wamechukua jukumu la kuongoza katika utafiti wa chai ya honeybush. Mojawapo ya malengo yao ni kutengeneza bidhaa mpya, kama vile virutubisho vya chakula na vipodozi, kwa kutumia vichwa vya mimea hiyo. Pia wanakazia kuboresha ubora wa chai na kuwafundisha wakulima jinsi ya kulima mimea hiyo. "Ni lazima tuelewe kemia ya mmea ili kuendeleza bidhaa mpya au kuboresha ubora, "anasema Lizette Joubert, mtaalamu wa kemia na ARC's Postharvest & Wine Technology division huko Stellenbosch. Joubert alifanya kazi na chai ya rooibos kama mwanafunzi wa PhD na alianza kuzingatia usindikaji wa honeybush mnamo 1993. "Jubert anaamini kwamba kuna kemikali inayoitwa ""mangiferin"" ambayo pia hupatikana katika mango na magamba ya miti ya mango." Mangiferin imeonyeshwa kuwa na mali ya kupambana na vimelea, antioxidant, na antidiabetic. Joubert anasema kwamba angalau spishi mbili za miti ya asali zina kiasi kikubwa cha mangiferin. "Mwanamke huyo anasema kwamba ana matumaini ya kutengeneza dawa ya ""mangiferin"" kutokana na mti wa asali, kwa sababu ni mbadala wa mti wa mango." Joubert pia anapendezwa na kutokeza hesperidin kutoka kwa mti wa asali. Hesperidin ni glycoside ya flavanone inayopatikana katika matunda ya machungwa. Kiwanja hicho kinajulikana kwa sababu ya uwezo wake wa kuzuia na kuzuia uvimbe. Katika miaka ya hivi karibuni, utafiti wa Joubert umekuwa ukielekezwa kwa kuboresha ubora wa chai ya honeybush. Alipoanza kufanya kazi na honeybush, "ubora ulikuwa mbaya sana", anaambia C&EN. "Watu walikuwa na rundo la kuyeyusha, lakini ilikuwa kama kutengeneza mbolea", anakumbuka. Joubert alichunguza athari za wakati wa kuchemka na joto juu ya ubora wa chai ya honeybush na kusaidia sekta hiyo kuendeleza mchakato wa kawaida. Leo, chai ya honeybush inauzwa katika nchi zaidi ya 25. Mahitaji ya miti ya asali yanazidi ugavi. Sehemu ya sababu ya upatikanaji mdogo ni kwamba wengi wa honeybush bado ni kuvunwa kutoka porini, lakini juhudi zinaendelea kulima mmea. Joubert na mwenzake, Marlize Joubert, ambao hawana uhusiano wowote, wamekuwa wakifanya kazi na jamii mbalimbali katika Eastern na Western Capes kusaidia wakulima kuanza kukuza honeybush. Kwa mfano, mradi mmoja ulifanywa kwa miaka mitatu katika mji wa Genadendal katika Western Cape, ambako watu mara nyingi hukusanya misonobari ya asali kutoka porini kwa ajili yao wenyewe. Watafiti walianzisha eneo la maonyesho ili kujua ikiwa aina fulani ya mti wa asali inaweza kukua huko na kisha kuwazoeza watu wa eneo hilo. "Lazy alisema, ""Wakati wa mradi huo, baadhi ya wanafunzi waliamua kuendelea na mradi huo kwa sababu waliona uwezekano wa kupata mapato." Lizette anasema kwamba tatizo kubwa ni ukosefu wa vifaa vya kutengeneza chai. "Hii ni jambo kuu naona kwamba ni kuweka sekta nyuma", yeye anaambia C&EN. <unk>Utaratibu ni ghali, na si wakulima wote wanataka kufanya hivyo wenyewe. Lakini ikiwa huna kiwanda cha usindikaji karibu nawe, gharama za usafirishaji huwa ngumu, "anasema. Kwa sasa, jamii chache za wakulima zinazalisha misonobari, lakini ni polepole sana, Marlise anaambia C&EN. Mazao hayo yanavutia wakulima kwa sababu ni mboga na kwa hiyo huhifadhi nitrojeni yake mwenyewe. Wakulima hawana haja ya kuongeza mbolea ya nitrojeni, na kiasi cha fosforasi kinachohitajika ni cha chini. Kwa kuongezea, mti wa asali ni wa kudumu na unaweza kuishi hadi miaka minane. Miti mingi ya asali hukua bila dawa za kuua wadudu. "Hata hivyo, kuna uwezekano mkubwa kwamba mnyama huyo ni mnyama wa aina ya ""Cecilia"" Bester, ambaye ni mtafiti wa mimea na urithi wa ARC." "Watu kwa kweli ni tatizo letu kubwa zaidi", yeye anasema. Kadiri mahitaji ya misonobari ya asali yanavyoongezeka, ndivyo wawindaji wengi wanavyoiba misonobari hiyo kutoka kwenye mashamba ya kibinafsi na ya umma. Ingawa inahitajika kibali cha kuvuna miti ya asali, Bester anasema kwamba watu wengi hufanya hivyo kinyume cha sheria.