Orange Serum Agar

Orange Serum Agar

Reference Medium for Enumeration of Aciduric Spoilage Microorganisms

Product Identification

Chemical & Physical Information

Product Name: Orange Serum Agar
Medium Type: Selective solid culture medium
Form: Dehydrated powder

Product Description

Orange Serum Agar is the official reference solid culture medium for the enumeration and isolation of aciduric spoilage bacteria, yeasts, and moulds from citrus juices, fruit-based beverages, concentrates, syrups, and soft drinks. The formulation closely mimics the natural low-pH citrus environment, enabling reliable recovery of organisms that survive and proliferate in acidic products.

This medium is specified as the mandatory reference medium in ISO 13681, IFU Method No. 3, and international fruit-juice and beverage microbiology standards. It is routinely used for quality control testing in juice processing plants, beverage manufacturers, and contract microbiology laboratories.

Ausamics Orange Serum Agar is supplied as a high-quality dehydrated powder to ensure consistent selectivity, reproducible recovery, and reliable colony development.

Principle of the Medium

Functional Components

Orange Serum: Provides natural organic acids, sugars, and growth factors characteristic of citrus products
Yeast Extract: Supplies vitamins and growth factors
Tryptone / Peptone: Provides nitrogen, amino acids, and peptides
Glucose: Readily fermentable carbohydrate source
Dipotassium Phosphate (K₂HPO₄): Buffering component
Agar: Solidifying agent

The final acidic pH (approximately 5.5) is critical for selectivity and suppresses most non-aciduric background flora.

Typical Characteristics

Medium Properties

Appearance (dehydrated): Light beige to pale orange powder
Appearance (prepared): Amber to orange-tinted agar
pH (prepared medium): 5.5 ± 0.2 at 25 °C (critical)
Selectivity: Aciduric microorganisms
Differential: No

Composition

Standard Formula (per litre)

Orange Serum (solids equivalent to 200–250 mL fresh orange juice): 4.0–5.0 g
Yeast Extract: 3.0 g
Tryptone / Peptone: 10.0 g
Glucose: 4.0 g
K₂HPO₄: 3.0 g
Agar: 17.0 g

Typical Applications

Fruit Juice & Beverage Microbiology

Total viable count in orange, lemon, grapefruit, and mixed fruit juices
Quality control of concentrates, syrups, cordials, and carbonated beverages

Spoilage Microorganism Detection

Lactic acid bacteria (Lactobacillus, Leuconostoc)
Acetic acid bacteria (Acetobacter, Gluconobacter)
Heat-resistant spoilers (Alicyclobacillus)
Yeasts (Zygosaccharomyces, Candida)
Moulds (Penicillium, Byssochlamys)

Preparation Instructions

Medium Preparation

Suspend 41.0 g of dehydrated medium in 1 L purified water
Heat with frequent agitation and boil for 1 minute
Autoclave at 121 °C for 15 minutes
Cool to 45–50 °C
Pour into sterile Petri dishes

Incubation Conditions

Recommended Conditions

Incubation temperature: 30 ± 1 °C
Incubation time: 3–5 days
Some laboratories incubate at 25 °C for enhanced mould recovery

Interpretation of Results

Typical Colony Appearance

Lactic acid bacteria: Small, round, white to cream colonies
Acetobacter / Gluconobacter: Tiny, opaque colonies; may show clearing zones
Yeasts: Large, smooth, creamy colonies
Moulds: Filamentous mycelial growth with characteristic pigmentation

Storage & Stability

Storage Conditions

Prepared plates: Store at 2–8 °C in sealed packaging
Shelf life (prepared plates): Use within 4 weeks
Do not use plates showing dehydration, contamination, or pH drift

Intended Use

Regulatory Statement

For fruit-juice, soft-drink, and beverage microbiology testing only.

Not intended for medical, veterinary, or food consumption purposes.

Quality & Supply Assurance

Manufacturing & Documentation

Manufactured under controlled conditions
Meets ISO and IFU performance expectations
Certificate of Analysis (COA) available upon request
Technical support provided by Ausamics Life Science

Reference

Standards & Literature

Hays (1951)
Murdock et al. (1952)
IFU Method No. 3
ISO 13681:1999

Customs & Trade Information

Classification

HS / AHECC Code: 3821.00.00
Prepared culture media for development or maintenance of microorganisms