Nutritional and sensory evaluation of soft cheese made from locally sourced coagulants

G A Ibhaze, O A Adebayo and G E Onibi

Department of Animal Production and Health, Federal University of Technology, Akure, Ondo State, Nigeria.
begladalways@yahoo.com

Abstract

Sodom apple (Calotropis procera) is the conventional coagulant used in the production of cheese (Wara) in Nigeria. Unripe Pawpaw fruit extract (PWE), Moringa seed extract (MSE) and Soursop fruit extract (SSE) are alternative coagulants that have not been fully explored. Hence, this study was conducted to evaluate the nutrient and organoleptic properties of cheese produced with these extracts compared with commercially retailed cheese (CRC) and Sodom apple extracted (SAE) cheese. The completely randomized design was adopted. Raw milk was collected from lactating White Fulani cows and divided into four parts of one litre each. The milk was heated to a temperature of 50°C and 100 ml of each extract was added to the milk and heated slowly until boiling was reached. The chemical composition and sensory properties of the cheeses were influenced by the extracts (coagulants). Moisture content in cheese with CRC having the highest value (73.3%) and MSE cheese the least (55.8%). Total solids and protein values (44.2 and 23.4% respectively) were higher in MSE cheese than others while the lactose and fat (0.523 and 15.1% respectively) were also higher in PWE cheese. Vitamins A and C contents (178 and 0.142mg/100g respectively) were higher in SAE cheese than others while the mineral concentrations (Na, Ca, P and Mg) varied among the different cheeses. Acceptability scores were 4.13, 4.13, 4.00, and 3.63 for SAE, SSE, PWE and MSE respectively. There was no difference in acceptability for MSE and CRC. In comparison with cheese purchased from Fulani women, Sodom apple, pawpaw and soursop precipitated cheese had better consumer acceptance than CRC (acceptability score of 3.63). It may therefore be concluded that all coagulants used have potentials for replacing Sodom apple in cheese production in Nigeria.

Key words: Calotropis procera, moringa, sodom apple, soursop, unripe pawpaw, wara

Introduction

Milk is a common food source in the human diet that is directly available for consumption (Belewu 2006). It is secreted by female mammals for the purpose of feeding their offspring as it contains essential nutrients for promoting good health and survival of their young ones (Ibhaze et al 2014). Cheese production helps in preservation of essential nutrients in milk. Cheese is a fresh or ripened product obtained after coagulation and whey separation of milk, cream or partly skimmed milk, butter milk or a mixture of these products (James 2013).

The best known coagulant used by cheese-makers for many varieties of cheese is rennet. (Badmos and Joseph 2012). Rennet is obtained from the fourth stomach (abomasum) of the young calf. In Nigeria, Sodom apple leaf extract (known as ewe bomubomu among Yorubas) is commonly used as coagulant for cheese making. This leaf contains an organic acid called c alotropain which has the ability to solidify or coagulate milk (Akinloye and Adewumi 2014). Coagulation could be achieved by increase in the acidity, extended heating or enzyme activity (Adepoju et al 2012). Pawpaw contains a proteolytic enzyme (papain) which has the ability to coagulate milk (El Moussaoui et al 2001), soursop pulp and Moringa oleifera seed are acidic and can increase the acidity of milk resulting in clotting of milk (McGorrin, 2007; Amna et al 2014). However, despite the fact that Sodom apple is very useful in cheese making industry in Nigeria, it has not been cultivated for commercial use (Adetunji and Salawu 2008). Hence, there is need to evaluate other cheap and available coagulants for cheese production and the nutritional quality of the cheese produced.

Materials and Methods

Fresh whole cow milk was obtained by hand milking from lactating White Fulani cows at Ipinsa cattle ranch in Akure, Ondo State, Nigeria. Soursop and pawpaw fruits were sourced from an open market in Akure while Sodom apple leaves and Moringa seed were obtained from a backyard farm in Ijakpo estate within Akure, Ondo state.

Preparation of Juice Extracts

Fresh Sodom apple leaves were weighed and crushed using a mortar and pestle. The crushed leaves were soaked in distilled water at ratio 1:1 (w/v). After 10 minutes, the mixture was sieved using a muslin cloth to collect the extract. Washed medium sized soursop fruits were peeled to obtain the pulp, mixed with distilled water at ratio 1:1 (w/v) using a juice blender and filtered into a labeled bottle. Same procedure was observed to obtain extract from unripe pawpaw fruits. Moringa seed coats were removed to obtain the clean kernels and 500 g was soaked in 1 litre of distilled water for 12 hours after which it was blended and then filtered.

Preparation of Cheese

Raw milk was divided into four parts of 1000 ml each. The milk was heated to a temperature of 50°C inside a metal pot placed on a low - intensity burner (regulated stove). The extract (100 ml) of each coagulant was added and heating of the milk continued with intermittent stirring until boiling and coagulation was achieved. The curds formed were poured into a sieve of 0.2mm to drain the whey. Draining of the whey lasted for 45 minutes by placing a weight of 2.5 kg on it for proper drainage. The experiment was replicated thrice.

Chemical composition and Sensory Evaluation

The chemical composition of the raw milk and cheese samples produced with the different coagulants and that of the commercially retailed cheese were carried out according to AOAC (2009) for moisture content, total solid, protein, fat and ash. Lactose was analysed using the method of Kirk and Sawyer (1991). The mineral composition of the cheese samples (calcium, phosphorus, magnesium and sodium) were determined using Atomic absorption spectrophotometer as described in AOAC (2009). Also, the vitamins A and C composition of the cheese was carried out according to the methods of Rutkowski and Grzegorczyk (2007).

The sensory characteristics of the cheese samples were judged by 16 semi-trained panelists drawn from students and staff of the Department of Animal Production and Health, Federal University of Technology, Akure for colour, aroma, texture, taste, and over all acceptability using a five-point hedonic scale ranging from 5 (highest score) to 1 (lowest score).

Experimental design and Statistical Analysis

The completely randomised design was adopted. Data obtained were subjected to one-way analysis of variance and significant means were separated using Duncan’s multiple range F- test using the SAS (2008) version 9.2.

Results and Discussion

The proximate composition of the milk used in the production of cheese is shown in Table 1.

The moisture content of the milk was 89.5%, total solids 10.5%, protein 3.58%, fat 4.55%, ash 0.832% and lactose 3.53% while the pH was 6.50. The 4.55% of fat observed was within the range of 3.78-5.71% butter fat reported by Ndubueze et al (2006) in the milk of grazing White Fulani cows fed poultry waste-cassava peel based diets but higher than the fat content (4.10%) reported by Olorunnisomo and Ibhaze (2010) in fresh milk collected from a White Fulani herd. The 3.58% milk protein and 10.5% total solids were slightly lower than the range of 3.7- 3.8% milk protein and 13. 57% total solids for the milk of grazing White Fulani cows reported by Olafadehan and Adewumi (2010). The ash (0.832%) which represents the mineral content obtained in this study fell within the range 0.82 to 0.99% obtained by Ndubueze et al (2006). The differences in the proximate composition of the milk from the cows could be attributed to climatic conditions, seasonal variations, feed resources and general management of the cows (O ̓ Connor 1995). The chemical composition of soft cheese produced using different locally sourced coagulants and commercially retailed cheese is presented in Table 2. The moisture content in cheese produced using different coagulants varied from 55.8 – 61.6%; protein;18.6– 23.4%; fat; 12.0 -15.1%; ash; 0.48 – 1.80%; and lactose; 0.37 – 0.52%.

The moisture content of cheese coagulated with pawpaw fruit extract (PWE) was higher than that from sodom apple extract (SAE). This agrees with the report of Adetunji and Salawu (2008), that the moisture content of cheese precipitated with Carica papaya (pawpaw) leaves was higher than that precipitated with Calotropis procera (Sodom apple) leaves. Values obtained in this study were lower than 70.75% reported by Alalade and Adeneye (2006) except for the CRC. These differences may be attributed to different processing methods adopted by the researchers, variations in the quality of coagulants used and the coagulating strength of the plants used. Also, the differences in the moisture content of the commercially retailed cheese and cheese precipitated with SAE could be the effect of the weight placed on the SAE cheese prepared in this study which ensured that more whey was expelled from the cheeses than the control which normally is not weighted. It must be noted however that higher moisture content is not preferred because it could favour the growth and proliferation of microorganisms, thus reduces the shelf- life of cheese (Adegoke et al 1992). The commercially retailed cheese (control) had the highest moisture content and lowest total solids while cheese made using Moringa seed extract (MSE) had the lowest value of moisture content but highest total solid content. This could be attributed to the coagulating strength of the extract. Also, the total solids in cheese depend on the ability of the coagulants to precipitate the protein and fat in the milk (Ebing and Rutgers 2006). The protein content (23.4%) of cheese made using MSE was higher than values of other coagulants, suggesting that the enzyme in Moringa seed extract incorporated more whey proteins in the cheese mass (Mahami et al 2012). The fat content obtained in this study was higher than the values obtained by Olorunnisomo and Ikpinyang (2012). This may be due to the ability of MSE to incorporate more milk fat into the cheese body than other coagulants. The ash contents of cheese made from different coagulants and the CRC (control) ranged from 0.482- 1.80%.

The sensory and organoleptic properties of cheese produced using different locally sourced coagulants and the commercially retailed cheese is presented in Table 3. In terms of colour, cheese made with PWE had a higher score than others while cheese made with SAE had the least score (1.88). The aroma of cheese coagulated with SAE (4.50) was higher (p<0.05) than others while that of CRC (3.38) had the least value. Cheese coagulated with MSE and the CRC showed least (3.63) acceptability when compared with others. Cheese from SAE and SSE had higher acceptability of 4.13. Moringa seed processed cheese was least preferred in terms of taste, texture and colour which suggests that consumers were not used to consuming cheese precipitated with moringa seed (Olorunnisomo and Ikpinyang, 2012). Also, the sweet taste of cheese made from SSE and PWE could have influenced its preference over MSE cheese. However, there was no difference (p>0.05) in the overall acceptability.

Vitamin and mineral composition of cheese made using different coagulants and CRC is shown in Table 4. The vitamin A content of cheese made from SAE (178mg/100g) was higher (p<0.05) than cheese made from MSE (167mg/100g), PWE (124mg/100g), SSE (42.3mg/100g) and CRC (158mg/100g). The highest vitamin C content was observed in cheese made from SAE (0.14mg/100g) followed by the CRC (0.11mg/100g) and the least values were obtained in PWE, MSE and SSE which were not different (p>0.05). Vitamin A content in cheese coagulated with Sodom apple (Calotropis procera) leaf extract was highest followed by that of the Moringa seed extract. It has been reported that Moringa seed is rich in vitamins A and C (Moringa Facts 2015). Onyechi et al (2012) reported that soursop pulp has vitamin A content of 192.5 IU (57.75mg/100g) which is lower than that of the unripe pawpaw pulp 1354.9 IU (406.61mg/100g). The low values of vitamin C in cheese samples could be due to the heat labile nature of vitamin C. The higher vitamin C content in SAE cheese may have been influenced by the shorter coagulation time which did not affect the vitamin, compared to the longer coagulation time and lower vitamin C content observed in other cheeses. The similar values of sodium obtained in the SAE and CRC cheeses could be as a result of the same coagulant used. Calcium content was higher (p<0.05) in cheese made from SSE (4.29g/kg) and PWE (4.26g/kg) and lowest in CRC (1.17g/kg). Phosphorus content in cheese made from PWE (3.32g/kg), MSE (3.15g/kg) and SSE (2.49g/kg) were lower than values obtained in cheese made from SAE (5.32g/kg) and CRC (3.44g/kg) while magnesium concentration was not different (p>0.05) in all the cheeses. The higher sodium and calcium contents in SSE cheese in this study is a reflection of the higher contents of these minerals in fresh soursop pulp. However, the results obtained in this study for mineral concentration in the different cheeses were lower compared to those obtained for cheese made using steep water alum, Calotropis procera and calcium chloride (Omotosho et al 2011).

Conclusion

• Among the plant extracts explored, unripe pawpaw and soursop cheeses were most preferred. They had qualities that compare favourably with Sodom apple and can be used when access to Sodom apple becomes limited.

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Received 21 July 2017; Accepted 28 September 2017; Published 2 November 2017

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