Edible Drinking Straws: A Sustainable Zero-Waste Solution for the Circular Bioeconomy

The plastic pollution crisis facing the globe has put single-use plastics (SUPs) at the forefront of the most important issues of the 21st century. [1] Among the plastic waste contributing to the problem are plastic drinking straws. Though they may seem insignificant, plastic drinking straws are a major cause of marine pollution. This is due to the non-biodegradable properties of plastic materials. Petroleum-based plastics such as polypropylene can remain on the Earth for centuries. [2] They can break down into microplastics that get into the food chain. However, the use of paper and polylactic acid (PLA) straws has been proposed as a replacement. However, they have been criticized on the grounds of poor mechanical properties. This has given edible drinking straws the impetus as a zero-waste material. This is a green chemistry approach to solving the problem. Plastic straws are one of the most common marine pollutants, which can take 300 to 500 years to decompose completely. The presence of plastic straws in the ocean is highly harmful to the biodiversity of the ocean, as research studies have shown that at least 14 species of cetaceans, 7 species of turtles, 20 species of seals, and 56 species of sea birds get trapped with a huge amount of plastic. The chemical compounds present in the plastic are ingested by the body of the animal, which poses a health hazard for the marine animals. The seriousness of the problem can be understood from the fact that, for instance, the consumption of plastic straws was recorded at 10,528 million tons in 2019 in Indonesia [3] The ecological footprint of edible straws is largely defined by the product's position as a "zero-waste" product that seeks to address the long-standing inability of traditional single-use plastics to perform. Unlike the petroleum-based polypropylene straws that take over 200 years to degrade into microplastic fragments that contribute to the degradation of the environment, edible straws are made from edible biopolymers that degrade in a matter of hours to days in the environment. This quick degradation rate eliminates the chance of the straws being ingested by marine life. [4] Additionally, the edible straws' environmental profile is superior to that of the paper or polylactic acid-based straws. Unlike the edible straws, the paper straws undergo an intensive chemical bleaching process that is environmentally unfriendly. Similarly, the PLA straws require the straws to undergo a high-temperature composting process that is environmentally unfriendly. The edible straws' production is environmentally friendly as it is derived from renewable agricultural resources or agri-food waste. This means that the edible straws' use eliminates the chance of the straws' waste management after use. Edible packaging can be a revolutionary technology that makes use of bio-based polymers such as proteins, polysaccharides, and lipids to create packaging that can be consumed along with the food product, hence eliminating waste generation. Such packaging solutions can be categorized as circular bioeconomy solutions since they make use of by products such as cassava pulp, rice bran, and seaweed that can be converted into useful packaging solutions instead of being discarded. Apart from waste reduction, the straws can be enriched with nutrients such as sea grape that can offer essential antioxidants to the consumer, hence becoming a health-beneficial product. [5] Such an approach can shift the focus from consumption to a sustainable product that can contribute to the development and conservation of the seas and the community that depends on them. Composed from a synergistic mixture of food-grade biopolymers such as starches (corn, rice, and potato), proteins (gelatin and gluten), and natural plasticizers, these food-grade straws offer a functional advantage that goes beyond the simple transportation of liquids. The addition of hydrocolloids and lipids gives these food-grade straws greater mechanical properties and water resistance, such that they remain "soggy-resistant" during use. [6] In addition to their environmental advantages, these food-grade straws offer a unique opportunity for functional food development that goes beyond the simple consumer experience. The review discusses the current status in food-grade straw technology, highlighting the choice of materials and formulations, and the physicochemical challenges associated with replacing conventional plastics with food-grade alternatives.

MATERIAL COMPOSITION

The structural integrity and performance potential of edible straws are fundamentally dictated by their material composition. Contrary to petroleum-based plastics such as Polypropylene, which utilize stable synthetic polymers, food-grade biopolymers in edible straws need to balance the rates of biodegradation and hydro stability.

1.Starch-Based Biopolymers:

​The recent literature has identified starch-based biopolymers as the most "future-proof" material for straw production due to their availability and cost-effectiveness. Nevertheless, the source material plays an important role in determining the performance of the straw material in liquids.

• ​Corn Starch (Maize): Still the best material for rigidity. Recent literature has identified corn starch as the material with the least hydrophilicity and swelling ability (less than 20% even after 2 hours of soaking). Additionally, corn starch is identified as the best material for the production of "reusable" straws that can be dried and reused up to 4 times.
• ​Rice Starch: Though rice starch offers a better sensory experience for the consumer, it has been identified as a material with a high swelling index (up to 117%). In trends for rice starch research, the material is no longer used alone but is often blended with rice bran or cellulose fibres to act as a skeleton that prevents the straw from collapsing. [7]
• ​Cassava Starch (Tapioca): This material is often preferred for producing straws due to their excellent film-forming ability. The material is often blended with SPI to produce a material that is flexible like traditional plastics [8]