Chapter 5 Other Beverage Ingredients PDF

## Chapter 5 Other Beverage Ingredients ### 5.5.5 High Alkalinity This is due to the presence of bicarbonates, carbonates and hydroxides of the alkaline earth and alkali metals – principally, calcium, magnesium, sodium and potassium. The effect of high alkalinity is to buffer acidity in a soft drin...

## Chapter 5 Other Beverage Ingredients ### 5.5.5 High Alkalinity This is due to the presence of bicarbonates, carbonates and hydroxides of the alkaline earth and alkali metals – principally, calcium, magnesium, sodium and potassium. The effect of high alkalinity is to buffer acidity in a soft drink, with the creation of a bland taste. It is essential, therefore, to maintain a consistent alkalinity level, and the majority of manufacturers aim for below 50 mg/l as CaCO₃. Alkalinity may be reduced by coagulation treatment or by ion exchange. ### 5.5.5.4 Nitrates With modern methods of intensive farming, in which nitrate-based fertilisers are employed, there has been a noticeable increase in nitrate levels from aquifers lying beneath agricultural land. The recommended limit for nitrate has been given as 50 mg/l by the World Health Organisation (WHO). The health risk of nitrates involves a condition seen in infants known as methaemoglobinaemia. ### 5.6 Acidulents The use of acidulents is an essential part of beverage formulation. Acidulents perform a variety of functions in addition to their primary thirst-quenching properties, which are the result of stimulating the flow of saliva in the mouth. Because it reduces pH, the acidulent can act as a mild preservative and, in some respects, as a flavour enhancer, depending on the other components present. Most importantly, however, reduction of the product pH to below 4.5, and mostly 4.4, eliminates risk of the presence of pathogens. In addition, by functioning as a synergist to antioxidants such as BHA (butylated hydroxy anisole), BHT (butylated hydroxy toluene) and ascorbic acid, acidulents can indirectly prevent discolouration and rancidity. In carbonated beverages, there is the additional effect of dissolved carbon dioxide gas. Although it is not officially recognised as an acidulent, the inclusion of carbon dioxide, under pressure, will certainly provide extra sparkle, mouth-feel, flavour and sharpness in a drink. Its inclusion may require the rebalancing of the amount of acidulent added. **Table 5.2 Acidulants used in beverages formulations** | Acidulant | Molecular Weight | Melting point (°C) | |---|---|---| | Citric acid, 2-hydroxy-1,2,3-propane tricarboxylic acid HOOCCH₂C(OH)(COOH)CH₂COOH | 192.1 | 152-154| | Tartaric acid (D-tartaric) 2,3-dihydroxy butanedioicacid HOOCCH(OH)CH(OH)COOH| 150.1 | 171-174| | Phosphoric acid orthophosphoric acid H3PO4 | 98.0 | 42.35| | Lactic acid (DL-lactic) 2-hydroxy propanoic acid CH₃CH(OH)COOH | 90.1 | 18| | Malic acid (D-malic) 2-hydroxy butandioic acid HOOCCH(OH)CH₂COOH | 134.1 | 98-102| | Fumaric acid trans-butenedioic acid HOOCCH=CHCOOH | 116.1 | 299-300| | Acetic acid ethanoic acid CH₃COOH | 60.0| 16-18| ### 5.6.1 Citric Acid Citric acid is the most widely used acid in fruit-flavoured beverages. It has a light, fruity character that blends well with most fruit flavours, which is to be expected, as it occurs naturally in many fruit types. Unripe lemons contain 5-8% citric acid. It is also the principal acidic constituent of currants, cranberries and others, and is associated with malic acid in apples, apricots, blueberries, cherries, gooseberries, loganberries, peaches, plums, pears, strawberries and raspberries. It is associated with isocitric acid in blackberries and tartaric acid in grapes. ### 5.6.2 Tartaric Acid Tartaric acid occurs naturally in grapes, where it is present as the acid potassium salt. During the fermentation of grapes, tartaric acid precipitates from solution as crystals, as its solubility decreases with the increasing alcoholic concentration of the wine. Tartaric acid is also a natural component of numerous other fruits, such as the currants, blackberries and cranberries. Tartaric acid can be obtained in four forms: dextro, laevo, meso and the mixed-isomer equilibrium, or racemic, form. Commercially, it is usually available as dextro-tartaric acid. This acid has a sharper flavour than citric and it may, therefore, be used at a slightly lower level to give equivalent palate acidity (see Table 5.3). Tartaric acid can be isolated from the crude deposit of tartrates obtained during wine fermentations, in a similar manner to that used for citric acid - that is, by leaching the deposit with boiling hydrochloric acid solution, filtering it and re-precipitating the tartrates as the calcium salt. The free acid is obtained by treatment of calcium tartrate with sulphuric acid and further purification by crystallisation. **Table 5.3 Palate acidity equivalents.** | Acidulent | Concentration (g/l) | |---|---| | Acetic | 1.00 | | Ascorbic | 3.00 | | Citric | 1.22 | | Fumaric| 1.08| | Lactic | 1.36| | Malic | 1.12| | Phosphoric | 0.85| | Tartaric | 1.00| Note: These concentrations, in water, are considered to be equivalent (tartness, sourness) from taste trials carried out in the laboratories of Borthwicks Flavours (now Danisco (UK) Ltd.), Wellingborough in 1990. Although subjective, they give a proximate comparison of the pure acid effect in solution. ### 5.6.3 Phosphoric Acid Phosphoric acid is the only inorganic acid to be widely used in food preparations as an acidulent. It does, however, occur naturally in the form of phosphates in some fruits, including limes and grapes. In the soft drinks industry, its use is confined almost entirely to cola-flavoured carbonated beverages, where its special type of 'astringent' acidity complements the dry, sometimes balsamic, character of cola drinks. Phosphoric acid has a drier, and perhaps sharper, flavour than either citric or tartaric acids, tasting, rather, of flat 'sourness', in contrast with the sharp fruitiness of citric acid. It therefore appears to blend better with most non-fruit drinks. Pure phosphoric acid is a colourless crystalline solid (m.p. 42.35°C), and it is usually employed in solution as a strong, syrupy liquid, miscible in all proportions with water. It is commercially available in solution concentrations of 75%, 80% and 90%. The syrupy nature of its solution occurs at concentrations greater than 50%, and is the result of hydrogen bonding between the phosphoric acid molecules. Phosphoric acid is corrosive to most construction materials, so rubber-lined steel or food-grade stainless steel holding vessels are generally recommended. ### 5.6.4 Lactic Acid Lactic acid is one of the most widely distributed acids in nature, and it is used to a great extent by the food industry. Its use in beverages, however, is limited. It has a mild taste relative to the other acids, and is used in soft drinks as a flavour modifier or enhancer, rather than as an acidulent. Lactic acid is supplied commercially as an odourless and colourless viscous liquid. It is produced via the fermentation of carbohydrates such as corn, potato or rice starch, cane or beet sugar, or beet molasses, using lactic acid bacteria. ### 5.6.5 Acetic Acid Acetic acid has a very limited use in beverages, only finding use where its vinegary character can contribute to a suitable flavour balance in the intended product. It is seldom used in anything except non-fruit beverages. Pure glacial acetic acid is a colourless crystalline solid (m.p. 16°C), with a suffocating, pungent aroma. It is one of the strongest of the organic acids, in terms of its dissociation constant, and it can displace carbonic acid from carbonates. ### 5.6.6 Malic Acid Occurring widely in nature, malic acid is closely associated with apples. It is the second major acid, after citric acid, found in citrus fruits, and it is present in most berry fruits. Malic acid is slightly stronger than citric acid in perceived acidity, imparting a fuller, smoother fruity flavour. Malic acid is a crystalline white solid (m.p. 100°C) that is highly soluble in water. Being less hygroscopic than citric acid, it provides good storage and shelf-life properties. Unlike tartaric acid, its calcium and magnesium salts are highly soluble, so therefore it presents no problem in hard water areas. The acid finds use in a variety of products, mostly in fruit-flavoured carbonates. It is the preferred acidulent in low-calorie drinks, and in cider and apple drinks, enhancing flavour and stabilising colour in carbonated and non-carbonated fruit-flavoured drinks. Malic acid may also be used to mask the off-taste of some sugar substitutes. Blends of malic and citric acids are said to exhibit better taste characteristics than either acidulent individually. ### 5.6.7 Fumaric Acid This is not permitted under UK or European legislation for direct use in soft drinks, although it is permitted, under Annex IV of Directive 95/2/EC (modified by directive 98/72/EC), with strict limits, in instant powders for fruit, tea or herbal-based drinks. Fumaric acid finds wide use in other countries as an acidulent, notably in the US market, where it has GRAS status. Fumaric acid is currently manufactured in the US via the acid-catalysed isomerisation of maleic acid. In terms of equivalent palate acidity, it can be used at lower levels than citric acid, and typical replacement is suggested at two parts fumaric per three parts citric in water, sugar water and carbonated sugar water. The main drawback in the use of fumaric acid is its slow solubility rate compared with citric acid, and special methods need to be employed in its dissolution. It is claimed that fumaric acid and its salts have a tendency to stabilise the suspended matter in both flash-pasteurised and frozen fruit concentrates (McColloch and Gentile, 1958). ### 5.6.8 Ascorbic Acid This acid, known more familiarly as Vitamin C, is sometimes used as a contributory acidulent, but also as a stabiliser within the soft drinks system, and its antioxidant properties serve to improve the shelf-life stability of flavour components. Many of the ingredients used in flavourings are susceptible to oxidation – particularly aldehydes, ketones and keto-esters. Ascorbic acid shields these from attack by becoming preferentially oxidised and lost, leaving the flavour component unaffected. It should be noted that, although ascorbic acid acts well as a browning inhibitor in unprocessed fruit juices, its effect can be destroyed, should the juice be subsequently pasteurised or heat-treated. In such cases, ascorbic acid can initiate its own chemical browning reaction. Another disadvantage of ascorbic acid is its effect on some colours in the presence of light. In the case of azo-colours, such as carmoisine, a light-catalysed reaction occurs, resulting in cleavage of the -N=N- linkage and consequent destruction of the chromophore. This accounts for the disappearance of colour, and bleaching of the characteristic hue associated with some soft drinks. ### 5.7 Flavourings It is the flavour of a drink that provides not only a generic identity, but also a unique character. This part of the sensory profile is responsible for pleasing and attracting the consumer. For example, having decided on a cola drink, the consumer will be able to differentiate between colas by virtue of the background flavouring components, which collectively provide a reference point to which the consumer can return, consciously or not, on future occasions, whenever a particular brand of drink is tried. <start_of_image> Areas to consider: * What is a flavouring * What is a flavour blend * What are the techniques of getting information about flavours * Why flavour profiles need to be compared * How and why we need analytical support A flavouring consists of a mixture of aromatic substances that are carefully balanced to convey the right message to the sensory receptors of the consumer. The preparation of such a mixture is a serious matter; the flavourist, like the perfumer, must be well versed in the technique, be creative and be able to translate ideas into a practical solution. While it is often difficult for the consumer to communicate descriptions of what is being tasted, the flavourist has no such limitations. The flavourist approaches the subject in a professional manner, and is seldom at a loss when describing organoleptic attributes, as a personal library of stored knowledge relating to flavouring substances and types can be called upon. For example, some descriptors that might be applied to a peach-flavoured drink are: * Sweet * Juicy * Fruity * Lactonic * Astringent * Acidic * Skinny * Floral * Estery * Aldehydic * Ripe * Fresh * Stewed * Jammy * Perfumed Depending on the desired profile, the flavourist may add to, or subtract from, a central theme until an acceptable blend is reached. Although the art of the flavourist depends largely on individual sensory abilities, it is frequently necessary in present-day flavour work to enlist analytical support at an early stage of the project. Modern instrumental analytical techniques are capable of detection at extremely low levels, but it is still usually necessary to prepare an extract, or concentrated version, of the target flavour before carrying out the analysis. This may be achieved by solvent extraction, distillation, adsorption chromatography, dialysis, headspace concentration and cryogenic or adsorbent trapping, among other methods. A good gas chromatographic/mass spectrophotometric (GC/MS) system can be used to identify profiles of compounds and individual flavouring substances up to, say, 98% of the target flavour, thus by-passing much of the time-consuming preliminary work associated with organoleptic flavour matching. GC/MS can provide an extremely rapid and reliable assessment, leading to a tolerable flavour match that requires only slight 'tuning' adjustments for completion of the work. In the creation of a flavouring, there is inevitably a level of comparison against what is already accepted as the generic base. Thus, a strawberry flavour is at once typical, to a marked degree, of the fruit itself; however, on a commercial level, the characterisation of this base flavour into something new will set it apart from the competition and will lead to success in the market. Descriptors such as 'fresh', 'cooked', 'jammy', 'green', 'wild', 'ripe', 'full-bodied', 'creamy', 'estery', 'sweet', 'artificial', 'natural' and many others may be applied in the assessment, as the taster searches for an adjective that best describes what is being conveyed via neurological pathways from taste sensors to brain. At best, the subjective nature of such an assessment will move into a common acceptable pathway across a wide number of tasters. It is at this point that the flavour may be identified as a winner although, even now, success will depend upon the type of application, marketing strategies, and so on. ### 5.7.1 Flavourings and Legislation Food ingredients in general have been well investigated in terms of use and effect, categorised, and registered under permitted lists as appropriate to local legislation around the world. Flavourings, because of their complexity, have always existed as a separate group when considered as food ingredients, and they are subject to a whole section of legislation in their own right. This legislation, as one might expect, is subject to variation from country to country, and global harmonisation is yet to be completely realised. * **Codex Alimentarius:** is a collection of internationally recognised guidelines relating to food safety, codes of practice and food standards, and it forms a basis for food legislation in many countries. It is recognised by the World Trade Organisation as a reference point for disputes relating to food safety and consumer protection. The Codex Alimentarius Commission was established in 1961 by the Food and Agricultural Organisation of the United Nations (FAO). A first session was held in Rome in 1963, in conjunction with the World Health Organisation (WHO), the objective being to provide clear guidelines ensuring fair practices in the international food trade and protection of the health of consumers. At the 36th session, in 2013, the commission celebrated its 50th anniversary, marking notable achievements made in promoting food safety. * **At present (2015) the Commission has 185 member countries, comprising 184 member countries and 1 member organisation (EU).** The current Codex guidelines (CAC/GL 66-2008) include revised definitions and terminology on the use of flavourings. The term 'nature identical' (NI) flavouring substance is not retained as such. NI and artificial flavouring substances are now defined as synthetic flavouring substances. Natural flavouring complexes, thermal process flavourings and smoke flavourings have been introduced as new definitions. Accordingly these changes are now reflected in the International Organisation of the Flavour Industry (IOFI) Code of Practice, published in June, 2010. One of the most frequently referred registers of flavouring materials appears in the FEMA GRAS listings. These were compiled by the 'Flavor and Extract Manufacturers Association' of the USA, and comprising those substances 'generally recommended as safe' when used in the minimum quantities required to produce the intended physical (i.e. sensory) effect, and in accordance with the principle of good manufacturing practice, each substance being allocated a FEMA number to enable cross-referencing with other listings, such as the Council of Europe (COE), US Food and Drug Administration (FDA) and Chemical Abstracts Service (CAS). In Europe, flavourings have generally been considered as compound ingredients, and concern has been shown as to the safety of their 'undeclared' components. Following extended interaction with representatives of the European flavour industries, trade associations and so on, a new list was compiled of chemically defined flavouring substances of declared use in the member countries. This list was first published in the Official Journal (OJ) of the European Community on 27th March, 1999. Further work has since been carried out in assessing the level of health risk associated with these ingredients with a view to limitation of use, if and as necessary. In December, 2008, Regulation EC 1334/2008 was published in the OJ, on flavourings and certain food ingredients with flavouring properties. This updates and replaces Council Directive 88/388/EEC of 22nd June 1988. The new regulation entered into force 20th January, 2009, and has been applicable from 20th January, 2011. Again, as with the Codex, a noticeable revision in the terminology applied to flavourings. The definitions of flavourings, given under Article 3 of EC 1334/2008, are broadly in keeping with those of the Codex, but have been condensed into two main categories: * **Flavouring substances:** are defined chemical substances, which include flavouring substances obtained by chemical syntheses or isolated during chemical process, and natural flavouring substances. * **Flavouring preparations:** are flavourings other than defined chemical substances, obtained from materials of vegetable, animal of microbiological origin, by appropriate physical, enzymatic or microbiological processes, either in the raw state of the material, or after processing for human consumption. Definitions are also given for thermal process flavourings and smoke flavourings but, of course, these are not intended for compatibility with soft drink production. Flavouring substances and flavouring preparations may only be labelled as 'natural' if they comply with certain criteria to ensure that consumers are not misled. If the term 'natural' is used to describe a flavour, then the flavouring components used should be entirely of natural origin and, if the source of the flavour is to be labelled, then no less than 95% of the flavouring component should be obtained from the material referred to. ### 5.8 Colours Those of us fortunate enough to possess optical powers capable of distinguishing a variety of colours will appreciate the influence that this particular sensory dimension exercises on our judgement of matters important to our well-being, such as food and drink. The perception of colour gives influence to the taster's reception of the drink and, to this end, there is inevitably some controversy. One point of view states that colours, which possess no measurable nutritional value, can have no place in food or drink, other than that of deceiving the consumer. To a certain extent, this is true but, to appreciate the full value of colour as a food additive (or, more specifically as a soft drink additive), it is necessary to appreciate the synergy between the sensory responses of sight and taste. Colour provides a means of correctly presenting a beverage to the consumer, so that the perceived organoleptic attributes are correctly placed in an ordered sequence of appreciation. Both quality and quantity of colour are of importance, and certain colours will provoke, or perhaps complement, a particular taste. Reds will favour the fruitiness of soft drinks (e.g. blackcurrant, raspberry, strawberry, etc.). Orange and yellow tend towards the citrus flavours. Greens and blues reflect the character of peppermints, spearmint and cool flavours, sometimes herb-like and balsamic, and the browns align with the heavier flavours (e.g. colas, shandies, dandelion and burdock). Therefore, the deceit, if ever intended, is aimed at ensuring that the consumer is able to maximise the enjoyment of the beverage concerned. Where the soft drink is based in part on fruit juices, it may be necessary to restore the appearance of the juice concerned if its natural colours have been destroyed by heat processing, or to intensify such colour when the contribution from the juice is weaker than that normally associated with the effect that the compounded drink is intended to convey. Colour adjustment may also be necessary to ensure uniformity of product, and to offset natural variations in colour tone and intensity associated with the juice type employed in the beverage formulation. Above all, colour is a major parameter in the assessment of quality, serving at the time of production to standardise the product. It can also give useful information as to quality changes during storage, due to colour deterioration caused by temperature fluctuations or microbial spoilage effects, for example. The use of food colours is carefully controlled under various legislations (see **Table 5.5.**). There is, at present, no universal listing of colours for soft drinks, and it is necessary to investigate the permitted list to ensure compliance for goods to be manufactured in, or exported to, a particular country. Both the European Union and the FDA have published lists that are subject to regular review. The greatest concern has been expressed over the use of azo-dye colours, as certain individuals can demonstrate an allergic reaction to some of these. Allergic reactions have been reported most frequently with sunset yellow (E110, FD&C yellow no. 6) and tartrazine (E102, FD&C yellow no. 5). In recent years, new scientific data on health risks to children exposed to azo-dyes has emerged, which has influenced the European Parliament Committee to adopt a more restrictive approach to their use and move towards better labelling of additives containing azo-dyes. From 2011, foods containing some of those colours (colourings E110, E104, E122, E129, E102 and E124) must be labelled, not only with the relevant E-number but also with the words 'may have an adverse on activity and attention in children'. Additionally, in some countries there are commercial constraints imposed, where some institutional bodies and large retailers may refuse, irrespective of legislation, to accept products containing artificial colours. **Table 5.5 Permitted food colourings derived from natural sources (EU Directive 94/36/EC).** | Colour | Sources | Shade| E-no. | Stability | |---|---|---|---|---| | Anthocyanins | Grape skins, elderberry, red cabbage, hibiscus| Red-purple-blue, pH-dependent| E163 | Good | | Beetroot Red | Red beetroots (Beta vulgaris) | Pink to red| E162 | Poor | | Carmine | Cochineal insect (Dachtilopius coccus) | Strawberry red, orange/red hues | E120, E160(a) | Excellent | | Annatto | Seeds of annatto shrub (Bixa orellana) | Orange | E160(b) | Fair | | Beta-carotene | Carrots, algae, palm, synthesised | Yellow to orange | E160(a) | Fair | | Paprika | Red pepper (Capsicum annum)| Orange to red | E160(c) | Fair | | Lutein | Aztec marigold (Tagetes erecta)| Yellow | E161(b) | Good| | Curcumin | Turmeric (rhizomes of Curcuma longa) | Yellow| E100 | Poor | | Chlorophylls | Green-leafed plants | Green| E140, E141| Poor, Good | Although there are a number of food colours suitable for use in soft drinks, it should be appreciated that the contribution of any one of these cannot be entirely predictable. In any soft drink formulation, the colour component, as with all other ingredients, has to be carefully selected for its performance in the presence of certain acids, flavourings, antioxidants and even preservatives. It is essential, therefore, at all stages of development, that meaningful storage trials are completed to ascertain the real contribution from colour in the newly finished beverage. **Table 5.6 Artificial (synthetic) colours permitted in soft drinks to a maximum level of 100 mg/l.** | Colour | E-no. | Colour stability | Colour contribution | |---|---|---|---| | Quinoline yellow | E104 | Good | Greenish yellow | | Tartrazine | E102 | Good | Lemon yellow | | Sunset Yellow | E110 | Good | Orange shade | | Carmoisine (azorubine) | E122 | Good | Bluish red | | Ponceau 4R | E124 | Good | Bright red| | Patent blue FCF | E131 | Good | Bright blue | | Indigotine | E132 | Fair| Dark bluish red | | Brilliant blue FCF | E133 | Good| Greenish blue| | Green S | E142 | Fair | Greenish blue | With the proviso that individual levels of E110, E122 and E124 may not exceed 50 mg/l (EU Colour Directive). Food colours are broadly divided into two classes: natural and artificial. In the USA, these are listed as either 'exempt from certification' or 'certified'. The natural colours are botanical extracts, with the exception of carmine (a red colour), which should perhaps be termed an entomological extract, as it is obtained from the insect Dactilopius coccus, sometimes termed the cochineal beetle, which breeds and feeds on particular cacti indigenous to Central and South America. Table 5.6 lists artificial colours permitted in soft drinks under EU legislation, subject to the controls in use and declaration as mentioned above. ### 5.9 Preservatives A preservative may be defined as any substance that is capable of inhibiting, retarding or arresting the growth of microorganisms, or any deterioration of food due to microorganisms, or masking the evidence of any such deterioration, and so on. In Europe, defined maximum levels of permitted preservatives are given, according to the food substrate concerned. For soft drinks consumable without dilution, the European Directive No. 95/2/EC is as shown in **Table 5.7.** The p-hydroxy benzoates previously cited in the legislation are no longer permitted for use in soft drinks, although they are still included under certain food uses. As mentioned previously, carbon dioxide, while not added specifically as a preservative, contributes towards the inhibition of micro-organic growth and, coupled with other factors (e.g. pH), contributes to the stability of the drink. Carbon dioxide is deemed to be effective at volumes over 2.5 or 3.0 and, for this reason, the incidence of spoilage in carbonated beverages is less than with the non-carbonated versions ('volumes' of CO2 in general terms refers to the number of times the total volume of the gas, adjusted to 760 mm of Hg and 0°C, can be divided by the volume of liquid in which it is dissolved). Although preservatives can be used to good effect in beverage formulations, they should never be considered infallible, and there is no substitute for stringent quality and hygiene controls at every stage of manufacture. Within their own product specification, raw materials should be assigned workable limits for microbial activity, so that there is little chance of excessive contamination in the finished beverage product. Equally, all processing plant, machinery or containers likely to come into contact with the product during manufacture should undergo a thorough cleaning (sanitisation) before use. **Table 5.7 Preservative limits under European Directive 95/2/EC.** | Preservative | Concentration (mg/l) | E-number | |---|---|---| | Sulphur dioxide (carry-over from fruit concentrates only) | 20 | E220| | Benzoic acid |150 | E210 | | Sorbic acid | 20 | E200 | | Benzoic/sorbic acids in combination | 150/250 | E210/E200 | Certain strains of yeast, moulds and bacteria can survive at relatively low pH conditions and some of these can exist and grow in the presence of certain preservatives, so it is important that everything is done to prevent their multiplying. Under favourable conditions, a typical rapidly growing yeast strain can double its numbers every 30 minutes and, at this rate, in 12 hours one yeast could become 16.7 × 10⁹, providing no inhibitory factor is present. ### 5.9.1 Microorganisms and beverages Although there is little evidence of the formation of toxic fermentation products in beverages, the problem of spoilage frequently arises. Because of their utilisation of sugars, yeasts are of most immediate concern. Yeasts are classified with the fungi, and are unicellular for most of their life cycle. Together with moulds and bacteria, they can bring about a deterioration in flavour, producing taints, off-notes and differences in mouthfeel, and so on. Most yeasts can grow with or without oxygen, whereas most bacteria cannot survive in it. The majority of yeasts thrive in temperatures between 25-27°C, some can survive over 70°C and others can exist, apparently quite comfortably, at 0–10°C. Bacteria exhibit some similar diversity in their characteristics, with an optimum growth temperature at around 37°C. Soft drinks provide an ideal growth substrate for many microorganisms, with adequate supplies of the required nutrients. Apart from water, the environmental necessity, typical requirements are sources of carbon (carbohydrates), nitrogen (amino acids), phosphorus (phosphates), potassium, calcium (mineral salts) and traces of other minerals (e.g. sulphur, iron, cobalt and even vitamins). Because of the obvious link with protein formation during cell growth, the presence of combined nitrogen is of particular importance. Also, when it is introduced to beverages via fruit pulp or caramel (colouring), there will be a greater susceptibility to spoilage by certain microorganisms. Perhaps the most difficult aspect of dealing with microbial contamination in soft drinks relates to the delay factor; an apparently good quality product leaves the bottling line for storage and distribution, only to be returned at a later date (perhaps after several weeks), when severe deterioration in performance has taken place. Fortunately, such occurrences are seldom encountered in today's soft drinks industry but, to any manufacturer, it is a nightmare scenario that must be avoided at all costs. A bottled drink constitutes a unique system, which can inhibit or enhance the growth of microorganisms. Micro-flora, if present, will enter a dormant stage, during which their chances of survival are assessed in relation to the immediate surroundings. Following this 'lag' stage, while specific micro-flora may adapt to their new environment and start to grow, there is a burst of species-dependent activity, during which the population doubles repeatedly at a steady rate. Since a bottled drink is a 'closed' system, waste products and diminishing nutrients will serve to slow down the growth and will eventually bring it to a standstill when the death rate increases and all activity stops. The product, however, while perhaps not a health hazard, has been spoiled, and can no longer satisfy its intended function. ### 5.9.2 Sulphur Dioxide Because of the ease with which it can be produced, gaseous SO₂ was one of the first chemical compounds manufactured and used by humans. By Roman times, it was used as a preservative, by burning sulphur before sealing wine into barrels or storage jars. It is one of the most versatile agents used in food preservation, and is well known for its microbiocidal effect on bacteria, moulds and yeasts. Nowadays, it is generally employed in the form of a sulphur dioxide-generating salt. For example, sodium metabisulphite is converted thus in acid medium: S₂O₅ + H₂O → 2NaHSO₃ (MW 880) 2NaHSO₃ + 2Na⁺ + 2H₂O + 2SO₂ (MW 2 x 64) * That is, 190 parts of the metabisulphite produces 128 parts SO₂. **Table 5.8** lists the various salts of the main preservatives. The microbiocidal effect increases as the pH falls below 4.0 and, because of this, SO₂ is ideally suited for most soft drink formulations. However, its preserving action is impaired by a tendency to react with many fruit components of soft drinks, to form organic sulphites, in which state the SO₂ is said to be 'bound'. Although the preservative properties are due mainly to free SO₂, it is necessary to analyse for total SO₂ (i.e. free plus bound), as legislation for safe working requirements refers only to maximum total concentrations. Although SO₂ is used to good effect in the preservation of concentrated citrus juices, with typical concentrations of 1000-2000 ppm m/v, it is now limited under European legislation to no more than 20 ppm in non-alcoholic flavoured drinks containing fruit juice, as carry-over from concentrates only (ref.95/2/EC) (see **Table 5.7.**). There are a number of specific drink products which are permitted to contain higher levels of SO₂ under the same legislation – for example, concentrates/dilutables based on fruit juice and containing not less than 2.5% barley (barley water). However, since this limit has been much reduced from the previous level of 70 ppm, the onus has been squarely placed on manufacturers to attain improved manufacturing practices in terms of plant hygiene. JECFA has recommended an acceptable daily intake (ADI) of not more than 0.7 mg/kg body weight for SO₂. Disadvantages associated with sulphur dioxide are that some tasters can detect it as an unpleasant backnote or taint, and it has a tendency to provoke allergic reactions in some individuals. Asthma sufferers tend to be affected by gaseous sulphur dioxide, small traces of which can promote an asthmatic attack. Foods containing sulphites can, therefore, introduce the risk of gas liberation upon swallowing. **Table 5.8 Preservatives and their salts** || E-no. | Alternative form used at equivalent level | E-no. | |---|---|---|---| | Benzoic acid (m.p. 122°C) CH₅COOH Benzene carboxylic acid | E210 | Sodium benzoate Potassium benzoate Calcium benzoate | E211 E212 E213 | | Sorbic acid (m.p. 133°C) CH₃CH=CH₂-CH₂=CHCOOH 2,4-Hexadienoic acid | E200 | Sodium sorbate Potassium sorbate Calcium sorbate | E201 E202 E203 | | Sulphur dioxide (gas) SO₂ Sulphurous anhydride | E220 | Sodium sulphite Sodium hydrogen sulphite, sodium bisulphite Sodium metabisulphite | E221 E222 E223 | | | | Potassium metabisulphite Calcium sulphite Calcium hydrogen sulphite, calcium bisulphite Potassium bisulphite | E224 E226 E227 E228 | ### 5.9.3 Benzoic Acid and Benzoates Benzoic acid occurs naturally in some fruits and vegetables, notably in cranberries, where it occurs in amounts of the order of 0.08% m