Abstract
Paneer is an acid coagulated concentrated indigenous Indian dairy product. The texture of paneer manufactured from a developed automatic machine was studied with respect to the processing parameters such as coagulation temperature (70–90°C), pressure (0.3–0.6 MPa), types of coagulant (vinegar and citric acid), and milk (cow, buffalo, and full cream milk). The paneer samples were analysed for texture profile analysis of hardness, adhesiveness, springiness, gumminess, chewiness, and cohesiveness. An inscribed central composite design was used to optimize the desired textural characteristics of paneer such as minimum hardness and maximum springiness of paneer. The optimization result concluded that the full cream milk at the coagulation temperature of 88°C with citric acid at pneumatic pressure of 0.3 MPa would result on minimum hardness of 105.84 N and the springiness value of 0.6073, and the result was validated.
1. Introduction
Paneer is an Indian cottage cheese obtained by heat treating the milk followed by acid coagulation. Paneer is a low-cost animal-based protein rich product with biological value of 80–86 [1]. It is traditionally prepared from buffalo milk and extensively consumed in India as an analogue to meat. Cheese contains high amount of saturated fatty acids which alleged to increase low density lipoprotein that heightens the risk of cardiovascular disease. However, the nutrients present in cheese viz., vitamin K benefits cardiovascular health by reducing vascular calcification [2, 3]. Artisanal cheese has significant cultural and historical potential characterized by employing traditional methods from different regions viz., north, south, northeast, and central Brazil. However, production and consumption data are restricted, and physiochemical, sensory, and textural properties are not examined [4]. Paneer production involves the fractionation of milk into curd (agglomeration of solid mass) and whey (liquid portion). This curd is further pressed into blocks and cooled. The product is produced manually at cottage level and pressed with dead weight in unhygienic way. To alleviate human drudgery and human intervention in the cottage-scale production, a machine mounted with programmable logic control (PLC) was developed by the authors to automate the paneer production [5]. The machine was comprised of double-jacketed milk heating tank, coagulation tank, and pressing unit attached with the pneumatic press. The milk heated to 70–90°C is drawn to the coagulation tank containing vinegar or citric acid and kept for 1 minute for facilitating the complete coagulation process, and the coagulum is discharged through solenoid valve to the pressing unit where whey is separated from curd and the chhana is pressed pneumatically. It is important to study the textural behaviour of the paneer when produced mechanically.
The textural quality of paneer is affected by various factors viz., type of milk, quality of milk, coagulation temperature, coagulant, and pH of coagulant [1, 6],which will have a strong influence on yield, moisture, acidity, and sensory attributes of paneer. There are studies which investigated textural properties of soy paneer from soy milk using different coagulants [7]. Also, the chemical and sensory qualities of paneer were studied on account of coagulation temperature and coagulants [8]. Research work on mechanization revealed the influence of pressure and pressing time on the textural quality of paneer samples [9]. The functional, textural, physicochemical, and sensorial properties of cottage cheese standardized with food grade coagulants were also studied [10]. It was observed that there were limited literature on the textural profile of paneer with respect to coagulation temperature, coagulant, pressure, and type of milk, and dearth of literature is available on how machine parameters affect the textural properties of paneer manufactured from an automatic machine. Hence, the present study investigated the influence of coagulant and machine parameters on the textural quality of paneer on different type of milk [5]. In this context, the objective of the study was to evaluate the effect of machine parameters viz., temperature and pressure in combination with different coagulants on the textural property of paneer through a computerized optimization tool in order to bring out a product of customer interest.
2. Materials and Methods
2.1. Milk
The milk samples were purchased from local market and the fat and SNF (Solid Not Fat) of milk samples were measured using electronic machine (EKOMILK ULTRA PRO—make: Everest instrument Pvt. Ltd, Chennai).
Three different types of milk were used for paneer production viz., cow milk, buffalo milk, and full cream milk. The fat, SNF, and acidity of cow, buffalo, and full cream milk were 3.80 ± 0.20%, 7.50 ± 0.10%, and 0.14 ± 0.02%, 7.15 ± 0.25%, 8.35 ± 0.10%, and 0.17 ± 0.01%, and 6.00 ± 0.10%, 9.00 ± 0.05%, and 0.16 ± 0.01%, respectively. Milk samples were used for paneer preparation in the developed machine.
2.2. Preparation of Paneer
The paneer samples were prepared from the PLC-operated machine designed at the Department of Food Plant Operations, College of Food and Dairy Technology, Tamil Nadu Veterinary and Animal Sciences University, Chennai, India. Paneer samples were prepared from cow milk, buffalo milk, and full cream milk with citric acid and vinegar separately at three different coagulation temperatures of 70, 80, and 90°C. Pressures were varied between 0.3 and 0.6 MPa through pneumatic cylinder. The pressed paneer block was then immersed in cold water for 15 min and stored at −20°C till the conduct of study. Table 1 depicts the treatment conditions with various levels of factors taken.
2.3. Moisture Content
Moisture content of paneer samples were determined as it is one of the important parameters related with the textural behaviour of paneer while varying temperature and pressure during production process. The moisture content of paneer was determined using the hot air oven method [11].
2.4. Textural Properties of Paneer
Textural attributes, namely, hardness, adhesiveness, springiness, cohesiveness, chewiness, and gumminess of paneer samples were analysed using texture analyser (TA.XT2i-Stable Microsystems, UK) available at Tamil Nadu Agricultural University, Trichy, India. The paneer samples stored at −20°C in a deep freezer (make: Voltas, 500 L capacity, India) were brought up to 4°C and cut into uniform cubes of (20 × 20 × 20 mm) dimensions to conduct texture profile analysis. Compression platen (P/75) with 75 mm diameter made up of stainless steel was used to observe the textural properties of paneer. The test conditions viz., load cell capacity, contact force, return speed, and deformation rate were 50 kg, 5 g, 10 mm/s, and 600 mm/min, respectively, were selected in the texture analyser.
2.5. Sensory Evaluation
Paneer samples were cut into uniform blocks and were given to a panel of six trained judges (Four female, two male) from the College of Food and Dairy Technology, Chennai to evaluate the sensory properties of samples. Each panelist is provided with 20 g of paneer at room temperature. The sensory attributes including colour, appearance, body, texture, flavour, and overall acceptability of the product were analysed using 9-point hedonic scale rating [12]. Texture is the most important quality that attracts the consumer, especially in cheese industry [13].
2.6. Statistical Analysis
Each experiment was replicated thrice in the developed machine, and the results were expressed as mean ± SE. The data were further analysed using inscribed central composite design response surface methodology tool in MINITAB 17.0 software to optimize the desired textural characteristics of paneer. The textural properties were provided with weightage factor in accordance with the consumer preference. The cohesiveness and springiness properties of paneer were set to be maximum and other textural properties viz., hardness, adhesiveness, chewiness, and gumminess were set to be minimum. A weightage value of 2 was given to hardness and springiness, and the remaining properties were given the weightage value of 1. The importance of the properties studied was treated equally as shown in Table 2.
2.7. Validation of Optimized Process Parameters
The paneer samples prepared under the optimized conditions (pneumatic pressure, coagulation temperature, and coagulant) was estimated for the textural properties viz., hardness, adhesiveness, gumminess, chewiness, cohesiveness, and springiness for the validation of predicted values. The experimental values were compared with predicted values, and relative error % was determined.
3. Results and Discussion
The effect on texture profile of paneer made from cow milk, buffalo milk, and full cream milk due to coagulation temperature, coagulant, and pressure are discussed. The textural profile includes hardness, cohesiveness, gumminess, springiness, and chewiness.
3.1. Hardness of Paneer
The force applied to deform paneer upto 30% of its original size is termed as hardness [14–16]. It was observed from Table 3 that the vinegar-based cow milk paneer recorded the hardness value of 117.3183 to 144.9238 N at 70°C, when the pneumatic pressures were in the range of 0.3 to 0.6 MPa. Increasing pneumatic pressure resulted in increased hardness values. This is related with the reduction in the moisture content of paneer samples (Table 4) due to increased pressure. The hardness values of buffalo milk and full cream milk were in the range of 148.1248 to 359.4945 N and 112.3383 to 378.4305 N, respectively, whereas the citric acid-based paneer recorded the least value of hardness (100.7030 N) followed by full cream milk and buffalo milk at 70°C at 0.3 MPa. The highest hardness values were 378.4305 N and 389.0119 N for vinegar and citric acid-based full cream milk, respectively, at 0.6 MPa when the coagulation temperature was 70°C. It was because of the temperature of coagulum; the lower temperature, and higher pressure or longer pressing due to which the higher hardness was experienced at lower temperature of coagulation [9]. The vinegar and citric acid-based paneer samples were significantly differed on the hardness values at 1% level at all temperatures and test pressures.
Irrespective of the coagulant, an increasing trend of hardness values among the test pressure levels and milk samples was observed at each coagulation temperature. Since the reduction in moisture content with respect to pressure applied, the hardness was found increased. The result was found in agreement with the results of [17] that the moisture content was in negative correlation with hardness of Sandesh (an Indian traditional chhana-based sweet). On comparison among vinegar-based paneer samples, the highest hardness was 463.1316 N for buffalo milk at 0.6 MPa and lowest was 104.4203 N for cow milk at 0.3 MPa when the coagulation was performed at 90°C whereas the citric acid-based paneer samples recorded the least hardness of 100.7030 N for cow milk at 70°C at 0.3 MPa, and the highest was 537.4431 N for buffalo milk at 90°C at 0.6 MPa. It was evident that higher temperature and pressure resulted in increasing the hardness of paneer irrespective of the coagulant and milk (Figures 1–3). This was due to the phenomenon of “syneresis” which resulted in separation of moisture from curds at elevated temperatures. In addition, the increased pneumatic pressure reduced the moisture content of paneer, thereby the hardness values of paneer were found to be increased [8]. Reference [1818] developed soy paneer and found that hardness was increased with coagulation temperature up to 90°C.
It was observed that the independent variables viz., coagulation temperature, pressure, coagulant, and types of milk had significant effect on the hardness of paneer samples individually and in combination at 1% level except that the combination of pressure and coagulant did not significantly influence the hardness of samples.
3.2. Adhesiveness of Paneer
The vinegar-based cow milk paneer samples had the highest adhesiveness values of −20.27 g·s at 90°C and 0.6 MPa, whereas the least value of −42.53 g·s was observed at 70°C at 0.3 MPa as indicated in Table 5. The increase in pressure resulted in increasing adhesive property irrespective of the temperature and milk. Vinegar-based buffalo milk paneer recorded the highest and lowest values of −24.87 g·s at 90°C at 0.6 MPa and −41.07 g·s at 80°C at 0.3 MPa, respectively. A lowest value (−41.07 g·s) of adhesiveness was found for vinegar-based full cream milk paneer at 90°C at 0.3 MPa and the highest (−17.23 g·s) was found at 80°C at 0.6 MPa. While comparing treatments based on temperature, the treatments significantly differ at 1% level, and also, all the machine parameters, coagulant, and types of milk significantly influence the adhesive property of paneer at 1% level.
The highest value (−16.70 g·s) of adhesiveness was noted at 90°C at 0.6 MPa for citric acid-based cow milk paneer, and the lowest was noted against the sample at 70°C at 0.3 MPa. Full cream milk recorded the highest adhesiveness at 80°C at 0.6 Mpa, whereas the lowest was against the sample at 90°C at 0.3 MPa. The citric acid-based buffalo milk paneer samples were highly adhesive (−20.50 g·s) at 90°C at 0.6 MPa and least adhesive (−40.70 g·s) at 70°C at 0.3 MPa. It was observed interestingly that the adhesiveness increased with increasing coagulation temperature and pressure irrespective of the milk samples and coagulant. The result was found on par with the results of [18, 19] who advocated the increase in adhesive property of dehydrated paneer after rehydration process when the temperature was increased.
[1717] results are comparable that adhesiveness was negatively correlated with moisture content and positively correlated with fat content of milk (). The highest value of adhesiveness was found on par for citric acid-based cow milk paneer (80 and 90°C at 0.6 MPa) and full cream milk paneer (80°C at 0.6 MPa).
3.3. Springiness of Paneer
Elasticity is denoted as springiness [10]. It was observed from Table 6 that the cow milk paneer prepared from vinegar recorded the highest springiness value of 0.654 at 80°C at 0.3 MPa and lowest value of 0.450 was found at 90°C at 0.6 MPa. The value of springiness found decreased when pressure increased from 0.3 MPa to 0.6 MPa at 80°C and 90°C, whereas vinegar-based buffalo milk paneer samples recorded decreasing trend when increased pressure at 70°C and 80°C. The range of springiness for buffalo milk paneer found from 0.585 to 0.714, and the full cream milk paneer ranged from 0.457 to 0.656. The full cream milk confirmed the rising and falling trend at all test pressures and temperatures.
A decreasing trend of springiness values of citric acid-based buffalo milk paneer was observed at all temperatures and pressure levels as shown in Figure 4, and cow milk paneer samples found decreasing when the pressure levels increased at 80°C and 90°C. The decreasing springiness with increased temperature was found on the results of [19]. The least springiness value of 0.398 recorded for citric acid-based cow milk paneer at 0.6 MPa at 90°C and the highest value of 0.758 was found for citric acid-based buffalo milk paneer at 70°C for 0.3 MPa. Full cream milk paneer was observed with increasing and decreasing trend of springiness at increased pressure levels against each coagulation temperature. The same was confirmed by [1818] that reported that springiness of soy paneer was found increased up to 85°C and remained constant up to 90°C and decreased with further increase in temperature.
It was observed that the independent variables had significant effect on the springiness of paneer samples at 1% level. The individual interaction of temperature, coagulant, and pressure with the types of milk had significance on the springiness at 1% level.
Hardness and springiness values were higher in buffalo milk paneer than cow milk paneer and full cream milk paneer irrespective of temperature, pressure, and coagulant used. Moisture content of paneer influences the springiness negatively and fat contents positively influence () the springiness of paneer [17]. Comparing the proximate of milk samples, buffalo milk was higher in the fat content (7.15 ± 0.25%) than cow and full cream milk and recorded least moisture contents (Table 3). The same was supported by the results of [20] who compared cow milk paneer and buffalo milk paneer in terms of textural properties.
3.4. Cohesiveness of Paneer
The ratio of area of two compressions in between force and time is designated as cohesiveness [10]. Of the milks tested, vinegar-based cow milk recorded the least cohesive value of 0.364 at 80°C for 0.6 MPa and buffalo milk was found with highest value of 0.527 at 80°C for 0.4 MPa. It was observed from Table 7 that vinegar-based cow milk paneer resulted in reduction of cohesiveness when temperature and pressure increased. A decreasing trend of cohesiveness was observed for full cream milk at 70°C when the pressure increased from 0.3 MPa to 0.6 MPa. The decreasing trend of cohesive property with increasing temperature and pressure was found on par with the results obtained by [1919] and substantiated that the moisture loss and change in proteins might significantly be influenced the textural characteristics.
Citric acid-based cow milk paneer exhibited a decrease in cohesive property against the increase in pressure at 80 and 90°C, whereas the full cream milk exhibited the same trend at 70 and 80°C. Among the citric acid-based paneer samples prepared from the three milk source, buffalo milk showed a highest and lowest values of cohesiveness 0.567 at 80°C at 0.3 MPa and 0.346 at 70°C at 0.6 MPa, respectively. There is an inverse relationship between fat and cohesiveness of cheese as the buffalo milk responded for the least value of cohesiveness [21].
3.5. Gumminess of Paneer
The product of both hardness and cohesiveness is called as gumminess [10]. The gumminess of vinegar-based paneer ranged from 4275.55 (for cow milk at 90°C at 0.3 MPa) to 19636.82 at 90°C for 0.6 MPa. The gumminess values were found increased in commensuration with temperature and pressure as shown in Table 8. The similar trend was also observed for citric acid-based paneer among each milk samples. The cow milk sample recorded the least value (4351.33) of gumminess at 80°C at 0.3 MPa, and buffalo milk recorded the highest value of (21730.62) gumminess at 90°C at 0.6 MPa. Since gumminess is the product of hardness and cohesiveness, similar increasing trend on gumminess with respect to increased pressure and temperature was cumulatively affected [22, 23].
3.6. Chewiness of Paneer
Addition of both gumminess and springiness is called as chewiness. The vinegar-based full cream milk paneer recorded the minimum chewiness value of 2432.27 at 70°C at 0.3 MPa and buffalo milk paneer recorded the maximum value of 13262.20 at 90°C for 0.6 MPa. It was noted from Table 9 that an increasing trend of chewiness was witnessed when pressure and temperature combinations were increased for buffalo milk and full cream milk irrespective of the coagulant used. The vinegar-based cow milk paneer exhibited higher chewiness in lower temperatures, whereas higher chewiness was witnessed at higher temperatures for citric acid-based cow milk paneer. The highest chewiness (11872.29) was observed for citric acid-based paneer at 90°C at 0.6 MPa and the lowest (2374.29) was observed for full cream milk paneer at 70°C at 0.3 MPa. This is due to the higher fat content in the full cream milk, as fat content also have a huge impact on chewiness. Full fat cheese has low values of chewiness as compared to low fat cheeses or cheeses made from skim milk [2121], since the highest was noted against vinegar-based buffalo milk paneer on comparison with citric acid-based paneer samples.
3.7. Sensory Evaluation of Paneer
Figures 5–10 reveal the sensory profile of paneer prepared from cow, buffalo, and full cream milk under various treatment conditions. It was recorded that irrespective of milk used, highly significant () differences were found in values of colour, appearance, body, texture, flavour, and overall acceptability among the samples coagulated with citric acid and vinegar at 70, 80, and 90°C by applying various pressures (0.3, 0.4, 0.5, and 0.6 MPa). Sensory scores were influenced by coagulant used, temperature, and pressure values. Colour and appearance were most significant parameters in case of paneer from consumers’ standpoint. Regardless of milk used, paneer prepared using vinegar as a coagulant scored highest value in colour and appearance. This might be due to the bright colour of the paneer made from vinegar, whereas citric acid exhibited the yellowish white colour on the surface of paneer [12]. Body and texture values of paneer found increased with pressure, thereby hardness values were also found to be increasing with increasing levels of pressure. This might be because increasing pressure values made the paneer firmer [24].
All the independent variables control the overall acceptability values of paneer. Milk fat significantly affects the organoleptic quality of paneer [25]. Thus, buffalo milk recorded the highest overall acceptability (8.13) score when vinegar was used as a coagulant at 80°C at the pressure level of 0.5 MPa.
3.8. Optimization of Process Conditions
Inscribed central composite design adopted from response surface methodology rendered an optimized textural property of paneer with minimum hardness, chewiness, gumminess, adhesiveness, maximum cohesiveness, and springiness depending on the pressure applied, coagulation temperature, and coagulant for the types of milk used in this study. The optimized parameters for the production of paneer with minimum hardness and maximum springiness are given in Table 10. Hence, optimum values of temperature, pressure, and coagulant for cow, buffalo, and full cream milk were 72.2°C, 0.3 MPa, and vinegar, 70°C, 0.3 MPa, and vinegar, and 87.9°C, 0.3 MPa, and citric acid, respectively. Corresponding predicted values of responses were also presented in Table 10. Paneer samples from three different milk sources were prepared with predicted temperature, pressure, and coagulant and experimented for its textural similarities with the predicted properties. The relative error was less than 10% for all the cases proving the model was highly suitable and the values thus obtained were optimized.
4. Conclusion
The process parameters such as coagulation temperature, pressure, type of coagulant, and milk play a major role on the textural properties of paneer. It was understood that minimum pressure (0.3 MPa) with appropriate coagulant and temperature would yield a preferable texture of paneer. The citric acid-based full cream milk had an optimized temperature of 88°C at 0.3 MPa to yield a very soft paneer (105.84 N). The natural coagulants would may be studied in the future along with optimized machine parameters to understand the textural behaviour of paneer.
Data Availability
The data that support the findings of this study are available on request from the corresponding authors. The data are not publicly available due to privacy or ethical restrictions.
Conflicts of Interest
The authors declare that they have no conflicts of interest.
Authors’ Contributions
S. Sivaranjani was responsible for conceptualization; data curation; investigation; methodology; and writing of the original draft. N. Karpoora Sundara Pandian performed conceptualization; funding acquisition; investigation; methodology; project administration; supervision; validation; visualization; and review and editing. S. Parveen was responsible for provision of resources; supervision; and review and editing. D. Baskaran was carried out by conceptualization and provision of resources. V. Arunprasath performed review and editing. V. Eyarkai Nambi performed data curation. R. Pandiselvam was responsible for provision of resources and software and review and editing.
Acknowledgments
The authors expressed deep sense of gratitude to TNAU, Trichy, India, toward permission to use its laboratory for this study and Tamil Nadu Veterinary and Animal Sciences University, Chennai, for its partial financial support.