Formulation of pasteurized ready-to-feed (RTF) infant formula enhanced by adding bioactives: a new product development (NPD)

Abstract

Infant Milk Formula (IMF) is a designed food and serves as a substitute for human milk for infants under 12 months of age. Currently available ready-to-feed (RTF) formula is a sterilized product and processed by Ultra High Temperature (UHT) to ensure safety. However, thermal treatment has severe impacts on colour, flavour, vitamin and protein of treated products. On the other hand, pasteurization is a mild processing which retains the maximum nutrients in compliance with safety standards, although it suffers from short shelf life of the treated product in refrigerated condition. Therefore, this thesis evaluated the scope to come up with a pasteurized RTF formula fortified with bioactive proteins using both thermal and High Pressure Processing (HPP). HPP was initially adopted as a non-thermal technology to process food with its proven feature of microbial inactivation while maintaining the organoleptic attributes of treated products. However, currently, it is widely used in food modification through understanding molecular arrangements and ingredient (protein) denaturation. Retention of lactoferrin (LF) was evaluated under conventional thermal (63-90 ºC) treatments and compared with HPP (300-600 MPa) applied at ambient temperature. A very high degree of LF retention (> 90%) was observed at High Temperature Short Time (HTST) conditions, whereas HPP treatments retained only 66-83% LF. Furthermore, LF remarkably maintained its iron-binding capacity and storage stability after HTST pasteurization indicating the suitability of conventional HTST pasteurization to treat LF-added RTF liquid IMF. Subsequently, the effects of HPP (300- 600 MPa) at ~ 20-40 °C and HTST pasteurization were investigated and compared in the retention of alpha-lactalbumin (α-Lac) and beta-lactoglobulin (β-Lg). β-Lg is a major whey protein of cow milk (3-4 g/L) whereas, interestingly, it is not present in human milk. It is also considered as a prime reason for cow milk allergy to infants. Moreover, total protein content in IMF (15 g/L) is much higher than human milk (9-11 g/L), and such an excessive protein in IMF introduces paediatric obesity. In this aspect, to modify protein composition, the highest ratio of α-Lac to β-Lg was achieved after HPP (600 MPa for 5 min applied at 40.4 °C), which potentially explains the synergistic effect of HPP and heat. Due to the substantial denaturation of β-Lg in treated IMF, HPP at elevated temperature showed the pathway to manufacture a pasteurized RTF hypoallergenic and low protein IMF, a new product for niche marketing. This study investigated further the effect of HPP on LF retention along with an aim to obtain a high ratio of α-Lac to β-Lg in IMF. Pressure Assisted Thermal pasteurization (PATP), a novel approach, was achieved from HPP of 600 MPa for 15 s applied at 60 °C to attain 72.3 °C after pressurization. Retention of LF after HTST and PATP was > 90% and > 75%, respectively suggesting 20-30% overrun of LF during PATP. In contrast to HTST, the highest ratio of α-Lac to β-Lg was observed in PATP-treated IMF. However, both HTST and PATP showed > 5 log inactivation of E. coli (ATCC 8739) in IMF. Therefore, this study confirmed a route to develop a PATP-processed hypoallergenic and low protein RTF formula, a niche product. Additionally, for the first time, denaturation kinetics and storage stability of osteopontin (OPN) was investigated. OPN is a multifunctional bioactive protein and recently extracted from cow milk. OPN concentration in human milk (138 mg/L) is very high compared to cow milk (18 mg/L) and IMF (9 mg/L) and therefore, recommended for use as a supplement in IMF. A rapid and robust Reversed-Phase HPLC method was developed and validated to measure OPN in IMF, which could be used in other food and dairy products. Denaturation kinetics with very high storage stability of OPN revealed the suitability of thermal processing of OPN-added IMF while HPP was recommended to apply at < 500 MPa at ambient temperature. This thesis evaluated the possibility to come up with a pasteurized RTF formula fortified with bioactive proteins using both thermal and HPP technologies. The outcome of this research will help to formulate more functional IMF through proper selection of bioactive ingredients and processing parameters in mitigating the challenges in process and product development.