Technology of protein isolate pumpkin seed meal and food products using it

Abstract

The dissertation is devoted to experimental research and its scientific confirmation, regarding the substantiation of the technology of obtaining protein isolate from pumpkin seed meal with increased protein content and high functional and technological properties using the method of alkaline extraction, the action of ultrasound, isoelectric precipitation and pH-adjusting treatment. It has been experimentally confirmed that the use of the developed protein isolate from pumpkin seed meal in the technology of meat sausages and biscuits makes it possible to increase their biological value while fully preserving the high structural-mechanical and organoleptic characteristics of these products. In the first chapter, the existing problem of accumulation of oilseed meal waste, namely pumpkin seed meal, which contains a large amount of complete protein, and its irrational use is considered. Known methods of obtaining protein isolates from oilseed meals are summarized, their advantages and disadvantages are described. The functional properties of protein isolate, necessary for use in the food industry, are analyzed, and the product technologies in which protein isolates are most often used and for what purpose are described. In the second chapter, the general plan of scientific research is formulated, the main direction of the dissertation work is reflected, and research materials and methods are presented. All experimental methods and equipment are described in this section. Standard and generally accepted research methods were used to study functional properties, structural properties, sensory parameters, consistency, physicochemical and microbiological analyses. Scientific mathematical and statistical methods of processing experimental results are described. The research was carried out at Hezhou University in China, Sumy National Agricultural University in Ukraine, the results of experiments are confirmed by relevant research protocols. The third part compared the functional characteristics of four different oilseed protein isolates: peanut protein isolate, pumpkin seed meal protein isolate, sunflower seed meal protein isolate, and soy protein isolate. The results showed that different protein isolates had different functional characteristics. The foaming capacity of peanut protein isolate showed the highest value of 18.18% compared to pumpkin seed meal protein isolate (3.88%), soybean protein isolate (7.76%) and sunflower seed meal protein isolate (9.33%). The maximum value of the emulsifying ability was demonstrated by the soy protein isolate, which was 100.84 m2/g. The soaking time of 11.02 s and the fat absorption capacity of 1.34 ml/g of pumpkin seed meal protein isolate had the best indicators compared to other types of protein isolates. This makes it possible to consider the protein isolate from pumpkin seed meal as a potential additive to meat products and can improve the fat absorption properties, which in turn have the greatest impact on the taste qualities of meat products. In addition, pumpkin seed meal protein isolate does not affect the organoleptic and nutritional value of food products, as it does not contain chlorogenic acid, such as sunflower seed meal protein isolate. The method of ultrasonic alkaline extraction and acid precipitation has been developed. To do this, a three-factor, three-level Box-Behnken design, response surface methodology was used to optimize protein isolate conditions such as sonication power, sonication time, and liquid-to-solid ratio. Appropriate statistical methods and polynomial-regression analysis of experimental data were used, which made it possible to obtain a quadratic polynomial equation. Response surfaces were used to demonstrate the effects of the interaction of independent factors on the yield of protein isolate extraction from pumpkin seed meal. In addition, it was found that the best conditions for the extraction of protein isolate from pumpkin seed meal were at an ultrasound power of 456 W, an ultrasound period of 22 min, and a liquid-to-solid ratio of 27 ml/g. These values were obtained by solving the regression equation and examining contour plots of the response surface. The results showed that the experimental value of protein isolate yield from pumpkin seed meal (80.76 g/100 g) was quite similar to the predicted value (81.86 g/100 g). This indicates a strong agreement between the experimental value and the predicted value of the regression model. However, it will be impossible to achieve such results in industrial production, since the protein content in the meal fluctuates to a large extent and the predicted yield of protein isolate from the pumpkin meal will fluctuate within 50%-60%. Therefore, it was confirmed that the extraction conditions of protein isolate from pumpkin seed meal can be accurately predicted using the response surface equation. The possibility of using ultrasonic alkaline extraction to obtain protein isolate from pumpkin seed meal was revealed. However, this method does not significantly affect the functional properties of the protein isolate from pumpkin seed meal, and preference was given to the method of pH- shifting treatment. Pumpkin seed meal protein isolate was subjected to a pH-adjusting treatment to improve its functional characteristics. Pumpkin seed meal protein isolate was tested at several pH levels (pH 2, pH 4, pH 6, pH 8, pH 10, and pH 12), which were designated as samples PSPI 2, PSPI 4, PSPI 6, PSPI 8, PSPI 10 and PSPI 12, respectively. The effect of pH-adjusting treatment on the solubility of PSPI samples was investigated. An increase in solubility was observed only in sample PSPI 8 (55.5%) compared to the control PSPI (45.6%), while the solubility of samples PSPI 2 (13.7%), PSPI 4 (10.8%), PSPI 10 ( 41.8%) and PSPI 12 (13.4%) decreased. Then the average particle size and zeta-potential of soluble protein were determined in PSPI samples followed by electrophoresis in sodium dodecyl sulfate polyacrylamide gel. After the process of changing the pH, the average particle size of samples PSPI 2, PSPI 4 and PSPI 12 decreased. PSPI 2 and PSPI 12 samples had a low zeta potential. Other samples did not show a significant difference in these two indicators. In addition, an increased amount of soluble protein bands at 33 kDa and 25 kDa was detected in the PSPI 8 sample. The influence of pH-shifting treatment on heat-induced gel characteristics of protein isolate from pumpkin seed meal was studied. In the obtained gels, the water absorption capacity was studied, textural analysis was carried out (hardness, adhesiveness and cohesion), and the state of water was determined. Compared to the control, the water-absorbing capacity of PSPI 6 and PSPI 8 samples was significantly higher. Only the hardness of the sample PSPI 6 showed an increased value when checking the texture of the gels. The cohesiveness of PSPI samples after treatment at pH 2, pH 4, pH 6, pH 8, pH 10, and pH 12 did not change significantly compared to the control. The adhesiveness of samples PSPI 2, PSPI 4 and PSPI 10 decreased significantly, but the adhesiveness of PSPI 6, PSPI 8 and PSPI 12 samples did not change significantly compared to the control. The state of water in gels, after pH- shifting treatment, changed as a result of nuclear magnetic resonance in a low-frequency field. PSPI 4 and PSPI 6 samples had a significantly lower level of bound water compared to the control. However, samples PSPI 8, PSPI 10 and PSPI 12 had a higher level of bound water compared to the control. The immobilized water of sample PSPI 6 had a higher value compared to samples PSPI 2, PSPI 4, PSPI 8, PSPI 10, and PSPI 12. These findings suggest that pH-shifting treatment will be a practical and affordable way to modify the functional properties of protein isolate gels from pumpkin seed meal, offering fundamental insight into future uses of this isolate in food technology. The thermal, structural and emulsifying characteristics of samples of protein isolate from pumpkin seed meal processed by the method of pH- shifting treatment were studied. The PSPI control showed denaturation temperatures of 87.67 and 104.11°C, with corresponding enthalpies of 1.66 and 0.37 J/g, according to differential scanning calorimetry analysis. Only PSPI sample 2 among other PSPI samples did not change significantly compared to the control PSPI, in terms of denaturation temperatures and enthalpies. Emulsion stability in samples PSPI 2, PSPI 4, and PSPI 12 increased by 42.32, 67.58, and 40.87%, respectively, while the emulsifying activity of PSPI 2, PSPI 4, and PSPI 12 samples increased by 205.84, 298.98 and 288.69%, respectively. The content of disulfide bonds in samples PSPI 2, PSPI 4 and PSPI 12 improved (p < 0.05) by 7.46, 9.28 and 5.01%, respectively, while the content of free sulfhydryl groups in them decreased (p < 0.05) by 36.69, 44.39, and 29.11%, respectively, which indicates that the increased emulsifying properties of samples PSPI 2, PSPI 4, and PSPI 12 can be associated with an increase in the content of disulfide bonds and by reducing the content of free sulfhydryl groups. However, the hydrophobicity of the surface and the particle size of the PSPI samples did not correlate in any way with their emulsifying ability. In the fourth section, a one-way test and an orthogonal test were conducted to determine the optimal formulation of cookies with pumpkin seed meal and pumpkin seed meal isolate, in which the ratio of low gluten wheat flour, pumpkin seed meal, pumpkin seed meal isolate and konjac powder was 2:1:1, the amounts of vegetable oil and butter were 4.0% and 12.0%, respectively, and the amount of maltitol was 20.0%. Nutritional analysis shows that pumpkin seed meal and pumpkin seed meal isolate cookies contain 59.2% carbohydrates, including 19.1% dietary fiber, 20.4% protein, 18.0% fat and 1.8% ashes. With the help of orthogonal tests and univariate studies, a new recipe for meat product was created. The ideal production parameters were 1.5 g/100 g of protein isolate from pumpkin seed meal, 80 g/100 g of lean meat. The sensory evaluation of the developed meat product was 8.5 points, which was confirmed by the relevant acts of tasting. The moisture, ash, protein and fat content were 51.16 g/100 g, 2.26 g/100 g, 15.22 g/100 g and 23.15 g/100 g, respectively. This study can provide important information for the further use of pumpkin seed meal protein isolate in the technology of minced meat products such as sausages and meet-containing breads. Degustation of biscuits and meat products with the addition of pumpkin seed meal protein isolate was carried out at Hezhou University in China. Degustation results were recorded in the relevant degustation protocols. In the fifth chapter, the results of the practical application of the technology of protein isolate from pumpkin seed meal are presented and the socio-economic effect of the introduction of this technology into production is investigated, the cost of production is calculated, and data on the popularization of the research results are summarized. The economic feasibility of introducing the developed technologies into the practical activities of food enterprises has been proven.