In the intricate world of industrial and food supply chains, starch emerges as a versatile ingredient with a complex composition. Contrary to the perception of starch as a pure entity, its existence is intertwined with various minor constituents. Spanning diverse regions across the globe where starch sources are cultivated, these constituents exhibit variations in both type and quantity. Among the common minor components found in starch are moisture (water), lipids (fats), nitrogen (protein), phosphorus, and trace elements (minerals).
Lipids (Fats): A Fractional Presence
Commercial starches, integral to the food industry, typically contain less than 1% fat. Any levels exceeding this threshold are meticulously extracted or hydrolyzed to maintain quality standards. A small percentage of lipids is believed to be intricately bound within the starch’s amylose/amylopectin configuration. Acid hydrolysis assays reveal this presence, indicating potential associations with internal proteins (Jane et al., 1992).
Protein (Nitrogen): A Variable Component
The protein content in starch is variable, contingent on the starch source. All protein analyses are reported as a percentage of nitrogen. Starches isolated from high-protein flours, such as wheat and barley, undergo separation from the proteinaceous phase. In other starches prevalent in the food industry, protein content typically remains below 1%. Similar to lipids, there is a hypothesis that protein may be structurally bound within the starch granule matrix, rendering it less accessible for simple extraction (Jane et al., 1992).
Phosphorus: The Esterified Presence
Root (tuber) and legume sources of starch exhibit esterified phosphorus in the form of phosphate monoesters, linked to the C-6 and C-3 hydroxyl groups of glucose units. While most cereal starches contain minimal phosphorus, if present, it is often analyzed as phospholipids (Morrison, 1989).
Trace Elements: The Subtle Inclusions
In addition to lipids, proteins, and phosphorus, starch also harbors minute amounts of minerals and inorganic salts, collectively referred to as “ash.” The composition of ash in starch products varies based on their source or origin and the regions of the world where they are produced. Commercial starches typically report an ash content of <0.5% based on a dry starch basis (dsb), also known as “dry solids basis.”
Moisture (Water): The Overlooked Component
Amidst the considerations of starch as a nearly pure carbohydrate, one commonly overlooked component prevails: water. In its native state, the moisture content of starch exhibits significant variability. However, refined starch products destined for the food industry undergo meticulous preparation to ensure a more consistent moisture level. Commercially prepared starch carries an average moisture content of approximately 12.0%, with exceptions ranging from as low as 3.0% (redried) to as high as 18% (native potato) for specific commercial starch products.
In essence, the composition of starch extends beyond its carbohydrate matrix, incorporating an intricate interplay of minor constituents that contribute to its multifaceted nature. Understanding these components becomes pivotal for industries harnessing the diverse applications of starch in various formulations and products.