Effect of Heat Treatments on the Constituents of Camel Milk

Arab Khan Lund1*, Atta Hussain Shah2, Gul Bahar Khaskheli2, Mool Chand Malhi3, Ahmed Sultan Jatoi4, Abdul Samad Mangsi5 and Asad Ali Khaskheli6

1Department of Meat Technology, Shaheed Benazir Bhutto University of Veterinary and Animal Sciences, Sakrand-67210

2Department of Animal Products Technology, Sindh Agriculture University, Tandojam

3Department of Animal Physiology, Sindh Agriculture University, Tandojam, Pakistan

4Department of Poultry Production, Shaheed Benazir Bhutto University of Veterinary and Animal Sciences, Sakrand-67210, Pakistan

5Department of Dairy Technology, Shaheed Benazir Bhutto University of Veterinary and Animal Sciences, Sakrand-67210

6Department of Animal Nutrition, Shaheed Benazir Bhutto University of Veterinary and Animal Sciences, Sakrand-67210, Pakistan.

ABSTRACT

Heating is an essential step in the dairy industry. This study was carried out in order to observe the influence of heating and time combinations (63°C/30min; T1, 72°C/15sec; T2 and 100.17°C/10min; T3) on physical and chemical characteristics of camel milk. The physical characteristics; pH value, acidity, specific gravity, viscosity (cP) and chemical constituents; ash, casein number (CN), non-casein (NCN), whey protein nitrogen (WPN) and whey protein denaturation (WPD) were significantly (p<0.05) varied at different heat treatments in contrast to control (T0). The variation was also observed in conductivity, refractive index, moisture, fat, protein and lactose content, however, it was non-significant (p>0.05). Results are concluded that the nitrogen fractions markedly affected by different heating and time combinations followed by physical properties while less effect on the chemical components of milk ultimately nutritive value.

Article Information

Received 22 April 2019

Revised 23 May 2021

Accepted 03 June 2021

Available online 02 November 2021

(early access)

Published 26 April 2022

Authors’ Contribution

AKL conducted the experiment and wrote the manuscript. AHS, GBK and MCM supervised the research, designed the experiment and guided. ASJ and ASM supported in the analysis of research data and reviewed the final manuscript. AAK helped in conducting experimental work and data collection.

Key words

Thermal stability, Camel milk constituents and nitrogen fractions

DOI: https://dx.doi.org/10.17582/journal.pjz/20190422190446

* Corresponding author: aarabbaloch@gmail.com

0030-9923/2022/0004-1999 $ 9.00/0

Copyright 2022 by the authors. Licensee Zoological Society of Pakistan.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

Camel population is about four million throughout the world. Pakistan ranks 8th with a population of about 1 million and mostly populated with dromedaries but a few herds of Bactrians (two-humped camels) are also found in the extreme northern areas (FAO, 2010). They are an important nutritional source for inhabitants in arid and semi-arid areas throughout the world. Globally, camel milk has been exploited for human health due to its nutritional and therapeutic properties (Gader and Alhaider, 2016). It has higher amounts of essential fatty acids (Shamsia, 2009), antimicrobial factors (i.e. lysozyme, lactoferrin, lactoperoxidase and immunoglobulins, antibacterial and antiviral protective proteins) and insulin-like protein which made it superior to the milk of other animals (Yadav et al., 2015).

Heat treatments (i.e. pasteurization, boiling and sterilization) are being practiced to increase the keeping quality and make it hygienic for human consumption (Walstra et al., 2005). People prefer to consume camel milk because it acts as anti-carcinogenic (Magjeed, 2005), hypo-allergic and anti-diabetic (Shabo et al., 2005). The knowledge regarding the influence of these treatments on the nutritional, biological and functional properties of has been studied but still knowledge scared on camel milk. Therefore, the present study was designed to evaluate the influence of various heat treatments on physico-chemical characteristics and the nitrogen fractions of camel milk.

Materials and methods

The raw camel milk was procured from the vicinity of Hyderabad, Sindh-Pakistan and brought to the Laboratory, Department of Animal Products Technology, Sindh Agriculture University, Tandojam. The camel milk was categorized as T0, T1, T2, and T3 (control/raw, heat treated at 63ºC for 30minutes; LTLT, 72ºC for 15 seconds; HTST and 100.17ºC for 10 minutes; boiling, respectively). All milk samples were analysed for physico-chemical characteristics and nitrogen fractions.

Physical properties include titratable acidity, specific gravity, viscosity (cp) and conductivity (ms/cm) of raw and heat treated camel milk was determined as reported in the Association of Official Analytical Chemists (AOAC, 2000). The pH value and Refractive Index of samples were analyzed by using a pH meter (Model-1 Hanna Instruments, Italy) and a refractometer (Model RX-5000a, Tokyo, Japan), respectively.

The chemical constituents such as moisture and ash content were determined as described by AOAC (2000), the fat content was analysed by the Gerber method as described by James (1995) and the protein content was estimated according to the method of British Standards Institution (BSI, 1990). Lactose percentage was determined by the difference formula James (1992). Nutritive value was calculated by the formula as reported by James (1995).

Among nitrogen fractions, total nitrogen (TN) in camel milk (heated and non-heated) was analysed according to method as reported by Ling (1987). Non-casein nitrogen (NCN) was analysed according to the method as described by Abbas et al. (2013). Non-protein nitrogen (NPN) was determined according to a method as mentioned by Abbas et al. (2013). Whey protein nitrogen (WPN), casein number (CN) and denaturation of WPN were determined according to the methods as used by Manji and Kakuda (1987).

The data so obtained was analysed by using Analysis of Variance (ANOVA) and least significant difference (LSD) at 5% probability through the computerized statistical package, Student Edition of Statistix (SXW), Version 8.1 (Copyright 2005, Analytical software-USA) (Gomez and Gomez 1984).

Results and discussion

The current study revealed that the physical characteristics (Table I) of camel milk were significantly (P<0.05) changed by applying different heat treatments except for conductivity and refractive index where the differences existed non-significant (P>0.05). The pH value and acidity have an inverse relationship and showed significant (P<0.05) variations. These results

Table I. Effect of heat treatments on the characteristics of camel milk.

* Values having different superscripts within the row are significantly different from one another. T0­ (control/raw), T1 (heat treated at 63ºC for 30minutes; LTLT), T2 (72ºC for 15 seconds; HTST) and T3 (100.17ºC for 10 minutes; boiling). NS=non-significant, NV=nutritive value.

are in line with the findings of Alkaladi et al. (2014) who reported that the pH of milk slightly increased with heat treatments (pH 6.5 at 63°C 30min and 6.4 of control milk). The specific gravity and viscosity also have an inverse relationship and significantly (P<0.05) varied at T1 and T3 and non-significant at T1 than that of control (T0). It is of importance to note that the heating of milk causes evaporation of moisture while enhancing the proportion of total solid that makes it more viscous and resulting in the increase of specific gravity. It was also found the changes in conductivity and refractive index but were non-significant, (P>0.05).

In the current study, the effect of various heat treatments on chemical components (Table I) such as moisture, fat, protein and lactose contents of camel milk was found to be non-significant (P>0.05), except for ash contents where differences existed significant (P<0.05) in contrast to control (Table I). The ash contents are in ranges with the findings of Khanna and Rai (1993). However, a slight variation was observed in all components of camel milk due to the evaporation of water under different temperature regimes. The nutritive value (Table I) of the milk was increased non-significantly (P>0.05) under different heating and time combination.

The heating along with time combination had a significant (P<0.05) effect on nitrogen fractions (Table I) except total nitrogen (TN) and non-protein nitrogen (NPN) that were varied non-significantly (P>0.05) than that of control. The total nitrogen was also unchanged in the study carried out by Hattem et al. (2011). Denaturation of whey protein increased significantly (P<0.05) with the increasing temperature and time combinations. Furthermore, researchers reported that the NCN and WPN decrease with the heating (Hassan et al., 2009) while casein number and denaturation of whey protein increases under heat treatments (Farah, 1986).

Conclusion

The conclusion of the present study is that the heating and time combination has great influence on the nitrogen fractions and physical properties while insignificant effect observed on the chemical constituents of camel milk.

Statement of conflicts of interest

The authors have declared no conflict of interest.

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