CONTAMINATION, PRESERVATION AND SPOILAGE OF SUGAR AND SUGAR PRODUCTS

CONTAMINATION * The raw juice expressed from sugarcane may become high in microbial content unless processing is prompt. * The relevant microorganisms are those from the sugarcane and the soil contamination it and therefore comprise slime producers such as species of Leuconostoc and Bacillus representatives of the genera Micrococcus, Flavobacterium, Pseudomonas; a variety of yeast, chiefly in genera Saccharomyces, Candida, and Pichia and a few molds. * Much contamination may come from debris or fine particles on the sides or joints of troughs at the plant. * If organisms grow to an extent then inversion of sucrose or even destruction of sugar may take place. * Activities of the organisms take place from cutting of the cane through extraction to clarification of the juice, a process which kills yeasts and vegetative cells of bacteria. * Bacterial spores are present from then on, through sedimentation, filtration, evaporation, crystallization, and centrifugation, but may be reduced in number by these processes, although spores of thermophiles may be added from equipment. * Bagging of raw sugar may also add some micro organisms. * During the refining of raw sugar contamination may come from equipment, and organisms are added during bagging. * In manufacture of beet sugar, clean beets are sliced into thin slices and the sugar is removed by diffusion process at 60 to 85 C. sources of contamination are flume water and diffusion- battery waters. * Thermophiles may grow into the latter at 70 c. * Contamination may also take place during refining and bagging of the sugar. * Granulated sugar are now very low in microbial content for the most part, containing from a few to a several hundred organisms per gram, mostly bacterial spores.

MAPLE SIRUP * Sap of the sugar maple in vascular bundles is sterile. It becomes contaminated from the outside sources in the tapholes and by the spout, plastic tubing, buckets and other collecting vessels. * If a period of unusual warmth occurs before the sap is collected, considerable growth of yeast and bacteria may take place in the sap. * Microorganisms entering sap between the flow from the tree and being boiled and concentrated are mostly psychrotrophic, gram negative rods of Pseudomonas, Flavobacterium, plus yeasts and molds. * Paraformaldehyde taphole pellets are inserted into the drilled holes to prevent microbial growth from blocking the flow. * In sugar-bush locations that are exposed to unusual dust and air contamination, collection of sap by a series of plastic tubes results in lower bacterial contamination. * However in a well controlled sugar bush the microbial content of sap tubing is not significantly different from that obtained by using individual pails. * Sap- gathering tanks, usually mobile, must be sanitized regularly to prevent development of high numbers of bacteria in the sap when it reaches the evaporator. * Bacterial counts in sap are usually less than 10,000 per millimeter, but higher number can develop as a result of warmer temperatures near the end of the season and poor sanitation.

HONEY * The chief sources of microorganisms in honey are the nectar of flowers and the honeybee. * Yeasts have been shown to come from the nectar and the intestinal content of the bee; bacteria also comes from the latter source. * Honey rarely contains staphylococci or enteric bacteria. Common isolates are usually acidophilic and glycolytic yeasts, which can damage the product. * Honey has been found to contain lysozyme, an enzyme with a bacteriostatic as well as lytic effect on most gram positive bacteria. * The use of antibiotics such as neomycin and streptomycin is widespread in beekeeping, and these antibiotics have been found in honey would, of course, have an effect on its microbial flora. * Honey is one of the suspected food vehicles for the source of C.botulinum spores in cases of infant botulism. * About 10% of the suspected honey samples contained viable spores. * A study by Ruiz- Argueso and Rodriguez-Navarro (1975) suggested that Gluconobacter and Lactobacillus are the two main groups of bacteria present during maturation of nectar to honey.

CANDY * Candies from retail market contain 0 to 2 million bacteria per piece, but most pieces harbor no more than a few hundred. Few coliform bacteria are found. * The candies receive most of their contamination from their ingredients, although some contamination may be added to unwrapped pieces by air, dust, and handling. * The several thousand types of candies and confections can be divided into two categories for microbial consideration: (1) Cold processed and (2) hot processed confections. * Molded chocolates and chocolate coatings for creamed centers fall into the first category. * Temperature during processing may only approach pasteurization temperature. * Examples of the second categories include hard candies, jellies, caramels and fudges. * Processing temperature for these items vary, but they all are exposed to a more severe heat treatment than are items in the first category. * Candies are infrequently associated with food-poisoning outbreaks, but chocolate candies have been incriminated in cases of salmonellosis. The problem appears to be one of cross contamination in the plant between raw and roasted cocoa beans, with the raw beans or environmental isolates serving as the source of contamination. * Although temperature of 60 C for 10 hr are not common during processing and blending of milk chocolate, the low moisture content or the dryness of the chocolate apparently protects the salmonellae from heat.

PRESERVATION * Like cereals sugars normally have aw’s so low that microorganisms cannot grow. Only when moisture has been absorbed is there any chance for microbial spoilage. * Storage conditions should be such that vermin are kept out and the sugar is kept dry. * Cane or sugar beets may be kept in controlled atmosphere. Fungal growth is inhibited by 6% CO2 and 5% O2. * During the manufacture of raw sugar and subsequent refining process the number of micro organisms present, which may be larger during extraction from cane or sugar beet, are reduced by most subsequent processes, e.g. clarification, evaporation, crystallization, centrifugation and filtration. * Chemical preservatives are effective in reducing microbial numbers during sugar refining. * Special treatment to reduce numbers and kinds of organisms may be given during refining when the sugar is to be used for a special purpose, e.g. for soft drinks or canning. * Care is taken to avoid buildup of organisms and their spores during processing, and numbers may be reduced by irradiation with ultraviolet rays or combined action of heat and hydrogen peroxide. * Because of their high sugar concentration and low aw, most candies are not subject to microbial spoilage, although soft filling of chocolate covered candies may support the growth of microorganisms. * The bursting of chocolates is prevented by a uniform and fairly heavy chocolate coating and use of fondant and other filling that will not permit the growth of gas formers. * Syrups and molasses usually have undergone enough heating to destroy most microorganisms but should be stored at cool temperatures to prevent or slow chemical changes and microbial growth. Some molasses may contain enough sulfur dioxide to inhibit microorganisms, but most syrups and molasses contain no added preservatives and prevent microbial growth because of high osmotic pressure of the sugar solution. The osmotic pressure increases with the extent of inversion of the sucrose. * Mold growth on the surface is reduced by periodic mixing of the syrup or molasses. * The boiling process during the evaporation of maple sap to maple syrup kills the important spoilage organisms. Such syrup, boiled hot and in completely filled containers, usually keeps well. * Honey distributed locally on a small scale usually is not pasteurized and therefore may be subject to crystallization and to possible spoilage in time by osmophilic yeast. Commercially distributed honey is pasteurized at 71 C to 77 C for a few minutes. A recommended treatment is to heat fairly rapidly to at least 71 C, hold there for 5 min, and cool promptly to 2.2 to 8 C.

SPOILAGE * The spoilage of sugars or concentrated solutions of sugar if limited to that caused by osmophilic or xerotolerant microorganisms. Certain yeasts, especially those of the genus Saccharomyces, and certain molds would be the principal spoilage flora. * Some species of bacteria have also been suggested as possible spoilage problems, including species of Bacillus and Leuconostoc. As the sugar concentration decreases, increasing numbers of kinds of organisms can grow, so that sap from maple tree would show types of spoilage that maple syrup could not.

SUCROSE
During the manufacture of sugar, the original cane or beet juice becomes more and more purified towards sucrose and the concentration of sugar in solution becomes greater and greater until finally crystalline sugar is attained plus molasses that is high in sugar. The purer the product, the poorer it becomes as a culture medium for microorganisms; the more concentrated it gets, the fewer kinds of organisms can grow in it.
Raw Juice
The raw cane or beet juice is not high in sugar and contains a good supply of accessory foods for microorganisms; it therefore is readily deteriorated by the numerous organisms present if sufficient time is allowed. Until clarification, gum and slime may be formed, e.g. dextran by Leuconostoc mesenteroides or L. dextranicum and levan by Bacillus spp. or, less commonly, by yeasts or molds.
Sugar in Store
Liquid sugar with liquid content as high as 67 to 72 brix will support the growth of yeasts (Saccharomyces, Candida, Rhodotorula) and molds which may enter from the air. Dilution by absorption of moisture at the surface may result in growth of microorganisms and hence deterioration of the product. This can be prevented by circulation of the filtered sterile air across the top of the storage tank or exposure to ultraviolet lamps.
Molasses and syrups
Microbial spoilage of molasses is not common, although it is difficult to sterilize by heat because of the protective effect of the sugar. Canned molasses or syrup may be subjected to spoilage by osmophilic yeasts that survive the heat process. Molasses or syrups exposed to air will mold, in time, on the surface, and this may also occur at the surface of a bottled or canned syrup if air is left there and contamination has taken place prior to sealing. Some molasses are acidic enough to cause hydrogen swells upon long storage.
MAPLE SAP AND SIRUP
As previously stated, sap from the sugar maple becomes contaminated when drawn. Although a moderate amount of growth may improve flavor and color, the sap often stands under conditions that favor excessive growth of microorganisms and hence spoilage. Five chief type of spoilage are recognized: (1) ropy or stringy sap, usually caused by Enterobacter aerogenes , although Leuconostoc spp. Maybe responsible, (2) cloudy, sometime greenish sap resulting from the growth of Pseudomonas fluorescens with species of Alkaligens and Flavorbacterium sometimes contributing to cloudiness (3) red sap, colored pigment of red bacteria , example Micrococcus roseus, or of east or east like fungi (4) sour sap , catch all grouping for types of spoilage not showing a marked change in color but having a sour odor and caused by any of a variety of kinds of bacteria or yeast and (5) moldy sap, spoiled by molds.

Maple syrup can be ropy because of Enterobacter aerogenes , yeasty as the results of growth of species of Saccharomyces yeast, pink from the pigment of Micrococcus roseus, or moldy at the surface, where species of Aspergillus, Penicillium or other genera may grow. The syrup may become dark because of alkalinity produced by bacteria growing in the sap an inversion of sucrose. Maple syrup keeps well unless moisture, at which time moulds may grow.
HONEY
Honey is variably in composition but must contain no more than 25 percent moisture. Because of its high sugar content, 70 to 80 %, mostly glucose and levulose, and its acidity, pH .2 to 4.2, the chief cause of its spoilage is osmophilic yeasts; species of Zygosaccharomyces, such as Z. mellis, richteri, or nussbaumeri, or Torula (Cryptococcus) mellis. Most molds do not grow well on honey, although species of Penicillium and Mucor have developed slowly.
Most honey yeasts do not grow in the laboratory in sugar concentration as high as those in usually found in honey. Therefore, special theories for the initiation of growth of yeasts in honey have been advanced: (1) Honey, being hygroscopic, becomes diluted at the surface, where yeasts begin to multiply and soon become adapted to the high sugar concentration, (2) crystallization of glucose hydrate from honey leaves a lowered concentration of sugars in solution, or (3) on long standing, yeasts gradually become adapted to the high sugar concentrations. The critical moisture content for the initiation of yeast growth has been placed at 21%. The degree of inversion of sucrose to glucose and levulose by the bees and the content of available nitrogen also are listed as factors determining the likelihood of growth. The fermentation process usually is low, lasting for months, and the chief products are carbon dioxide, alcohol, and nonvolatile acids which gave an off-flavor to the honey. Darkening and crystallization usually accompany the fermentation.
CANDY
Most candies do not subject to microbial spoilage because of their comparatively high sugar and low moisture content. Exceptions are chocolates with soft centers of fondant or of inverted sugar, which, under certain conditions, burst or explode. Yeasts growing in these candies develop a gas pressure which may disrupt the entire candy or more often will push out some of the syrup or fondant through a weak spot in the chocolate coating. Often this weak spot is on the poorly covered bottom of the chocolate, where a cylinder of fondant squeezes out. The defect is prevented by using a filling that will not support the growth of the gas formers and by coating the candy with a uniformly thick and strong layer of chocolate. The microbial spoilage flora of many confectionery products is summarized in fig….