Tea Safety – What are the Key Areas of Food Safety in Tea Manufacturing - I

Tea as a Beverage

This series of articles trying to explain about the product specific food safety concerns and preventive actions. The idea is to help readers understand product specific and process specific hazards as well as their impact on food safety. Thus entire series will not come at once but it will take some time to complete most of the widely spread categories of products in the market.

As usual, the beverage industry can be considered as one of the largest in terms of quantity of sales, where tea (Camellia sinensis) was initially considered as a medicine and later grew into a beverage which is the second most favourite drink after water and it is the most consumed manufactured drink in the world.

According to the Chinese legends, tea was first discovered in the time Second Emperor and herbalist, Shennong in 2737 B.C.E, accidently; when a dried tea leaf was fallen into the boiling water which is intended for emperor’s thirst while he was travelling to another region (Chow & Kramer, 1990), who drank boil water as a habit. In the time of Han Dynasty (206 BCE – 220 CE), tea was used as a medicine and much later tea became popular as a beverage and people started drinking it in social events at Tang Dynasty around 618 – 2907 CE (Berggreen, 2014) and it is one of the oldest beverages in the world today.

In seventeenth centaury, tea was introduced to the west where it became quickly popular due to the flavour and simulative properties extracted to boiling water (Wright, 2005) because of the cold climatic conditions hot water drinking was a habit in those societies and due to the poor hygiene of water during this era, boiling of water was common place. In fact, first tea consignments were reached in London in 1652, where there were hygiene threats due to the lots of water born diseases as a result of industrialization and pollution of urban water courses. Thus people used to drink boiled water which has no fresh taste where addition of tea gave it both flavour and taste due to the presence of caffeine (UK Tea and Infusions Association, 2015). Even though coffee and chocolate also introduced in to the Europe in same era, both of them were unaffordable for the general public until after second world war and other alternative was alcohol which also kill the pathogens, but it was not practical solution where tea became more popular than other beverages (Wright, 2005). Tea even became a seed for wars, such as the opium war in China (1840 – 1842) which irreversibly changed the entire cultures with positive and negative effects.   Today, it is a multimillion dollar industry with over USD 4 billion revenue and growing while employing more than 15 million people globally and providing over four billion tea cups a day all over the world (A Fairtrade Foundation, 2010). In addition, current research findings on the health aspects of tea drinking also prove that the first assumptions of drinking tea as a medicine is true all along the history as it assumed by Chinese people without proper evaluations (Wright, 2005).

Modern commercial tea plantations are being cultivated longitudes between 42° N (Russia) and 27° S (Argentina), while altitudes starting from the mean sea level zero from up to 2200 m. tea plant has wide adaptability which grows in a range of different climates and soils in several parts of the world. Tea also can adapt different rain shower patterns at different annul precipitation levels with the minimum annual rainfall considered necessary for the successful cultivation of tea is 1,200 mm, while the optimum ranges between 2,500 and 3,000 mm. Rainfall must have to be evenly distributed year-round to get an optimum yield with an annual average temperature around 18-20°C which is usually ideal for the tea bush. In addition, the soil type must be deep, well drained and exhaustively aerated, nutritious red-yellow soil with a low pH (4.5-6.5) where extended drought periods, water logging conditions and temperatures below 12°C and above 30°C are not favourable for the growth of tea (Williges 2004). The slope must not be too steep and the maximum tolerable gradient is 25 degrees.

Tea as a beverage spread throughout Asia from China which soon became the national beverage of China and Japan, but until the 1600s the Europeans didn’t became familiar with the beverage. In the early 1900s, tea was just introduced to the North America where Thomas Sullivan, a New York wholesaler, decided to package tea in small silk bags rather than in tins. Thus people started brewing the tea in the silk bag rather than removing its contents where the tea bag was born and first introduced. Today it is available for consumption in six main varieties, based on the oxidization and fermentation technique applied.

Today, there are wide variety of tea products exist in the market such as instant tea, iced tea mixes, specialty and flavoured teas, herbal teas, ready-to-drink teas decaffeinated teas and tea bags. The packaging of tea products has changed significantly where most of the small shops that once dispensed tea from wooden crates into individual tins have given way to sophisticated high-speed production lines which process, package, and/or bottle thousands of pounds of tea and ready-to-drink mixes per hour.   

Processing

There are different types of processing methods, but four major types in the market according to the processing type which are white, green, olong and black teas. However, these four types have many different sub categories due to the way of manufacturing, i.e. orthodox back tea, CTC (cut; tear; curled) tea, rotavane orthodox black tea etc. Tea is usually received in wooden crates or large bags, which is blended and packed in packaging machines, where it is packaged either as individual tea bags or in bulk packages. Instant powdered tea requires blended tea in fine particle form to be brewed using hot water, which is concentrated and then spray dried into a fine powder and aseptically packed to avoid moisture absorption.  The powder may be packaged into canisters or jars, or blended with other ingredients such as sugar or sugar substitutes, where flavours may also be added during the blending stage prior to packaging.

Potential Food Safety Hazards

Tea is a beverage prepared by infusing the dry tea leaf in water in most cases, boiling water is used but cold water can be used particularly when preparing ‘iced tea’. Thus manufacturing process is one of the most important areas to be considered when considering the food safety hazards where it is important to consider each and every step in the manufacturing process for hazard assessment. Following potential food safety hazards were identified from primary production and processing of tea up to the packaging.

Chemical contamination

Physical contamination - foreign matter

Microbiological contamination

The hazard analysis needs to be applied according to the food safety system specific to customer requirements which is based on HACCP principles by tea manufacturer to each specific processing operation separately in order to conduct a hazard analysis and to consider any measures to control identified hazards.

Chemical Contamination

The critical limits for chemical contamination are those given in EU and national legislation 3, 4, 5 and 10 which is the most common guideline applicable, but manufacturer can adapt to national legislation of the exporting country or manufacturing country. Because national guidelines sometimes differ from EU legislation but EU specified limits are more stringent, which should take precedence regardless of whether these legislative limits apply to the producing country or the country of sale. Further to that, absence of a legal limit does not preclude individual packers setting limits for additional contaminants in line with their company policies.

As a general norm, no naturally occurring constituents of tea have been identified which are likely to present a safety risk requiring control measures, but chemical contamination can happen because of environmental pollution, inappropriate use of agrochemicals, sabotage, adulteration, lubricants from tea processing machinery, fumigant residues from the fumigation of containers and contamination during transport or storage.  Additionally, environmental pollution may result in enhanced levels of heavy metals from a variety of sources, e.g. nearby industry, traffic on nearby roads.

However, the available literature and in-house monitoring by European tea packers clearly demonstrates that the incidence of high levels of heavy metal contamination is low with the levels found rarely exceeding the limit values and hence heavy metals present a minimal food safety risk.

Agrochemicals may be present because of the use of non-approved chemicals or their use without adherence to Good Agricultural Practice (GAP) where the monitoring of ‘pesticide’ residues by the trade shows that for most origins, values exceeding the current legal maximum residue levels (MRLs) are infrequent and at levels which do not compromise food safety. In some origins, residues exceeding the MRLs values are detected and in these instances the teas are not purchased as to do so would be illegal. As a result, the food safety risk from agrochemicals is considered to be low.

The polycyclic aromatic hydrocarbon (PAH) content of most teas when brewed is below the limit of detection of current analytical methodology, but some analysis has occasionally shown low levels in tea leaves as evidenced by trade summaries of in-house generated data. Some teas, notably Lapsang Souchong, are ‘smoked’ as part of their processing and contain measurable levels of PAHs; given that most of the PAHs present are relatively insoluble in water and as a consequence their levels in the infusion as consumed are much reduced it is considered that they present a minimal food safety risk.

Toxic substances can be present as a result of accidental or deliberate contamination where there were few warnings that some teas have been deliberately contaminated in the country of origin. There were two such instances in last ten years and despite intensive checks both at source and by the packers on receipt, no contamination has been found. Given that warnings have been issued when deliberate contamination has been threatened and the fact no contamination has been found it is considered that the risk of chemical contamination by deliberate contamination is low.

Chemical contamination resulting from lubricants, fumigation of containers, transport and storage are known but occur infrequently and thus presents a low risk in food safety terms. Chemical contamination could also result from inappropriate personal behaviour which might contaminate food, for example smoking when handling harvested tea leafs and tea (packaged or unpackaged).

Instances of adulteration are rare and traditionally tea quality is assessed by tea tasters who base their judgements on subjective assessments of the leaf before and after infusion and the appearance, odour and taste of the liquor, rather than by reference to its chemical composition. The chemical testing is done only if the taster is not satisfied on his subjective testing and requested for a test. However certain chemical characteristics have been defined and given in ISO 2037 International Standard, which is helpful if the tea exhibits abnormal characteristics or adulteration is suspected.

But if you want to find most stringent food safety and quality standards, which is go beyond private standard usually does is Product Certification Scheme for Tea (PCST). The PCST was born because, there were lots of rejects and consumer complaints on Ceylon Tea, where SLTB took control the situation with its dictatorship over the industry due to government interests on the product. The SLTB and SLS jointly introduce a product certification scheme to certify the manufacturing process and the final product, i.e. Black Tea where the scheme was based on applicable standards of  SLSI; Sri Lanka Standard SLS 135:2009; Specifications for black tea and ISO 3720:1986; Black tea- Definition and basic requirement as well as applicable SLTB regulations. The scheme called SLSI – SLTB: Product Certification Scheme for Tea (PCST) which was designed to meet the specific requirements of the tea plantation sector while providing internationally recognized third party compliance to consumers.  SLSI - SLTB Product Certification for Tea (PCST) is therefore comprehensive and it includes the following;

1. Applicable Tea Board Regulations & Sri Lanka Tea Board Standards/ Guidelines for Sri Lankan Origin Tea.
2. Sri Lanka Standard SLS 135:2009; Specifications for black tea and ISO 3720:1986; Black tea- Definition
3. Industry related code of Practices: SLS 1315: 2007; Code of practice for Tea Industry - Part 1& Part 2.

The given scheme was essentially voluntary in nature where it is largely based on ISO/ IEC Guide 65: 1996; General requirements for bodies operating product certification systems. The ISO/ IEC Guide 65: 1996 provides general rules for third party certification of determining with standards through initial testing and assessment of a factory quality management system and its acceptance followed by surveillance that takes into account the factory quality management system (QMS) and the testing of sample from the factory and the open market (slsi.lk).