Hybrid paneer (cottage cheese) : influence of mung bean protein isolate on the texture, microstructure, and gastro-small intestinal digestion in vitro of paneer : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Food Technology, Massey University, Palmerston North, New Zealand
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2021
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Massey University
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Abstract
The global population is estimated to grow to about 9.6 billion by 2050 thus raising the demand for animal-based protein. Due to the huge rise in population, there is a rising concern among the industries as well as government agencies regarding feeding the growing population. Partially replacing milk proteins with plant protein isolate is an interesting opportunity to develop novel food products with unique functionalities along with reducing the demand for animal proteins. Mung bean protein due to its high protein content, health benefits, and good functional properties can be utilised as a potential source of high-quality protein ingredients. The effect of partially replacing cow milk with mung bean protein isolate (MBPI) on the texture, microstructure and digestibility of paneer (acid-heat coagulated cheese) was investigated in this study in order to identify the potential of MBPI to partially replace milk proteins. Cow milk-mung bean paneer (CMMBP) was successfully developed by replacing 30 % of the milk with MBPI by keeping the overall protein content similar to cow milk. The developed CMMBP had higher protein and moisture content when compared to cow milk paneer (CMP) and was shown to have lower fat content. Colour analysis showed a slightly darker colour in CMMBP with the incorporation of MBPI. Small amplitude oscillatory tests showed higher storage modulus (G′) values than loss modulus (G″) values throughout the frequency range and showed a higher G′ value in CMMBP compared to CMP, indicating greater elastic properties. Loss tangent (Tan δ) values of both the paneer samples were always less than one indicating a dominant solid-like nature. Texture profile analysis of the samples showed a significant reduction in the textural properties like hardness, cohesiveness, chewiness, and springiness values in CMMBP (P<0.05). This may be due to the presence of globular mung bean proteins entrapped within the milk protein network thus preventing the formation of a compact protein network resulting in lower textural attributes. This is supported by the confocal microscopy results that showed protein aggregates of varying sizes within the casein matrix in CMMBP in contrast to a much uniform structure in CMP. In vitro gastro small intestinal digestion of the paneer samples was also performed according to INFOGEST protocol to evaluate its protein digestibility under stimulated gastric phase for 1 hour and stimulated small intestinal phase for 2 hr. The digests were analysed using SDS-PAGE and ninhydrin assay for determining the protein hydrolysis and free amino N values during digestion. Ninhydrin results showed a lower release of free amino N in the gastric phase compared to the small intestinal phase in both samples. The free amino N release in CMMBP was significantly lower than CMP during the small intestinal phase (P<0.05). This can be further confirmed by the results of SDS-PAGE which showed the presence of resistant peptides during the intestinal phase in CMMBP, depicting a lower rate of protein digestion. This can be explained due to the presence of anti-nutritional factors, the structural arrangement of proteins and complex formation due to the interaction of proteins with other seed components present in MBPI. Further studies on the addition of calcium chloride and hydrocolloids like carboxymethyl cellulose and pre-gelatinised starch need to be done in relation to the improvement of textural and sensory properties of paneer. The effect of various processing techniques on the digestibility of plant protein added to the protein formulation also needs to be studied.
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