MOISTURE LOSS AS RELATED TO HEATING UNIFORMITY IN MICROWAVE PROCESSING OF SOLID FOODS

Moisture loss due to internal evaporation and its relationship to nonuniformity of heating in microwave reheating of high moisture solid foods was studied. A simple heat and mass transfer model was developed that excluded diffusional limitations of moisture movement. Microwave absorption and some dielectric and thermal properties were measured as input parameters to the model. Effect of varying microwave penetration with moisture level and temperature was included. For smaller total moisture loss, typical for a reheating application, predictions of total moisture loss and temperatures matched well with experimental data. Most of the moisture loss occurred from the edges due to higher temperature at these locations. Uniformity of heating to achieve a given average temperature is the key variable controlling total moisture loss. When starting from a frozen material, heating is much more nonuniform, leading to a greater moisture loss. As surface area increases for a given volume, uniformity of heating increases and the total moisture loss reduces. This simple model can be an effective tool in computer-aided optimization of food products and processes.     

EFFECT OF HEATING TEMPERATURE AND MICROWAVE PRETREATMENT ON THE FORMATION OF SUGARS AND VOLATILES IN JEWEL SWEETPOTATO

Experiments investigating changes in the concentration of individual sugars in sweetpotato storage roots with cooking and their relationship to the formation of volatile compounds were conducted. During heat treatment maltose concentration increased from 0.03% fresh weight at 25C to 4.33% at 80C, at which temperature maximum synthesis occurred. Microwave pretreatment (2 or 4 min) resulted in a significant decrease in amounts of maltose and volatiles formed. At 80C, approximately 80% of maltose synthesis was inhibited when pretreated With microwaves. Adding maltose into microwave pretreated samples and then cooking in a convection oven restored most of the volatile profile with the exception of phenylacetadelhyde. It was concluded that maltose represents a primary precursor for many of the volatile compounds emanating from baked ‘Jewel’ sweetpotatoes and the formation of these volatiles appears to involve both enzymatic and thermal reactions.     

DEVELOPMENT OF A PHOTOGRAPHIC SCALE FOR THE VISUAL EVALUATION OF APPLE STRIPE DENSITY1

This research developed a photographic scale for the evaluation of stripe density for 5 apple cultivars (Carousel, 8M-15-10, Fuji, Gala, and Jonagold) using a series of two experiments. In Experiment 1, subjects were able to significantly discriminate and reproducibly score the stripe density of apples using unstructured graphic line scales. Photographs of selected apples were then labelled with the corresponding mean scores and used as visual references for Experiment 2. In Experiment 2, subjects reproducibly evaluated the stripe density of apples using structured line scales (anchored with 3 or 5 photographic references), with similar mean scores from the 3- or 5-point scales. Subject differed very little in their variances reflecting the potential usefulness of these line scales for commercial evaluation of apple stripe density in whole apples.     

HEATING UNIFORMITY AND RATES IN A DOMESTIC MICROWAVE COMBINATION OVEN

Physics-based modeling complemented with magnetic resonance imaging (MRI) for validation can provide a novel means to understand and thereby optimize combination heating processes. The objectives of this study were to compare heating patterns in a combination of radiant, forced air and microwave oven measured by MRI with those predicted by coupled electromagnetics-heat transfer model; quantify speed and uniformity of heating for the different combination modes; determine the effect of food dielectric properties on heating patterns; and delineate the nature of individual heating modes and their combinations. The modes of radiant heating through heating elements and forced convection by fan led to a more uniform heating compared with the faster (but less uniform) heating method provided by the microwaves. Combination methods were faster than radiant, forced-air and microwave-only heating. Although the speed of heating increased appreciably for combination modes, the nonuniformity of heating did not increase as much.

PRACTICAL APPLICATIONS

The results from the study can be used to develop design recommendations/guidelines for combination heating for different thermal processes such as baking, broiling, roasting and reheating of different materials, grouping them based on their properties. The research can benefit the consumers, food services and equipment manufacturers to understand the combination heating process in a better way and to, thereby, use it efficiently. Without a fundamental understanding of the effect of various combinations, optimization of heating can be intractable. The fundamental approach used in this study would, therefore, help consumers and food services in preparation of safe and high-quality foods through combination heating. The work would also help equipment manufacturers in optimizing the designs of combination-heating ovens.     

DEVELOPMENT OF A VOCABULARY FOR PROFILING APPLE JUICES

A protocol for selecting an apple juice lexicon and for training a company panel was developed, using a series of 21 ‘taste’ sessions. Individual assessment, round‐table discussion and consensus were used to identify reference standards for six aroma and 11 flavor attributes and 13 ‘off ‘notes. Duo‐trio tests were used to test the ability of the panelists to recognize the references and confirm their appropriateness in describing the attribute. When panelists' mean scores for the references were placed as anchors on the line scales, panel performance was improved. The development process not only served to train the panel, but was a ‘team’ building experience which benefited the company at large.     

ELECTRICAL CONDUCTIVITY of APPLE and SOURCHERRY JUICE CONCENTRATES DURING OHMIC HEATING

Ohmic heating is based on the passage of electrical current through a food product that serves as an electrical resistance. In this study, apple and sourcherry concentrates having 20–60% soluble solids were ohmically heated by applying five different voltage gradients (20–60 V/cm). the electrical conductivity relations depending on temperature, voltage gradient and concentration were obtained. It was observed that the electrical conductivities of apple and sourcherry juices were significantly affected by temperature and concentration (P < 0.05). the ohmic heating system performance coefficients (SPCs) were defined by using the energies given to the system and taken up by the juice samples. the SPCs were in the range of 0.47–0.92. the unsteady‐state heat conduction equation for negligible internal resistance was solved with an ohmic heating generation term by the finite difference technique. the mathematical model results considering system performance coefficients were compared with experimental ones. the predictions of the mathematical model using obtained electrical conductivity equations were found to be very accurate.     

USE OF APPLE POMACE AS A SOURCE OF DIETARY FIBER IN WHEAT BREAD

Chemical analysis of apple pomace revealed that it contains 29.4% neutral detergent fiber and 13.0% pectin. Pomace-flour blends were prepared by incorporating 2, 5, 8 and 11% pomace in wheat flour. Blends were evaluated for their bread making quality. Water absorption increased with the increase of pomace in the blends. Neutralizing the acidity of pomace blended dough did not change the water absorption significantly. As the percentage of pomace in blends increased from 0 to 11, a reduction of 42.8% in loaf volume was observed but neutralization of pomace acidity in dough resulted in only 26.6% reduction in volume under similar conditions. On the other hand loaf weight of the breads, prepared from blends with 11% pomace under unneutralized and neutralized conditions, increased by 7.0 and 3.1%, respectively. With increase of pomace percentage in blends up to 11, the bread firmness increased from 3N in control to 12 and 10N respectively, in unneutralized and neutralized pomace blended dough. Blending of pomace (0–11%) increased baking time from 20 min for control to 33 min for unneutralized and 27 min for neutralized blends. Sensory evaluation of the product revealed that breads containing up to 5% pomace were acceptable.     

EVALUATION OF MALONALDEHYDE AS A MARKER OF OXIDATIVE RANCIDITY IN MEAT PRODUCTS

Quantification of malonaldehyde as a marker of lipid oxidation in comminuted meat systems, with or without additives, by a distillation and an extraction procedure was investigated. Each method had its own benefits and drawbacks. The extraction procedure generally afforded more realistic results. However, presence of colored additives such as the cooked cured-meat pigment, as well as dispersed lipids in the extracts, interfered with accurate determination of the colored chromogen between malonaldehyde and the 2-thiobarbituric acid (TBA) reagent. On the other hand, the distillation procedure afforded higher TBA values as compared to the extraction method since decomposition of labile hydroperoxides occurred. Addition of antioxidants to the mixtures prior to distillation proved beneficial in some cases. In the presence of residual nitrite, addition of sulfanilamide to the mixture prior to distillation prevented underestimation of malonaldehyde presumably by inhibiting its nitrosation.     

RANCIDITY DEVELOPMENT IN A FISH MODEL SYSTEM AS AFFECTED BY PHOSPHOLIPIDS

Blood components demonstrated the ability to oxidize their own lipids. Blood plasma developed strong oxidation odor during storage apparently due to oxidation of its lipid components. Rancid odor and substantial thiobarbituric acid reactive substances (TBARS) development occurred in shaken solutions of trout blood containing approximately 0.01% lipid. When whole blood was added to washed cod muscle that was taken through a lipid reduction process, rancid odor still occurred during storage. Having at least six times more membrane phospho-lipids present did not enhance the rate or extent of rancidity development during storage of washed cod containing added blood. Contrary to sensory data, TBARS formed more rapidly in the reduced lipid washed cod compared to the washed cod containing approximately 0.6% lipid. The TBARS formation was greater in the reduced lipid washed cod than in the washed cod when expressed on a lipid basis but not when expressed on a wet weight basis. The lack of rancidity and TBARS development when hemolysate was added to a myosin preparation suggested that at least trace amounts of lipid were required for rancidity to occur. Results from these experiments indicate that rancid odor and extensive lipid oxidation can occur at remarkably low levels of fish lipid.     

"DELICIOUS PILAFA" APPLE DENSITY CHANGES AS A QUALITY INDEX OF MASS LOSS DEGRADATION DURING STORAGE

ABSTRACT

Since many years, the mass density of many agricultural products has been used as a quality‐sorting criterion, and automatic machines have been developed for that purpose. According to the literature, apple flesh density seems to be related to flesh stiffness, but this behavior is not common among all cultivars. However, there is a lack of information on the evolution of apple density during storage. This study aims to investigate changes of “Delicious Pilafa” apple density during storage. Fruits have been preserved at 0, 10 and 16C. Experiments have been repeated for three successive storage periods. Linear equations between density and mass loss have been developed for two ranges of storage temperatures, 0–10C and 10–16C. Moreover, an efficient multifactor linear equation that relates density to storage time and mass loss has also been calculated. “Delicious Pilafa” apples are characterized by a high mass loss rate during storage. Thus, the relationships developed in this study could be useful for quality assessment of stored fruits according to their mass loss.

PRACTICAL APPLICATIONS

Mass loss of “Delicious pilafa” apple during storage can be estimated via fruit density and storage time using the developed equations that refers to a variety of storage conditions. Fruit density can be easily measured as well as storage time can be accurately estimated at a certain moment of storage. Such mass loss correlation is important for “Delicious pilafa” apples, characterized from high mass loss rates during storage and thus this prediction procedure could be very useful as an objective quality criterion during storage. Equations that relate mass loss and storage time with fruit density could be also useful for the estimation of fruit's volume. This is particularly important for respiration rate measurements, where fruits volume is required. Using such relations the estimation of volume is feasible only with weighting and without immersing fruits in water that could affect respiration activity and favor spoilage development.

     

DEVELOPMENT OF A BLENDED NONALCOHOLIC BEVERAGE COMPOSED OF COCONUT WATER AND CASHEW APPLE JUICE CONTAINING CAFFEINE

ABSTRACT

In this work, the stability of a blended beverage composed by coconut water and clarified cashew apple juice (“cajuina”) is presented. The physicochemical, microbiological and sensory stability of a blended nonalcoholic beverage composed of coconut water and cajuina (80:20 v/v) were evaluated during 6 months. The results showed that the beverage presented good stability in all analyzed parameters except for vitamin C, which presented a loss of about 80% of the initial content. The beverage color also presented changes during the storage time. Despite these alterations, the product acceptance during the storage period did not show any rejection.

PRACTICAL APPLICATIONS

The development of blended beverages is a good way of improving the nutritional quality of traditional products. By mixing two or more kinds of fruits, a product with more vitamins and minerals and with different sensory and flavor characteristics when compared to the raw materials is obtained. In the present work, coconut water and cashew apple juice were mixed to obtain a different product combining the nutritional components from both fruits. The blended beverage combines the high vitamin C content of the cashew apple juice with the high mineral level of the coconut water. Caffeine was also added conferring stimulating properties to the product. The product acceptance was evaluated by sensory analysis and presented good acceptance until 6 months of storage at room temperature, presenting the required characteristics for a commercial product.