Spoilage of sugar and sugar products and their preservations

  • Sugar is the widely used sugar in the food industry as a food product as well as a food preservative. 
  • Sucrose is the widely used sugar and is easily available in nature however, dextrose, lactose, and fructose are also used in the food industry.
  • Recently, polyols such as sorbitol, mannitol, xylitol, and maltitol have been used as replacements for sugar in sugar-free products.
  • Some of the sugar products widely used in the food industry are refined sugars, sugar syrups, maple syrup, and honey.
Spoilage of sugar and sugar products and their preservations

Sucrose

  • Sugar (sucrose) is derived from two main sources, sugar cane (Saccharum officinarum) and sugar beet (Beta vulgaris).
  • Sucrose is also produced from sugar palms (1%), sweet sorghum (0.05%), and maple trees (0.01%) but in a small amount.
  • The sugarcane and sugar beet go through various processes to form 99.9 % pure sucrose. 
  • Such process includes crushing and extraction, clarification, evaporation/crystallization, centrifuge, filtration.

Contamination source of sucrose

  • Soil
  • Raw materials (Sugarcane, sugar beet)
  • Handers
  • Equipment and machine used 
  • poor hygienic handling, 
  •  inappropriate cleaning of the sugar cane press knives, interaction surfaces, 
  • airborne contamination

Spoilage of sucrose

  • The microorganism population changes during the processing of sugarcane and sugar beet to sucrose.
  • The spoilage-causing microorganism which contaminated raw juice depends upon the microorganisms during the processing of sugarcane and sugar beets.
  • Microorganisms species found in sugarcane include Pseudomonas, Bacillus, Enterobacteriaceae, Lactobacillus, Erwinia, Leuconostoc, Flavobacterium, Xanthomonas, Corynebacterium, yeasts, and molds.
  • Microorganisms species found in sugar beets include Pseudomonas, Arthrobacter, Erwinia, Streptomyces, Bacillus, Clostridium, Flavobacterium, and yeasts.
  • The yeasts associated with raw juice spoilage are Saccharomyces, Candida, and Pichia.

Microorganisms associated with the major steps in sugarcane and sugar beet processing are:

Product

Process step

Microorganisms 

Defects

Sugarcane

Pre-harvest

Flavobacterium, Lactobacillus, Xanthomonas, Enterobacter (Klebsiella pneumonia), Pseudomonas, Erwinia, Leuconostoc, Bacillus, Corynebacterium; yeasts, molds

Souring

Post-harvest

Leuconostoc

Souring, sugar loss/ dextran formation

Crushing and extraction

Leuconostoc, 

Souring

Enterobacter

Sugar loss

yeasts

Alcohol production

Clarification

None

 

Evaporation/

crystallization/

centrifugation

Thermophilic spore formers

 

Refining

Thermophilic spore formers

 

 

Sugar beet

Pre-harvest

Pseudomonas, Bacillus, Arthrobacter, Erwinia, Flavobacterium, Streptomyces, yeast, Clostridium

Acid production, 

Post-harvest storage

Bacillus, 

Slime formation

Leuconostoc

Dextrans, levans

Fluming and washing

Pseudomonas, 

Acid production

Flavobacterium 

corrosion

Extraction

B. stearothermophilus,

Acid production

Clostridium

Sugar loss

thermophilic cocci

Hydrogen sulfide production

Crystallization

Thermophilic spore formers

Introduction of spores into final products

  • The bacteria associated with raw sugar spoilage include B. stearothermophilus, B. coagulans, C. thermosaccharolyticum, Desulfotomaculum nigrificans, and mesophilic bacteria.
  • Yeast species found in raw sugar are mainly osmophilic. Zyrosaccharomyces and species of Hansenula, Pichia, Torulopsis, Candida, Dekkeromyces, and Endomycopsis have been found in raw sugar.
  • Molds found in raw sugar are Xerophilic molds.
  • The refining of sugar destroys microorganisms if they are present. However, recontamination may occur by surviving thermophilic spores.

Microorganisms associated with raw sugar and refined sugar and the defects caused by it are:

Product

Microorganisms

Defects

Raw sugar

Z.rouxii

Sugar loss

Xerophilic molds

Invert sugars are produced, Acid production, increase in water activity

Refined sugars

Surviving thermophilic spores

Introduction of spores into final products

Preservation of sucrose

  • Sugars’ water activity is so low that sugar is microbiologically stable and can be stored at room temperature for several months. 
  • Sugar only gets spoiled when it absorbs the moisture so during storage the vermin should be kept out so that the sugar remains dry.
  • The sugarcane and sugar beet should be cleaned and stored in a controlled atmosphere.
  • Fungal growth is inhibited by using gases like 6 % carbon dioxide and 5% oxygen.
  • Chemical preservatives are used during a sugar refining process.
  • The hygienic condition should be maintained throughout the whole sugar refining process.
  • Pasteurization is used as a preservation method for the removal of microorganisms present in sugarcane or sugar beet juices.
  • Other various methods such as Ultrasound, Irradiation, High-pressure Processing (HPP) and pulse electric field (PEF) can be applied in sugarcane or sugar beet juices for the removal of microorganisms present in them.

Sugar syrup

  • Liquid sugar manufactured from cane or beet sugar is produced by mixing crystalline refined sugar with water.
  • It has a sugar content of 66 to 76° Brix.
  • Sugar syrups are used in a variety of products such as confectionery, beverages, bakery, ice cream, jams, jellies, and meat products.

Contamination source of sugar syrup

  • Water, sugar 
  • Equipment and machine used 
  • poor hygienic handling, raw material
  • air-borne contamination
  • improper storage condition

Spoilage of sugar syrup

  • The addition of water to refined sugar to produce liquid will make it more susceptible to microbial growth.
  • Many microorganisms, mainly spore-forming bacteria, yeasts, and molds, contaminate sugar syrups. 
  • The osmophilic yeasts and xerophilic molds are the main microorganisms to cause spoilage of sugar syrup.
  • Yeasts such as Zygosaccharomyces rouxii, Saccharomyces cerevisiae, Saccharomyces Mellis, and molds such as Aspergillus glaucus, Penicillium expansum may grow in sugar syrup.
  • The microorganisms cause foul flavors due to the production of alcohol, lactic acid, and other organic acids.

Preservation of sugar syrup

  • Sugar syrup can be filtered, heated, or passed over ultraviolet lamps to remove or inactivate microbial contaminants.
  • Pasteurization is applied to sugar syrup for 65° C for 30 minutes or 75°C for 25 secs or 85°C for 15 secs to remove the microorganisms present in them.
  • Further, the pasteurized sugar syrup can be stored at refrigerated temperature to prolong its shelf-life and to avoid microbial contamination.
  • Other various methods such as Ultrasound, Irradiation, and Pulsed light (PL), High-pressure processing (HPP) and pulse electric field (PEF) can be applied in sugar syrup to remove the microorganisms present.

Maple syrup

  • Maple syrup is obtained from the sugar maple tree Acer Saccharum.
  • Maple sap is made up of 95–99% water and contains minerals ( calcium and potassium), 2–5% sucrose, and several organic acids, and vitamins.
  • Trees are drilled and tapped to collect sap.

Contamination source of maple syrup

  • uncharacteristic environmental changes
  • improper sap storage conditions 
  • unsanitary processing practices
  • equipment used to collect sap

Spoilage of maple syrup

  • The sap is considered a sterile liquid when in the tree xylem, however, upon environmental exposure, it becomes highly susceptible to microbial growth.
  • The water activity of range between 0.83 and 0.86 in maple syrup eliminates the growth of bacterial pathogens.
  • The most prevalent bacterium in the sap is Pseudomonas fluorescens, with some yeasts.
  • The bacteria that cause spoilage include Pseudomonas, Aerobacter, Leuconostoc, Enterobacteriaceae, and Bacillus spp.
  • The fungi that cause spoilage include Phialdophora, Ascocoryne, Phoma, Alternaria, Penicillium, Fusarium, Gliocladium, Cephalosporium, Cladosporium, Candida, Trichoderma, and Actinomycetes.

Microorganisms associated with maple syrup during processing and the defects caused by it are:

Processing

Bacteria

Defects

Fungi

Defects

Collection and tapping

Achromobacter spp, Leuconostoc spp, 

Reduced sap yield, Ropy sap

Mold

Acremonium spp. (including Cephalosporium spp., Alternaria spp, Ascocoryne spp.

Reduced sap yield/

quality

Bacillus spp., Flavobacterium spp.

Reduced sap yield, Ropy sap, Buddy sap

Aspergillus spp. (including Eurotium spp.) Cladosporium spp, Fusarium spp, Penicillium spp

Reduced sap yield/

quality, surface mold

Chyrseobacterium spp. (including Epilithonimonas spp.), Enterobacteriaceae spp, 

Reduced sap yield

Yeast

Candida spp.

Cryptococcus spp., 

Rhodotorula spp.

Saccharomyces spp.

Reduced sap yield/

quality, 

Reduced syrup grade

Klebsiella spp

Ropy sap

Micrococcus spp, Pseudomonas spp

Reduced sap yield, buddy sap

Plantibacter spp, Staphylococcus spp

Buddy sap

Storage

Aeromonas spp., 

Brevibacillus spp., Brevundimonas spp., Kluyvera spp. 

 

Cytospora spp.

Mucor spp.

Rhizopus spp.

Surface mold

Packaging

Agrobacterium spp. Bacteroides spp.

 

 

Some spoilage defects associated with sap include:

  • green sap caused by fluorescent pseudomonads, 
  • red sap caused by red yeasts and some bacteria, 
  • milk sap caused by Bacilli.

Preservation of maple syrup

  • Microbial growth during processing can be controlled by storing the collected sap at 40°C until further use.
  •  All equipment should be cleaned on a regular frequency.
  • The syrup can be filtered, evaporated, or passed over ultraviolet lamps to remove or inactivate microbial contaminants.
  • Pasteurization is applied to sugar syrup for 65° C for 30 minutes or 75°C for 25 secs or 85°C for 15 secs to remove the microorganisms present in them.
  • Further, the pasteurized sugar syrup can be stored at refrigerated temperature or canned to prolong its shelf-life and to avoid microbial contamination.
  • Other various methods such as Ultrasound, Irradiation, and Pulsed light (PL), High-pressure processing (HPP) and pulse electric field (PEF) can be applied in sugar syrup to remove the microorganisms present.

Honey

  • Honey is the natural sweet substance produced by honey bees which also is defined as the nectar and saccharine exudation of plants, gathered, modified, and stored as honey in the honeycomb by honeybees, Apis melifera.
  • Honey is widely used in the food industry in products such as condiments, salad dressings, barbecue sauce, peanut butter, dairy products, meats, beverages, snacks, bread, cereal products, and candy.
  • It generally contains 15 –21% water, 30 –35% glucose, 35 –45% fructose, 1 – 3% sucrose, 10 –12% maltose, organic acids, minerals, proteins, amino acids, and enzymes.
  • The water  activity of honey ranges between 0.54 and 0.75 with an acidic pH range  of between 3.2 and 4.5

Contamination source of honey

  • Flowers, pollen, 
  • the digestive tracts of honeybees, 
  • dirt, dust, and air
  • food handlers
  • equipment used

Spoilage of honey

  • Microorganisms that survive in honey are those that withstand the concentrated sugar, acidity, and other antimicrobial characters of honey.
  • A wide range of bacteria, yeasts, and molds are found contaminating the honey.
  • Most bacteria and other microbes cannot grow or reproduce in honey i.e. they are dormant and this is due to the antibacterial activity of honey.
  • Yeasts and molds can survive in honey. Some vegetative and spore-forming bacteria can survive in honey.
  • The microorganisms found in honey are osmophilic yeasts, which can grow and cause spoilage as compared to bacteria and mold.
  • Bacteria species found in honey are Bacteridium, Bacterium, Bacillus (B. cereus and B. pumilus), Brevibacterium, Enterobacter, Flavobacterium, Micrococcus, Neisseria, Pseudomonas, and Xanthomonas.
  • The yeast species found in honey are Rhodotorula, Debaryomyces, Hansenula, Lipomyces, Oosporidium, Pichia, Torulopsis, Trichospora, Nematospora, Schizosaccharomyces, Schwanniomyces, Torula, and Zygosaccharomyces.
  • The mold species found in honey are Ascosphaera, Aspergillus, Cephalosporium, and Penicillium.
  • The microorganisms cause foul flavors due to the production of alcohol, CO2, lactic acid, and other organic acids.

Preservation of honey

  • Honey itself is a preservative agent. Its high antimicrobial activity is a result of an osmotic effect, acidity, hydrogen peroxide, and phytochemical factors.
  • Honey shows a bactericidal to many pathogenic microorganisms such as Salmonella spp, Shigella spp, Escherichia coli, Vibrio cholerae, and other Gram-negative and Gram-positive organisms.
  • Honey is pasteurized at 71°C for 5 minutes and cool promptly to 38°C.
  • Further, the pasteurized honey can be stored at refrigerated temperature or canned to prolong its shelf-life and to avoid microbial contamination.

References

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