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Vacuum impregnation of sugar syrup into sub-baric fried Gulabjamun was evaluated as a technological approach to prepare a product of most acceptable quality. Sugar syrup concentrations (40, 50 and 60 °Brix) in combination with process time (2, 4 and 6 min) were analyzed for their effect on product quality in terms of its overall acceptability, expansion ratio, hardness, juiciness and sugar content. The effect of the process conditions on the five listed responses during the vacuum impregnation process was evaluated using response surface methodology and modelled using a second order polynomial equation. The optimum combination was obtained as soaking in a syrup of 55 °Brix for 5 min and was experimentally validated for its real time adequacy. The experimental values of the quality parameters thus obtained were found to be in close agreement with the predicted values.

An attempt was made to develop mathematical models to describe the sorption behaviour and determine the thermodynamic properties of sorption of dry-crystallized Palada payasam mix at different water activities (between 0.113 and 0.973) and temperature ranging from 25 to 35 °C. Samples were prepared using both manual and mechanical mixing during the crystallization process and the equilibrium moisture content (EMC) was recorded using the isopiestic technique to compare the sorption behaviour of both samples. The sorption isotherms were found to follow a J-shape—type III plot, with the sorption capacity decreasing with temperature. The isotherms also exhibited a typical temperature inversion of EMC at water activity > 0.70. The sorption data obtained was fitted to 12 mathematical models for sorption and the Guggenheim, Anderson and de Boer (GAB), Peleg and Iglesias and Chirife models were found to describe the data over the entire range of water activity with a good fit. The isosteric heat of sorption and spreading pressure were determined as a function of moisture content. Isosteric heat of the samples was computed and found to decrease from 51.75 to 47.16 kJ/mol for control (manually stirred) and 49.38 to 47.58 kJ/mol for experimental sample (mechanically stirred) for a range of moisture content up to 29% (d.b). The spreading pressures increased with increasing water activity but decreased with increasing temperature. No significant difference was observed between the sorption properties of the dry crystallized samples prepared using manually and mechanically stirring.

The present work was undertaken to investigate the feasibility of pre-treatment of raw milk with Pulse Electric Field (PEF) treatment before its entry into the processing chain. A custom-designed and fabricated PEF applicator was used for the non-thermal treatment protocol. Raw milk was treated under three treatment protocols, viz., conventionally heat treatment (CHT), PEF treated milk subjected to conventional heat treatment (PT-CHT) and PEF treatment (PT). For the PT protocol, milk was subjected to high voltage (55 kV) square wave of pulse width 900 µs, for 100 s at a frequency of 90 Hz. The treated milk was then converted to two popular products, namely and paneer and khoa, which were evaluated for its physico-chemical, microbiological, sensory quality and shelf stability. Since khoa is a heat desiccated product, it was evaluated only against PT-CHT and CHT treatments. It was observed that PT treatment resulted in paneer with softer body with higher whiteness index, compared to other experimental samples. The PT treatment did not affect the product acceptability and the product had a shelf stability of 12 days under refrigeration, as against 16 days for CHT and PT-CHT treatment. The treatment protocols for milk did not significantly affect the quality and shelf life of khoa. Thus, there is wide future scope to used pulsed electric fields treatment synergistically with conventional heat treatment for inactivation of microorganisms, with better retention of nutritional and physical properties of product which has potential to save considerable amount of energy and time during processing of product.

Recombined milk (RM) can be prepared by blending of butteroil, skim milk powder and water and used for variety of purposes in dairy industry. The present work was undertaken to investigate the feasibility of a custom designed and fabricated universal disperser unit for the preparation of recombined milk. Water, SMP and butteroil were used to manufacture the recombined milk. Three levels of fat viz 1.5%, 3.0% and 4.5% were evaluated to study the effect of fat content on the recombination efficiency of the universal disperser using a high shear saw tooth impeller to impart the required shear and disperse the fat in water–SMP matrix to form a stable emulsion. Two independent parameters i.e. temperature at three different levels (20, 35 and 50 °C) and impeller speed (10,000, 15,000 and 20,000 rpm) were selected for the study. All operations were carried out in heating cum process vessel having working capacity of 3 L. The efficiency of the operation was judged based on the dependent parameters namely, mixing time, mixing index, creaming index, power consumption and overall acceptability. Experiments were designed as per RSM in Design Expert V.10.0 software and results obtained were optimized and predicted solutions were compared with observed data. From the study, the optimal combinations for preparation of recombined milk were obtained as 1.5% Fat RM (17,820 rpm, 48 °C), 3.0% Fat RM (15,701 rpm, 48 °C) and 4.5% Fat RM (15,459 rpm, 48 °C).

An attempt was made to design, fabricate and evaluate a heat exchanger for controlling the matting temperature of Paneer during pressing. Based on preliminary investigations, the range of process parameters to be evaluated during the pressing of Paneer was selected as: pressure (2, 3, and 4 kg/cm(2)), matting temperature (63, 66 and 69 °C) for pressing time of 8, 10 and 12 min. Experiments were designed in a central composite design for 20 runs and the Paneer was evaluated for its moisture content, hardness, springiness, chewiness, cohesiveness, bulk density, porosity and sensory attributes. It was observed that with increasing pressure and matting temperature, the hardness of the product increased; this corresponded with reduced moisture content and porosity of the product. The springiness of the samples correlated linearly with increasing matting temperature and pressing time. Increasing the pressure during pressing resulted in poorer sensory scores. The process conditions for pressing of Paneer under controlled matting conditions were optimised using Response Surface Methodology for moisture content, overall acceptability, hardness and springiness of the pressed product. It was observed that the moisture content of Paneer pressed under controlled matting temperature was marginally lower than the control Paneer, the overall acceptability for the experimental samples was higher with superior body and texture scores.

Nonthermal processes have emerged as alternate techniques of processing as means to ensure microbial safety and preserve the organoleptic and nutritive quality of foods with minimal or negligible exposure to heat. In addition to preservation and enhanced processing effectiveness, these technologies have also been extended to other applications in dairy products, such as, tailored functionality, preservation of bioactive components, and development of hypoallergenic products. Several nonthermal techniques have evolved in recent times, including high-pressure, high-voltage discharge, ultrasound including thermosonication and manosonication, pulsed light, ozone treatment, etc., and its application on dairy beverages have been encouraging. The chapter discusses the basics of and systems employed for these emerging technologies with reference to its application in dairy beverages including, milk and milk-based beverages, fermented dairy drinks, whey, and colostrum. The effect of the aforementioned treatments on the quality and safety (sensory attributes, physicochemical effects, and microbial effects) of the above products will also be reviewed in the chapter.

Processing conditions were standardized for a carbonated sweetened fermented dairy beverage. The optimum level of carbonation for the beverage filled in 200 ml glass bottles was found to be at 50 psi pressure for 30 seconds. The beverage samples were stored under refrigerated conditions (7 °C) and evaluated at weekly intervals for their sensory, chemical and microbial quality. The uncarbonated control samples were found to keep well till 5 weeks of storage while the carbonated beverage was acceptable up to 12 weeks of storage. Carbonation did not significantly alter the pH of the beverage, while a marginal increase in titratable acidity was recorded for the carbonated samples. Carbonation was found to arrest the development of lipolysis and proteolysis in the beverage during storage. Microbiological investigations established the inhibition of yeast and mold growth due to dissolved CO2.

Sorption data were determined by static gravimetric method for cheese–puri mix at 25, 35 and 45C. The Guggenheim-Anderson-deBoer (GAB), Caurie, Henderson, Oswin and Smith isotherm models were attempted to describe the experimental data and were found to describe the sorption behavior of the product adequately. The solid surface area of the product was computed based on the GAB model monolayer moisture contents of the product and was found to increase with temperature. Thermodynamic properties of the product, including the isosteric heat of sorption, sorption entropy, spreading pressure, net integral enthalpy and entropy, were determined as a function of the product moisture content. Application of the enthalpy–entropy compensation theory to the sorption data revealed that the process was enthalpy-driven. The net integral enthalpy and entropy were found to decrease with increasing moisture content and were described as a function of the equilibrium moisture content using a power model. Practical Applications Sorption isotherms are important tools for food scientists to understand the behavior of a food product, especially low-moisture foods, toward the moist air that envelopes its surroundings. They are particularly useful to predict the physical, chemical and microbial stability of the product during storage and reconstitution. Thermodynamic properties of the product provide an insight into the energy requirement associated with moisture sorption and the temperature dependence of water activity. Cheese–puri mix is a value-added convenience dairy product, and information on its sorption characteristics would be useful to monitor its quality and shelf stability.

Precooling is an important postharvest unit operation for tropical fruits like mangoes because of its short postharvest life. Even though it is desirable that the precooling process be as fast as possible, the cooling should not result in any chilling injury to the fruits. Liquid nitrogen (LN2) is a cooling medium with ample potential for use in precooling operations because of its high cooling capacity and inertness of the vaporized nitrogen gas; however, its severe cold temperatures raise concerns on the possibility of chilling injury to the fruits. Hence, the present study was undertaken to compare a system where LN2 was employed in combination with mechanical refrigeration system as the cooling medium, in comparison to common precooling techniques for mangoes (cv. Amrapali) like hydrocooling and air cooling. The precooling performances were compared for the cooling rate, and cooling coefficient and fruit quality were assessed in terms of fruit firmness, color and chilling injury indices. The pH, total soluble solids and titratable acidity of the ripened fruits subjected to the different precooling techniques were also compared. The results of the study indicated that the LN2 system (LN2 flow rate: 20.5 kg/h; average gas temperature: –85C) had no adverse effect on the quality of the fruits, and improved the cooling coefficient of the air cooling process by 40%. Hence, judicious design of the system and control of exposure time would help in realizing the potential of LN2 in precooling operations for fruits, which would be practically useful in technologies like control atmosphere storage system in particular. PRACTICAL APPLICATIONS Liquid nitrogen (LN2) has ample potential as a refrigerant because of its excellent refrigeration capacity. The use of LN2 in cooling of horticultural produce is especially beneficial in techniques like controlled atmosphere storage, where it is desirable to have a lower oxygen concentration in the storage space. Because LN2 cooling has a high expansion ratio, during its vaporization, it also displaces the oxygen gas from the storage space. However, the use of LN2 as a refrigerant in precooling operations for fruits and vegetables is limited because of concerns of the very cold temperature of the cryogenic liquid resulting in chilling injury to the produce. The present study helps to address the same concerns and proves that if the system is so designed to avoid direct contact between LN2 and the fruits, its refrigerant potential can be successfully tapped.

Cardamom flavoured dairy beverage prepared using standardized method was carbonated in glass bottles. Carbonation at 50 psi pressure for 30 s was recommended. The pasteurized flavoured drink, carbonated or otherwise was evaluated for sensory, chemical and microbial quality during its refrigerated storage. The uncarbonated control samples were found to be sensorily acceptable up to 14 days, while the carbonated beverage remained acceptable up to 30 days. Carbonation of drink significantly affected the pH and acidity of product without reducing its acceptability. Carbonation resulted in inhibition of microbes, the effect was pronounced on psychrotrophic count. There was a linear but marginal increase in the pH of the carbonated samples till the 17(th) day of storage; the values diminished thereafter. The carbonated samples also had significantly reduced contents of FFA and soluble nitrogen compared to that of uncarbonated control samples as storage progressed beyond 10 days and this was attributed to inhibited microbial growth.