‘Natural’ barriers to shelf-life extension
As more people are dining at home, time-strapped consumers are relying increasingly on prepared or partially prepared proteins that they can finish quickly in the kitchen. Shoppers also are weary of meat spoilage, and manufacturers now want to be twice as sure that their product is safe.
In addition, the current market structure also imposes longer times in storage and distribution systems. All these factors contribute to the demand for shelf-life extension ingredients for proteins, says Kantha Shelke, principal at Corvus Blue LLC, Chicago.
Consumer demands for clean labels — derived from their distrust of chemical-sounding additives — are driving new ingredient technologies as antimicrobial interventions. These are largely plant extracts, especially herbs, spices, extracts and essential oils, Shelke says. Currently many consumers believe that natural extracts are somehow more effective and better than chemical preservatives, she explains.
The antimicrobial properties of plant extracts and soluble spices are attributed to their polyphenols, Shelke explains. For example, rosemary extract is rich in phenols that can extend the shelf-life by its antimicrobial properties and help stabilize the color of meat products by acting as an antioxidant.
Plant extracts’ antimicrobial properties are influenced by temperature, relative humidity, initial bacterial load and their intrinsic chemical properties, such as pH and polarity.
“It is critical to ensure that the chosen extract or spice effectiveness matches the pH of the protein product,” Shelke says. Fat affects antimicrobial effectiveness as well.
“In general, effectiveness decreases with increase in fat content,” she says.
Combinations of plant extracts are more effective than single plant extracts. For example, a sage, rosemary and green tea extract combination or orange or lime powder with rosemary extract in a clean-label vinegar can extend the shelf-life of ground poultry sausage and whole-muscle poultry products better than each of the individual ingredients used singularly, Shelke says. This is due to the combination of antimicrobial and antioxidant activities, she explains.
Spice/herb extracts proven in research and in commercial blends as shelf-life extension ingredients include: cinnamon, rosemary, paprika, mustard, oregano, sage, green tea and grape seed. All of these ingredients have antimicrobial properties, but their limiting factors include being more effective in laboratory media than in commercial food products, and the levels at which they are effective also often affect sensory quality negatively, Shelke says. In addition, plant extracts and spices that are effective as an antimicrobial surface treatment do not perform as well in ground products. Plant extracts also are generally not as effective as the individual active components, she adds.
Plant extracts’ application in poultry and meat products is a function of the process by which the product is manufactured along with its shape, size, how it is distributed and how it is eventually prepared before consumption.
“With use of any natural ingredient or ingredient extracts for antimicrobial treatment, one should consider suitability to process, cost effectiveness and sensory effect,” Shelke says.
For example, clove oil in chicken frankfurters — as a surface and inclusion application — can reduce Listeria growth without significantly influencing flavor, she explains. Herb extracts are effective as surface decontamination agents against E. coli O157:H7, Salmonella typhimurium, and Listeria monocytogenesin beef trimmings and pieces, but are not as effective in ground beef and chicken, Shelke says.
Conventionally, organic acids, vinegar, sodium diacetate, and sodium or potassium lactate are effective antimicrobials in the poultry industry to extend the shelf-life of fresh poultry sausage or marinated poultry. For clean labels, citrus and commercial vinegar products can be used along with plant extracts, such as rosemary, sage, green tea, paprika and oregano, in various combinations, as a hurdle approach to control spoilage and pathogenic microorganisms, Shelke says.
Although processors will try to respond to consumer demand for natural shelf-life extending ingredients with plant-derived materials, these products will not serve as a silver bullet.
“The industry will most likely investigate new processing technologies such as cold plasma and ionized gases to extend the shelf-life of protein foods,” Shelke says. “Additionally, there are not enough herbs and spices in the world to provide the amount of extracts and bioactive compounds for shelf-life extension. Processors will, therefore, seek synthetic analogs and nature identical compounds along with microbiological strains that can be fine-tuned to their functionalities.”