Moisture regulators can be used within active packaging concept both for moisture absorption or moisture regulation. For example, the control of moisture in cheese is very important for preservation and extending the shelf life by reducing the growth of spoilage bacteria or preventing moisture-mediated oxidation.
The approach being adopted is to use deliquescent salts in packaging materials in order to control the relative humidity (RH). These salts can be used to regulate the RH to a desired value by absorbing water vapor when the RH exceeds a certain value or releasing the absorb water again if the RH subsequently decreases (Muller, 2013). Desiccant films or moisture controlling sachets or pads can be used for a wide range of foods including cheeses (Vermeiren, 1999).
Pantaleao et al. (2007) studied with the development of a packaging system providing the required relative humidity inside the package to extend the shelf life of Saloio cheese (full-fat Portuguese cheese) at 8°C, 85% RH during storage period of 60 days. The packaging system included a PVC (polyvinlychloride) lid over a PS (polystyrene) base where the moisture controlling Humidipak® sachets were placed in it. It was claimed that twoway humidity control is possible with this technology by continually responding and adjusting to the outside RH by either adding or removing water to maintain a predetermined level of RH inside the packages. The sachets consisted of a gelled, saturated solution that was filled into a small sachet made of a material with very high permeability, but not allowing for liquid-water to pass through or leak into the container, and were able to maintain two different levels of RH of 78% and 84%. As a result, no growth was observed for pathogenic or contaminants in Humidipak® sachets and constant hardness was supplied over the storage period, with less weight loss and water loss provided compared to the cheese samples unpackaged or packaged with perforated film.
The latest studies show that the other concept in active packaging is also to make the food products healthier for consumers over consumption. The enzymes can be immobilized or encapsulated in to the food-packaging materials within this concept. A reaction that is considered beneficial from a nutritional point of view can be catalyzed (i.e., decreasing the concentration of a nondesired food constituent, and/or producing a food substance beneficial to the health of the consumer).
In dairy technology, there is a number of trials reporting enzymatically active packages to reduce lactose and cholesterol content of dairy products. The lactase-active package is meant to reduce the lactose content of milk during storage by splitting this complex sugar into glucose and galactose. Similarly, the enzyme cholesterol reductase could be immobilized into polymers to convert cholesterol into coprostanol and coprosterol. The use of this type of packages would allow the production of a value-added food without modifying the manufacturing procedure (Lopez-Rubio et al., 2006; Lopez- Rubio et al., 2008).
Wong et al. (2013) developed an active package in which lactase is covalently bounded to LDPE for in-package production of lactose-free dairy products. The same researchers determined the effect of immobilized-lactase active packaging material on the quality and shelf life of UHT milk (Wong and Goddard, 2014). In this study, results indicated that such active packaging films could allow in-package lactose hydrolysis without adversely affecting product quality. The activity of lactase active packaging film retained after up to 8 weeks and lactase did not migrate and significantly affect the microbial growth.
In some studies, it was shown that beta-cyclodextrins (PCD) incorporated into the packaging materials can be used to reduce the cholesterol content of milk. Lopez-de- Dicastillo et al. (2011) used hydrophilic EVOH films containing (PCD) for active packaging of pasteurized milk and UHT milk stored at 4°C and 23°C, respectively. The presence of active film containing PCD significantly reduced cholesterol concentration in both milk samples. In another study, soy protein isolate (SPI) films reinforced with starch nanocrystals (SNC) and containing different proportions of PCD was used in packaging of milk to reduce cholesterol concentration. PCD acted as an effective cholesterol receptor—as the amount of PCD in the film increased, the amount of cholesterol in milk decreased (Gonzalez and Igarzabal, 2015).