Impact of retort process on characteristics and bioactivities of herbal soup based on hydrolyzed collagen from seabass skin

Impact of retort processing on the characteristics and bioactivity of herbal soup, based on hydrolyzed collagen from seabass fish skins, as sterilized health drink in glass bottles, was investigated. Retort processing was conducted at either 115 °C or 121 °C for 5, 7, 9 or 11 min (F 0 values) and compared to no retort processing. All retort processing conditions yielded sterile soups, but some differences in moisture content, pH, viscosity, UV-absorbance, browning index, fluorescence intensity, color, α-amino group and total reducing compound contents were observed, compared to those without retort processing. Retort processing enhanced antioxidative activity of herbal hydrolyzed collagen (HHC) soups, regardless of conditions. HHC soups with F 0 value of 7 at 115 °C (115/7) and 121 °C (121/7) showed significantly higher ABTS and DPPH radical scavenging activities, ferric reducing antioxidant power and H 2 O 2 scavenging activity, compared to others. Retort processing had no significant (p > 0.05) effect on the appearance, color, odor, viscosity, flavor, taste and overall perception of HHC soups. The 115/7 and 121/7 samples stimulated cell proliferation and enhance collagen production of L929 mouse fibroblast cells. It was therefore concluded that retort processing could be used for preparing sterilized HHC soup as a ready-to-serve functional drink that is both healthy and safe.

Introduction

The growing demand for medicinal plants and herbs as healthy food supplements, health drinks and tonics have fueled the development of numerous products enriched with bioactive components. Traditional herbs have been used from time immemorial in health care in China and many other countries especially in Asia including Thailand. Herbal products with health benefits are sold in several forms including tablets, tea, liquid extracts and soups (Ekor 2013). Many soups and water extracts are commercialized and marketed as diet supplements and health foods and many herbal soups are considered as bioactive functional foods. Maillard reaction products (MRPs) and the formation of colloidal nanostructures of self-assembling single molecules extracted from plants and the flesh of animals generally occur during the preparation of these soups due to extended boiling. These reactions have been shown to affect the chemical compositions and bioactivity of herbal soup (Ke et al. 2012).

With increasing consumer demand for health promoting foods and drinks, fish protein hydrolysate has been shown to be important because of its nutracuetical properties and Thiansilakul et al. (2007) and Gómez-Guillén et al. (2011) produced fish skin hydrolysates with bioactivity. To enhance bioactivity of fish skin hydrolysate, Karnjanapratum et al. (2016) employed the Maillard reaction and the resulting hydrolysate showed increased antioxidative activity. Benjakul et al. (2017; 2018) developed seabass skin hydrolyzed collagen (HC), with negligible fishy odor, using enzymatic hydrolysis. To increase its nutraceutical value in herbal soup, selected herbs could be used as the source of active compounds to supplement the peptides in the hydrolysate. Several herbs are rich in phenolic compounds, which have been known to possess a wide range of bioactivities, particularly antioxidant activity. Radicals generated can cause a number of diseases. The intake of drink rich in polyphenols has been considered to prevent several diseases such as cancer, neurodegeneration and inflammation (Halliwell 2006; Huang et al. 2010; Ferguson 2010). Hydrolysate from fish skin has been proven to nourish the skin via the induction of fibroblast cell proliferation and collagen production (Benjakul et al. 2018). Thus, the development of herbal soup containing hydrolyzed collagen could bring about the nutraceutical product for health and skin care.

Retort processing is a major preservation techniques widely used in thermal processing for shelf-life extension of foods particularly in the production of ready-to-serve products (Gokhale and Lele 2012). A sterilization temperature above 100 °C is used for production of low acid foods in hermetically sealed containers and in a pressure cooker. Temperatures usually range from 110 to 121 °C, depending on the pressure used and the type of product. Sterilization is generally carried out at 121 °C but the temperature of 115 °C is commonly used for heat sensitive material (Heinz and Hautzinger 2007). Therefore, the retort conditions must be optimized for specific products. An effective thermal process could be designed by varying the sterility level using different times (F0) and temperatures. Nevertheless, thermal conditions could affect the taste, appearance and nutrition as well as bioactivity of final products (Majumdar et al. 2015). Therefore, it is necessary to determine the optimum conditions to ensure the safety, nutritive value and bioactivity of each product.

The objective was to produce soup that had high nutritional content, derived from healthy natural sources, which are safe to eat. To achieve this objective the physical, chemical, sensory and antioxidative characteristics of herbal soup based on seabass skin HC, produced under different retorting conditions was studied. In addition the effects of the soups prepared from different retorting conditions were tested on cell proliferation and collagen production enhancement in an in vitro cell culture system.