Discuss the production and physico-chemical properties of cream. Enumerate the common defects encountered during its manufacture and storage.

Production of Cream

Cream production broadly involves separating the fat from milk. Historically, this was done through gravity settling or centrifugal force using cream separators. Modern techniques are more efficient and precise.

Traditional Methods

• Gravity Settling: Milk is allowed to stand undisturbed for a period, allowing the heavier fat globules to rise to the surface, forming a layer of cream. This is a slow process and yields a lower fat percentage.
• Centrifugal Separation (Early Models): Simple hand-operated cream separators used centrifugal force to expedite the separation process, but were less efficient than modern machines.

Modern Methods

• High-Speed Centrifugation: Modern cream separators utilize high-speed centrifugal force to efficiently separate cream from milk. These machines can adjust the speed and time to achieve desired fat percentages.
• Microfiltration: A membrane-based technique that physically separates fat globules from milk, resulting in a very clean and consistent cream product.
• Directional Precipitation: A relatively newer technique which uses controlled electric fields to precipitate fat globules.

Method	Efficiency	Fat Percentage Control	Speed	Cost
Gravity Settling	Low	Poor	Slow	Low
Early Centrifugal Separation	Moderate	Fair	Moderate	Moderate
High-Speed Centrifugation	High	Excellent	Fast	High
Microfiltration	Very High	Excellent	Moderate	Very High

Physico-Chemical Properties of Cream

The quality and functionality of cream depend on its physico-chemical properties.

• Fat Content: The defining characteristic of cream. Standard cream typically contains 18-36% milk fat. Different grades of cream (e.g., light cream, heavy cream) are defined by their fat content.
• Density: Varies with fat content. Higher fat content leads to lower density.
• pH: Typically ranges from 6.4 to 6.7.
• Viscosity: Influenced by fat content, temperature, and protein content.
• Stability: Cream stability refers to its resistance to separation (creaming). It's influenced by factors like fat globule size, protein content, and presence of stabilizers.
• Color: Determined by carotenoids and riboflavin present in milk.

Common Defects Encountered During Manufacture and Storage

Defects can arise during both cream production and storage, impacting its quality and shelf life. These can be broadly classified into manufacturing defects and storage defects.

Manufacturing Defects

• Insufficient Fat Separation: Caused by improper machine settings or low centrifugal force, leading to a product with lower-than-expected fat content.
• Contamination: Introduction of undesirable microorganisms or foreign matter during processing.
• Over-Separation: Excessive centrifugal force can lead to the separation of proteins along with fat, resulting in a less stable cream.

Storage Defects

• Phase Separation (Creaming): Fat globules coalesce and rise to the surface, leading to a layered appearance. This is due to destabilization of the fat globules.
• Sourness: Growth of lactic acid bacteria, resulting in a sour taste and reduced pH.
• Off-Flavors: Development of undesirable flavors due to enzymatic reactions or microbial activity.
• Color Changes: Oxidation of pigments can lead to discoloration.
• Development of Undesirable Odors: Can be due to rancidity (fat oxidation) or microbial metabolism.

Preventive Measures

• Strict hygiene practices during processing.
• Proper calibration and maintenance of cream separators.
• Temperature control during storage. Refrigeration slows down microbial growth and enzymatic reactions.
• Use of stabilizers (e.g., mono- and diglycerides) to improve cream stability.
• Modified Atmosphere Packaging (MAP) to reduce oxygen exposure and prevent rancidity.
• Regular monitoring of pH and microbial load.