Table of Contents
Introduction to Spoilage of sugar and sugar products
- Sugar is widely used in the food industry both as a food product and as a food preservative.
- Sucrose is the most commonly used sugar and is readily available in nature; however, other sugars such as dextrose, lactose, and fructose are also utilized in the food industry.
- In recent times, polyols like sorbitol, mannitol, xylitol, and maltitol have been introduced as alternatives to sugar in sugar-free products.
- Common sugar-based products used extensively in the food industry include refined sugars, sugar syrups, maple syrup, and honey.
Sucrose
- Sugar (sucrose) is obtained primarily from two major sources: sugar cane (Saccharum officinarum) and sugar beet (Beta vulgaris).
- Smaller quantities of sucrose are also produced from sugar palms (1%), sweet sorghum (0.05%), and maple trees (0.01%).
- Sugarcane and sugar beet undergo multiple processing steps to produce 99.9% pure sucrose.
- These processes include crushing and extraction, clarification, evaporation/crystallization, centrifugation, and filtration.
Contamination source of sucrose
- Soil
- Raw materials, including sugarcane and sugar beet
- Handlers involved in processing
- Equipment and machinery used in production
- Poor hygienic handling practices
- Inadequate cleaning of sugarcane press knives and contact surfaces
- Airborne contamination
Spoilage of sucrose
- The microbial population undergoes changes during the processing of sugarcane and sugar beet into sucrose.
- Spoilage-causing microorganisms that contaminate raw juice depend on the specific microorganisms present during sugarcane and sugar beet processing.
- Common microorganisms found in sugarcane include Pseudomonas, Bacillus, Enterobacteriaceae, Lactobacillus, Erwinia, Leuconostoc, Flavobacterium, Xanthomonas, Corynebacterium, yeasts, and molds.
- Common microorganisms found in sugar beets include Pseudomonas, Arthrobacter, Erwinia, Streptomyces, Bacillus, Clostridium, Flavobacterium, and yeasts.
- Yeasts linked to raw juice spoilage include Saccharomyces, Candida, and Pichia.
- Various microorganisms are associated with different major steps in sugarcane and sugar beet processing.
| Product | Process Step | Microorganisms | Defects |
|---|---|---|---|
| Sugarcane | Pre-harvest | Flavobacterium, Lactobacillus, Xanthomonas, Enterobacter (Klebsiella pneumoniae), Pseudomonas, Erwinia, Leuconostoc, Bacillus, Corynebacterium, yeasts, molds | Souring |
| Post-harvest | Leuconostoc | Souring, sugar loss, dextran formation | |
| Crushing and extraction | Leuconostoc, Enterobacter, yeasts | Souring, sugar loss, alcohol production | |
| Clarification | None | — | |
| Evaporation / Crystallization / Centrifugation | Thermophilic spore formers | — | |
| Refining | Thermophilic spore formers | — | |
| Sugar beet | Pre-harvest | Pseudomonas, Bacillus, Arthrobacter, Erwinia, Flavobacterium, Streptomyces, yeasts, Clostridium | Acid production |
| Post-harvest storage | Bacillus, Leuconostoc | Slime formation, dextran and levan production | |
| Fluming and washing | Pseudomonas, Flavobacterium | Acid production, corrosion | |
| Extraction | Bacillus stearothermophilus, Clostridium, thermophilic cocci | Acid production, sugar loss, hydrogen sulfide production | |
| Crystallization | Thermophilic spore formers | Introduction of spores into final products |
- Bacteria linked to raw sugar spoilage include Bacillus stearothermophilus, Bacillus coagulans, Clostridium thermosaccharolyticum, Desulfotomaculum nigrificans, and various mesophilic bacteria.
- Yeasts present in raw sugar are predominantly osmophilic, with common genera including Zyrosaccharomyces, Hansenula, Pichia, Torulopsis, Candida, Dekkeromyces, and Endomycopsis.
- Molds in raw sugar are typically xerophilic molds.
- Sugar refining processes destroy microorganisms when present; however, recontamination can occur from surviving thermophilic spores.
- Microorganisms associated with raw and refined sugar can cause various defects in the final product.
| Product | Microorganisms | Defects |
|---|---|---|
| Raw sugar | Zygosaccharomyces rouxii, xerophilic molds | Sugar loss; production of invert sugars; acid formation; increase in water activity |
| Refined sugars | Surviving thermophilic spores | Introduction of spores into final products |
Preservation of sucrose
- Sugar has a naturally low water activity, making it microbiologically stable and suitable for storage at room temperature for several months.
- Spoilage occurs when sugar absorbs moisture; therefore, during storage, vermin should be excluded to keep the sugar dry.
- Sugarcane and sugar beet should be thoroughly cleaned and stored in a controlled atmosphere.
- Fungal growth can be inhibited by using gases such as 6% carbon dioxide and 5% oxygen.
- Chemical preservatives are applied during the sugar refining process.
- Hygienic conditions must be maintained throughout the entire sugar refining process.
- Pasteurization is employed to remove microorganisms from sugarcane or sugar beet juices.
- Additional preservation methods for sugarcane or sugar beet juices include Ultrasound, Irradiation, High-Pressure Processing (HPP), and Pulsed Electric Field (PEF) treatment.
Sugar syrup
- Liquid sugar made from cane or beet sugar is produced by dissolving crystalline refined sugar in water.
- It typically contains a sugar concentration ranging from 66 to 76° Brix.
- Sugar syrups are widely used in products including confectionery, beverages, bakery goods, ice cream, jams, jellies, and meat products.
Contamination source of sugar syrup
- Water and sugar used in production
- Equipment and machinery involved in processing
- Poor hygienic handling practices
- Contaminated raw materials
- Airborne contamination
- Improper storage conditions
Spoilage of sugar syrup
- Adding water to refined sugar to produce liquid sugar increases its susceptibility to microbial growth.
- Sugar syrups can be contaminated by various microorganisms, particularly spore-forming bacteria, yeasts, and molds.
- Osmophilic yeasts and xerophilic molds are the primary spoilage organisms in sugar syrup.
- Common spoilage yeasts include Zygosaccharomyces rouxii, Saccharomyces cerevisiae, and Saccharomyces mellis.
- Common spoilage molds include Aspergillus glaucus and Penicillium expansum.
- These microorganisms can produce foul flavors through the formation of alcohol, lactic acid, and other organic acids.
Preservation of sugar syrup
- Sugar syrup can be preserved by filtration, heating, or ultraviolet light treatment to remove or inactivate microbial contaminants.
- Pasteurization can be applied at 65°C for 30 minutes, 75°C for 25 seconds, or 85°C for 15 seconds to eliminate microorganisms.
- Pasteurized sugar syrup can be stored under refrigerated conditions to extend shelf life and prevent microbial contamination.
- Additional preservation techniques include Ultrasound, Irradiation, Pulsed Light (PL), High-Pressure Processing (HPP), and Pulsed Electric Field (PEF) treatment.
Maple syrup
- Maple syrup is derived from the sugar maple tree (Acer saccharum).
- Maple sap consists of 95–99% water, along with minerals such as calcium and potassium, 2–5% sucrose, various organic acids, and vitamins.
- The sap is collected by drilling and tapping the trees.
Contamination source of maple syrup
- Uncharacteristic environmental changes
- Improper sap storage conditions
- Unsanitary processing practices
- Equipment used for sap collection
Spoilage of maple syrup
- Sap is sterile while inside the tree’s xylem, but once exposed to the environment, it becomes highly susceptible to microbial growth.
- Maple syrup’s water activity, ranging from 0.83 to 0.86, prevents the growth of bacterial pathogens.
- The most common bacterium found in sap is Pseudomonas fluorescens, along with certain yeast species.
- Spoilage-causing bacteria include Pseudomonas, Aerobacter, Leuconostoc, Enterobacteriaceae, and Bacillus species.
- Spoilage-causing fungi include Phialophora, Ascocoryne, Phoma, Alternaria, Penicillium, Fusarium, Gliocladium, Cephalosporium, Cladosporium, Candida, Trichoderma, and Actinomycetes.
- Different microorganisms are associated with maple syrup at various stages of processing, leading to specific defects.
| Processing Stage | Bacteria | Bacterial Defects | Fungi | Fungal Defects |
|---|---|---|---|---|
| Collection and Tapping | Achromobacter spp., Leuconostoc spp. | Reduced sap yield, ropy sap | Molds: 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 | |
| Chryseobacterium spp. (including Epilithonimonas spp.), Enterobacteriaceae spp. | Reduced sap yield | Yeasts: 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 in sap include:
- Green sap – caused by fluorescent pseudomonads
- Red sap – caused by red-pigmented yeasts and certain bacteria
- Milky sap – caused by Bacillus species
Preservation of maple syrup
- Store collected sap at 40°C until further use to control microbial growth during processing.
- Clean all equipment regularly to prevent contamination.
- Use filtration, evaporation, or ultraviolet (UV) treatment to remove or inactivate microbial contaminants in syrup.
- Apply pasteurization to sugar syrup:
- 65°C for 30 minutes
- 75°C for 25 seconds
- 85°C for 15 seconds
- Store pasteurized sugar syrup under refrigerated conditions or can it to extend shelf life and prevent microbial contamination.
- Consider advanced preservation techniques such as:
- Ultrasound
- Irradiation
- Pulsed Light (PL)
- High-Pressure Processing (HPP)
- Pulsed Electric Field (PEF)
Honey
- Honey is a natural sweet substance produced by honey bees, defined as the nectar and saccharine exudates of plants, gathered, modified, and stored in the honeycomb by Apis mellifera.
- It 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.
- Composition typically includes 15–21% water, 30–35% glucose, 35–45% fructose, 1–3% sucrose, 10–12% maltose, along with organic acids, minerals, proteins, amino acids, and enzymes.
- Water activity ranges between 0.54 and 0.75, with an acidic pH between 3.2 and 4.5.
Contamination source of honey
- Flowers and pollen
- Digestive tracts of honeybees
- Dirt, dust, and air
- Food handlers
- Equipment used
Spoilage of honey
- Microorganisms capable of surviving in honey are those that can tolerate its high sugar concentration, acidity, and other antimicrobial properties.
- Honey can be contaminated by a variety of bacteria, yeasts, and molds.
- Most bacteria and microbes remain dormant in honey because of its antibacterial nature, which prevents their growth and reproduction.
- Yeasts and molds can survive in honey, and certain vegetative and spore-forming bacteria can also persist.
- Osmophilic yeasts are the primary cause of honey spoilage, as they are more capable of growing in honey compared to bacteria and molds.
- Bacterial species detected in honey include Bacteridium, Bacterium, Bacillus (B. cereus and B. pumilus), Brevibacterium, Enterobacter, Flavobacterium, Micrococcus, Neisseria, Pseudomonas, and Xanthomonas.
- Yeast species found in honey include Rhodotorula, Debaryomyces, Hansenula, Lipomyces, Oosporidium, Pichia, Torulopsis, Trichospora, Nematospora, Schizosaccharomyces, Schwanniomyces, Torula, and Zygosaccharomyces.
- Mold species associated with honey include Ascosphaera, Aspergillus, Cephalosporium, and Penicillium.
- These microorganisms can produce alcohol, carbon dioxide, lactic acid, and other organic acids, leading to undesirable flavors in honey.
Preservation of honey
- Honey naturally acts as a preservative due to its strong antimicrobial activity, which is attributed to its osmotic effect, acidity, hydrogen peroxide content, and phytochemical components.
- It exhibits bactericidal effects against many pathogenic microorganisms, including Salmonella spp., Shigella spp., Escherichia coli, Vibrio cholerae, and various Gram-negative and Gram-positive bacteria.
- Pasteurization is carried out at 71°C for 5 minutes, followed by rapid cooling to 38°C.
- After pasteurization, honey can be stored under refrigeration or canned to extend its shelf life and prevent microbial contamination.
References
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