Thermal oxidation of model molecules to reveal vegetable oil polymerization studied by NMR spectroscopy and self-diffusion

Oxidative polymerization of plant oils and lipids is poorly understood yet widely encountered. Oils and fats are renewable resources providing biofuels and polymers. Oil oxidation is accelerated at high temperatures, typically above 110°C, where triacylglycerides are converted into toxic compounds and viscous deleterious polymers. Polymerization of mono-unsaturated oil (210°C, 3 h, open to air) was investigated by comparing four similar sized molecules with different functional groups: oleic acid, methyl oleate, trans-7-tetradecene, and stearic acid. Non-volatile products identified by NMR spectroscopy are minor ketones for saturated fatty acid (stearic acid), epoxides for acyl chains without acid groups (methyl oleate, tetradecane) and copious oligomerization, through ester cross-links, for acyl chains with acid, and olefinic groups (oleic acid). Long range C H coupling clearly shows ester (not ether) cross-links, contradicting long-held beliefs. Chain fragmentation also occurs for heated oleic acid as revealed by formation of a species with a methylene group bonded to oxygen of an ester,  CH₂ O C(O) . Large size (slow diffusion) of the first oligomer (trimer) formed from oleic acid, used to represent hydrolyzed vegetable oil, was evidenced by DOSY (diffusion-ordered spectroscopy). Combined NMR results show oligomers found in heated oleic acid are fatty acid estolides. Model oil reactions demonstrate why olefin and carboxylic acid groups are required for polymerization.     

Glycerol Esters from Real Waste Cooking Oil Using a Robust Solid Acid Catalyst

Notwithstanding the food-for-fuel debate, turning waste cooking oil and fat (WCO) into a valuable product is a classic example of green chemistry. We demonstrate that sulfated zirconia and lanthanum-supported sulfated zirconia are good catalysts for the esterification of WCO free fatty acids (FFAs) with glycerol, giving high-value monoglycerides. Various catalysts were first screened using palmitic acid as a model FFA. Subsequently, six 10-kg batches of actual WCO were collected from commercial cookeries over a period of 28 weeks, pre-treated in a purpose-built decanter and esterified with industrial grade glycerol using heterogeneous catalysis. Good yield and turnovers were obtained. The pre-treatment stage and the catalytic esterification experiments are described and discussed.     

Enhanced Anthocyanin Extraction from Red Cabbage Using Pulsed Electric Field Processing

Abstract: This study was conducted to evaluate the effect of pulsed electric field (PEF) treatment on anthocyanin extraction from red cabbage using water as a solvent. Mashed cabbage was placed in a batch treatment chamber and subjected to PEF (2.5 kV/cm electric field strength; 15 μs pulse width and 50 pulses, specific energy 15.63 J/g). Extracted anthocyanin concentrations (16 to 889 μg/mL) were determined using HPLC. Heat and light stabilities of the control and PEF-treated samples, having approximately the same initial concentrations, were studied. PEF treatments enhanced total anthocyanin extraction in water from red cabbage by 2.15 times with a higher proportion of nonacylated forms than the control (P < 0.05). The heat and light stabilities of the PEF-treated samples and control samples were not significantly different (P > 0.05). Practical Application: An innovative pretreatment technology, pulsed electric field processing, enhanced total anthocyanin extraction in water from red cabbage by 2.15 times. Manufacturers of natural colors can use this technology to extract anthocyanins from red cabbage efficiently.     

Application of a dry heat treatment to enhance the functionality of low-heat nonfat dry milk

Nonfat dry milk is a valuable food and ingredient because it contains proteins, fat, carbohydrates, minerals, and vitamins. When manufactured, this product is classified into high heat (HH) or low heat (LH) depending on the pre-heat treatment used in pasteurization. Radio frequency dielectric heating, if used alone or as part of a dry heat technology, may induce component interactions in milk powders, which could alter or improve functionality. To pursue this objective, LH was subjected to radio frequency dielectric heating to 80, 85, and 90°C with a subsequent hold period of 60 or 90 min in an oven, set at the designated temperature, 80, 85, or 90°C, assessed for functionality in liquid and gel systems, cooled, and subsequently compared with LH and HH. The functionality assessment included heat stability and foaming, emulsion, and gelling properties. For foaming, LH presented a statistically lower overrun and foam stability compared with all dry-heated LH. The LH dry-heated at ≥85°C exhibited significantly greater foaming capacity than did the LH. Emulsification properties were not significantly different as a function of dry heating compared with LH. As gels, water-holding capacity was greater and syneresis was significantly less for all gels made with the dry-heated LH at <85°C. Gel firmness and cohesiveness were not affected by dry heating. The heat coagulation time at native pH was significantly greater for LH that were dry-heated for 90 min compared with LH. At adjusted pH (6.4 to 7.2), the heat stability was improved if the LH was dry-heated. The dry-heated LH had significantly less foaming properties, but greater emulsion activity compared with the HH. Overall, the dry heat treatment conditions of this study did not result in acid-induced gels with equivalent properties as gels made with HH. Syneresis was similar for all gels except for those made from the dry-heated LH to 90°C and held for 60 min, as this gel had significantly more syneresis than did the gels made from HH. However, the heat stability of dry-heated LH at native, 6.8, 7.0, and 7.2 pH was greater compared with the heat stability of HH. The application of a dry heat treatment enhanced the functional properties of LH, opening the opportunity to develop food products that can use this modified nonfat dry milk such as ice cream, bakery, and meat products.     

Validation of process technologies for enhancing the safety of low-moisture foods: A review

The outbreaks linked to foodborne illnesses in low-moisture foods are frequently reported due to the occurrence of pathogenic microorganisms such as Salmonella Spp. Bacillus cereus, Clostridium spp., Cronobacter sakazakii, Escherichia coli, and Staphylococcus aureus. The ability of the pathogens to withstand the dry conditions and to develop resistance to heat is regarded as the major concern for the food industry dealing with low-moisture foods. In this regard, the present review is aimed to discuss the importance and the use of novel thermal and nonthermal technologies such as radiofrequency, steam pasteurization, plasma, and gaseous technologies for decontamination of foodborne pathogens in low-moisture foods and their microbial inactivation mechanisms. The review also summarizes the various sources of contamination and the factors influencing the survival and thermal resistance of pathogenic microorganisms in low-moisture foods. The literature survey indicated that the nonthermal techniques such as CO₂, high-pressure processing, and so on, may not offer effective microbial inactivation in low-moisture foods due to their insufficient moisture content. On the other hand, gases can penetrate deep inside the commodities and pores due to their higher diffusion properties and are regarded to have an advantage over thermal and other nonthermal processes. Further research is required to evaluate newer intervention strategies and combination treatments to enhance the microbial inactivation in low-moisture foods without significantly altering their organoleptic and nutritional quality.     

Modeling the effect of temperature on growth of Salmonella in chicken

Growth data of Salmonella in chicken were collected at several isothermal conditions (10, 15, 20, 25, 28, 32, 35, 37, 42, and 45 degrees C) and were then fitted into primary models, namely the logistic model, modified Gompertz model and Baranyi model. Measures of goodness-of-fit such as mean square error, pseudo-R(2), -2 log likelihood, Akaike's information, and Sawa's Bayesian information criteria were used for comparison for these primary models. Based on these criteria, modified Gompertz model described growth data the best, followed by the Baranyi model, and then the logistic model. The maximum growth rates obtained from each primary model were then modeled as a function of temperature using the modified Ratkowsky model. Pseudo-R(2) values for this secondary model describing growth rate obtained from Baranyi, modified Gompertz, and logistic models were 0.999, 0.980, and 0.990, respectively. Mean square error values for corresponding models were 0.0002, 0.0008, and 0.0009, respectively. Both measures clearly show that the Baranyi model performed better than the modified Gompertz model or the logistic model.     

Challenges in Radiofrequency Pasteurization of Shell Eggs: Coagulation Rings

A total of 50 different configurations of simple radiofrequency (RF) heating at 27.12 MHz of a shell egg were simulated using a finite element model with the purpose of pasteurizing the egg. Temperature‐dependent thermal and dielectric properties of the yolk, albumen, and shell were measured, fitted, and introduced into the model. A regression equation that relates the top electrode voltage to the gap between the electrodes and vertical position of the egg was developed. Simulation and experimental results had good agreement in terms of temperature deviation (root mean squared error ranged from 0.35 °C to 0.48 °C) and both results demonstrated the development of a “coagulation ring” around the air cell. The focused heating near the air cell of the egg prevented pasteurization of the egg due to its impact on quality (coagulation). Analysis of the electric field patterns offered a perspective on how nonuniform RF heating could occur in heterogeneous food products. The results can be used to guide development of RF heating for heterogeneous food products and further development of RF pasteurization of eggs.     

Multiphysics Modeling of Microwave Heating of a Frozen Heterogeneous Meal Rotating on a Turntable

A 3‐dimensional (3‐D) multiphysics model was developed to understand the microwave heating process of a real heterogeneous food, multilayered frozen lasagna. Near‐perfect 3‐D geometries of food package and microwave oven were used. A multiphase porous media model combining the electromagnetic heat source with heat and mass transfer, and incorporating phase change of melting and evaporation was included in finite element model. Discrete rotation of food on the turntable was incorporated. The model simulated for 6 min of microwave cooking of a 450 g frozen lasagna kept at the center of the rotating turntable in a 1200 W domestic oven. Temperature‐dependent dielectric and thermal properties of lasagna ingredients were measured and provided as inputs to the model. Simulated temperature profiles were compared with experimental temperature profiles obtained using a thermal imaging camera and fiber‐optic sensors. The total moisture loss in lasagna was predicted and compared with the experimental moisture loss during cooking. The simulated spatial temperature patterns predicted at the top layer was in good agreement with the corresponding patterns observed in thermal images. Predicted point temperature profiles at 6 different locations within the meal were compared with experimental temperature profiles and root mean square error (RMSE) values ranged from 6.6 to 20.0 °C. The predicted total moisture loss matched well with an RMSE value of 0.54 g. Different layers of food components showed considerably different heating performance. Food product developers can use this model for designing food products by understanding the effect of thickness and order of each layer, and material properties of each layer, and packaging shape on cooking performance.     

Mathematics Research in India Today: What Does the Literature Reveal?

Mathematics research in India, as reflected by papers indexed inMathsci 1988–1998, is quantified and mapped. Statistics, quantum theory and general topology are the three subfields contributing the most to India's output in mathematics research, followed by special functions, economics and operations research, and relativity and gravitational theory. Indian Statistical Institute and Tata Institute of Fundamental Research are the two leading publishers of research papers. Unlike in many other fields, Calcutta publishes the largest number of papers in mathematics, followed by Mumbai, New Delhi, Chennai and Bangalore. West Bengal, Uttar Pradesh, Maharashtra, Tamil Nadu and Delhi are the leading states. Researchers from 257 institutions spread over 134 cities/towns have published 17,308 papers in the 11 years. About 92% of these papers have appeared in 877 journals published from 62 countries. Journals published in the USA, UK and the Netherlands are popular with Indian mathematicians. Of the 36 journals that have published at least a hundred papers, 20 are Indian journals of which only two are indexed in Journal Citation Reports. In all, about 38.5% of papers have been published in Indian journals, as against about 70% in agriculture, 55% in life sciences, 33.5% in medicine and 20% in physics. In the later years, there has been a moderate shift to non-Indian journals. Close to 78% of papers have come from universities and colleges and 13% from the institutions under science related departments. Almost all papers in high impact journals are physics related and most of them have come from institutions under the Department of Atomic Energy. Over 15% of the 9760 papers published during 1993–1998 are internationally coauthored. In all of science, as seen from Science Citation Index, 14% of Indian papers were internationally coauthored in 1991 and 17.6% in 1998. The USA, Canada, and Germany are the important collaborating nations, followed by France, Italy, Japan and the UK. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date.