Production and application of freeze dried biocomposite coating powders from sunflower oil and soy protein or whey protein isolates
Introduction
Edible coating technology is widely accepted and has been practiced for a long time to improve food safety and increase shelf life by acting as a barrier against moisture and gas. The main components of edible coatings are carbohydrate, protein and/or lipids (Zhang, Liu, Yong, Qin, Liu, & Liu, 2019). Polysaccharides and proteins ensure polymer interaction and show good mechanical features. Nevertheless, due to their hydrophilic structures, they cannot resist the water vapor transition. On the contrary, lipids form an effective barrier to water vapor transmission as they have hydrophobic characteristics and are effective to reduce weight loss due to dehydration during storage. When a lipid is used alone as a coating material, it shows a fragile structure, and also some problems may be induced such as off-flavor and/or peel pitting in fruits (Rojas-Argudo, Del Río, & Pérez-Gago, 2009). Composite formulations can be used to take advantage of the strengths of all components. Numerous researches are about preparing edible coating materials, improving their characteristics by using different sources such as essential oil and/or functional food additives, and examining their applications on food products (Fagundes et al., 2015, Nawab et al., 2017). To the best of our knowledge, no studies exist in the literature on biocomposite coating powder production and evaluation of their properties. In comparison to liquids, powders possess a broader spectrum of applications due to their longer shelf-life, higher stability, easier transportation, and storage and therefore lower cost (Hettiarachchi, Voronin, & Harte, 2019).
In this study, two different protein sources, soy protein isolate (SPI, vegetable origin) and whey protein isolate (WPI, animal origin) were used in combination with sunflower oil (SO, vegetable oil). SPI is an abundant, cost-effective, high-nutritional material and it is suitable for producing homogeneous biodegradable coatings with good barrier and mechanical properties (Galus, 2018). Also, WPI is a by-product of the cheese industry and it consists on at least 90% of milk globular proteins, essentially α-lactalbumin and β-lactoglobulins (Norwood, Le Floch-Fouéré, Briard-Bion, Schuck, Croguennec, & Jeantet, 2016). WPI is preferred to be used in the food packaging industry due to its high capacity for gelatinization and good emulsifying properties (Tavares & Noreña, 2019). Sunflower seeds provide a considerable amount of vitamins (especially vitamin E) and found to be rich in minerals. Sunflower oil (SO) has gained importance due to its high content of (PUFAs) linoleic and oleic acids. Baked products such as cake are highly preferred all over the world due to their taste and soft texture. Cakes are mainly characterized by a porous structure and high volume, which confers a spongy texture (Bartolozzo, Borneo, & Aguirre, 2016). Texture properties of cakes, which are directly related to that desired spongy structure, are one of the most important quality parameters so must be controlled to ensure the potential sell of the product. Few types of research exist in the literature have been dedicated to coating of different baked goods to extend their shelf-life and to preserve them from detrimental textural changes (El-Zainy, Aboul-Anean, Shelbaya, & Ramadan, 2014; Saraiva et al., 2016). However, there have been some interesting articles to show the addition of ethanol into the coating formulations used in these studies. If ethanol is not directly used in the bakery product but if it is added to the packaging material, it is not indicated on the label, and the consumer is unaware of its presence. Nutritionists still criticize the use of ethanol as a component or preservative for children, due to its toxic effect and unpleasant odor, even if used in low concentrations and is generally considered as safe in the USA (GRAS) (Melini & Melini, 2018). It was observed in previous studies that the coated bakery samples were generally in small form portions, such as muffins or sweet baked (Bartolozzo et al., 2016, Eom et al., 2018). In this study, it was preferred to use sliced baton cakes. Baton cakes have larger portions, they are eaten as sliced and most of the time cannot be consumed totally after their packages are opened, and therefore their textural distortion risks are much more.
Bearing this in mind, in the present contribution it was aimed to develop and investigate an innovative biocomposite coating powder product ready to use on bakery products with the addition of only water and glycerol but without any preservatives incorporated. SPI and WPI were chosen as the main coating components and combined with three different SO concentrations to obtain different formulations and their various physicochemical properties were analyzed. The solutions were then dried using freeze drying to get composite coating powders. Reconstituted powders were applied on a sliced commercial cake product to evaluate the effect of the coating materials on the cake’s textural properties.
Section snippets
Materials
SPI (protein content > 90%) was obtained by Gushen Biological Technology Group Co., Ltd and WPI (protein content > 90%) was supplied from Davisco Foods International Inc. (BiPRo, Le Sueur, MN., USA). Sunflower oil was purchased from a local market in Gaziantep in Turkey. Glycerol (84–88%) and NaOH (puriss > 98%) were obtained from Sigma-Aldrich (St. Louis, MO, USA).
Preparation of initial emulsions for freeze drying
WPI at 8% (w/v) and SPI at 4% (w/v) were dissolved in distilled water. The pH of SPI solution was adjusted to 10 with 4 N NaOH to
Solid yield, moisture content, hygroscopicity and water activity of freeze dried powder
The physical properties of the powder samples are shown in Table 1. The product yield of all powder samples was found to be more than 93% and there were no significant differences between formulations (p > 0.05). The method of freeze drying has higher costs when compared to other drying processes. However, it offers several positive aspects, such as operating at much lower temperatures compared to other drying methods, being non-contact with air, and low yield loss (Bhatta, Stevanovic Janezic,
Conclusions
A new product of SO incorporated biocomposite coating powder was produced from different protein resources using freeze drying and characterized. Obtained powder samples had at least 93% solid yield and 91% solubility, also all the formulations were wettable. Moisture content, morphology and amorphous structure were not affected significantly by lipid addition (p > 0.05). Incorporation of sunflower oil showed an increasing tendency for enthalpy values and oil usage in formulation caused higher
CRediT authorship contribution statement
Burcu Gökkaya Erdem: Conceptualization, Formal analysis, Writing - original draft, Validation, Investigation. Sevim Kaya: Supervision, Resources, Writing - review & editing, Project administration.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgement
This research project was supported by Technological Research Council of Turkey (TUBITAK) (Project no: 215O068) which led to this paper.
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