The effect of convective heating and microwave heating on antioxidant enzymes in pooled mature human milk

Continuous flow microwave heating and sterilization for liquid food

Continuous flow microwave sterilization for liquid food has advantages of a short time and high retention rate of nutrients. However, uneven microwave heating is the critical factor restricting the industrialization of microwave sterilization. This paper reviews the up-to-date research on the continuous flow microwave heating and the continuous flow microwave sterilization system for liquid food. The causes of the non-uniformity of continuous flow microwave heating are thoroughly discussed and the methods of improving the uniformity are proposed. Finally, the recommendations for future research of continuous flow microwave sterilization for liquid food are presented.

Effect of microwave and convection heating on selected nutrients of human milk

The aim of this study was to determine the influence of the microwave heating method (MWH) on selected determinants of the nutritional value of human milk (HM) and compare to the effect exerted by the standard convection heating (CH) method, including holder pasteurization (HoP). It was showed that using MWH under conditions assumed to ensure microbiological safety, changes in the level of the nutrients were not observed. In these conditions concentration of fatty acids (FAs), lipid peroxides (LP) and α-lactalbumin (α-La) were on a similar level as in raw milk, and furosine was not formed. MWH treatment of HM led to slight increase in the malonaldehyde (MDA) and protein carbonyls (PC) content. However, MDA content in HM as a result of MWH was lower than after application CH.

Nutrients and Bioactive Components of Human Milk After One Year of Lactation: Implication for Human Milk Banks

OBJECTIVE

Specifying the nutrient content and bioactive compounds in milk from long-term lactation for the purpose of finding additional sources of donors' milk for human milk banks.

METHOD

Human milk samples were collected from 43 mothers of term infants (term infant human milk, TIHM) (3-6 weeks of lactation) and 50 mothers who have breastfed for over a year (long-nursing human milk, LNHM). The milk collection time was 24 hours. The analyses of fat, protein, carbohydrate and energy content were performed with human milk analyzer MIRIS (Miris HMA™ ); lactoferrin and vitamin C content using high performance liquid chromatography in reversed phase (RP-HPLC); total antioxidant activity (TAC) and lysozyme by enzyme-linked immunosorbent assay (ELISA); and the activity of glutathione peroxidase (GPx) and catalase (CAT) via spectrophotometric methods. Sociodemographic characteristics of both groups of mothers have been compiled.

RESULTS

Higher fat content and energy value was found in LNHM than in TIHM. Protein content in LNHM and TIHM did not differ. Carbohydrate content was lower in LNHM than in TIHM. TAC, CAT and GPx activity were higher in LNHM compared to TIHM. No significant differences in the content of lysozyme, lactoferrin and vitamin C between the studied groups were found.

CONCLUSIONS

The findings suggest that after 12 months of lactation, human milk still has significant nutritional value, does not lose bioactive components and can be considered for use in human milk banks.

Effect of convection and microwave heating on the retention of bioactive components in human milk

Bioactive substances are very important components of human milk (HM), especially for premature newborns. The effects of convection (CH) and microwave heating (MWH) at 62.5 and 66 °C, on the level of selected bioactive components of HM: lysozyme (LZ), lactoferrin (LF), secretory immunoglobulin A (sIgA), basal lipase (BL), cytokine TGF-2, vitamin C and total antioxidant capacity (TAC) was compared. Regardless of the used heating methods the TAC of HM, determined by TEAC and ORAC-FL assay, proved to be insensitive to temperature pasteurization, in contrary to BL. MWH in the conditions of 62.5 for 5 min and 66 °C for 3 min are ensuring microbiological safety with a higher retention of most of the tested active HM proteins compared to CH. Only in the case of LZ the MWH had a more degradative effect on its concentration. Controlled conditions of MWH preserve the bioactive components of the HM better than CH.

The Effect of Pasteurization on the Antioxidant Properties of Human Milk: A Literature Review

High rates of oxidative stress are common in preterm born infants and have short- and long-term consequences. The antioxidant properties of human milk limits the consequences of excessive oxidative damage. However, as the mother's own milk it is not always available, donor milk may be provided as the best alternative. Donor milk needs to be pasteurized before use to ensure safety. Although pasteurization is necessary for safety reasons, it may affect the activity and concentration of several biological factors, including antioxidants. This literature review describes the effect of different pasteurization methods on antioxidant properties of human milk and aims to provide evidence to guide donor milk banks in choosing the best pasteurization method from an antioxidant perspective. The current literature suggests that Holder pasteurization reduces the antioxidant properties of human milk. Alternative pasteurization methods seem promising as less reduction is observed in several studies.

Neurotrophic Factors in Human Milk in Early Lactation and the Effect of Holder and Microwave Pasteurization on Their Concentrations

OBJECTIVES

The objective of this study was to determine the level of brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) in human milk in the first 2 weeks of breast-feeding and compare the effects of Holder pasteurization (HoP, 62.5 °C, 30 minutes) and microwave pasteurization (MP) at constant temperature (62.5 °C) on the concentraion of both neurotrophic factors (NFs).

METHODS

Concentration of NFs in human milk was determined using a commercially available ELISA assay.

RESULTS

The average concentration of BDNF and GDNF in milk was 11 ± 6 ng/mL and 336 ± 238 pg/mL, respectively. There was a positive correlation between the concentrations of BDNF and GDNF in human milk and day of lactation (r = 0.441, P < 0.05 and r = 0.482, P < 0.05, respectively). In addition, there was a significant correlation between the levels of BDNF and GDNF (r = 0.366, P < 0.05). HoP and MP for 10 minutes affected both NF levels similarly, causing degradation of BDNF by about 24% and 17%, and GDNF by 47% and 45%, respectively. Use of MP for 5 minutes resulted in preservation of nearly 91% BDNF and 79% GDNF in human milk.

CONCLUSIONS

In the pasteurization processes carried out, results showed that GDNF is more susceptible to degradation under the influence of high temperature. To the authors' best knowledge, this is the first study evaluating the effects of HoP and MP at constant temperature on the concentration of NFs in human milk. It was found that the MP for 5 minutes is the optimal method.

Innovative Techniques of Processing Human Milk to Preserve Key Components

Human milk not only contains all nutritional elements that an infant requires, but is also the source of components whose regulatory role was confirmed by demonstrating health-related deficiencies in formula-fed children. A human milk diet is especially important for premature babies in the neonatal intensive care unit (NICU). In cases where breastfeeding is not possible and the mother's own milk is insufficient in volume, the most preferred food is pasteurized donor milk. The number of human milk banks has increased recently but their technical infrastructure is continuously developing. Heat treatment at a low temperature and long time, also known as holder pasteurization (62.5 °C, 30 min), is the most widespread method of human milk processing, whose effects on the quality of donor milk is well documented. Holder pasteurization destroys vegetative forms of bacteria and most viruses including human immunodeficiency virus (HIV) herpes and cytomegalovirus (CMV). The macronutrients remain relatively intact but various beneficial components are destroyed completely or compromised. Enzymes and immune cells are the most heat sensitive elements. The bactericidal capacity of heat-pasteurized milk is lower than that of untreated milk. The aim of the study was for a comprehensive comparison of currently tested methods of improving the preservation stage. Innovative techniques of milk processing should minimize the risk of milk-borne infections and preserve the bioactivity of this complex biological fluid better than the holder method. In the present paper, the most promising thermal pasteurization condition (72 °C-75 °C,) and a few non-thermal processes were discussed (high pressure processing, microwave irradiation). This narrative review presents an overview of methods of human milk preservation that have been explored to improve the safety and quality of donor milk.