Quality and textural behaviour of par-baked and rebaked cake during prolonged storage

The effect of par-baking and refrigerator storage on the quality of cake was investigated. Quality evaluation of rebaked cakes was performed by using physical, chemical and instrumental texture profile analysis. Cakes were par-baked for 15, 20 and 25 min at 175 °C and then they were stored at refrigerator temperature (4 °C) for 30, 60 and 90 days, wrapped with two polyethylene bags. After storage, par-baked cakes were rebaked at 175 °C and were subjected to analysis. Par-baking and intermediate storage time had a significant effect on baking loss, crumb moisture content, colour, symmetry index and textural properties of cake. The increase in the par-baking time led to a decrease in the baking loss and an increase in the moisture content of cake. Specific volume, moisture content, L colour value and symmetry index significantly decreased with increasing intermediate storage time, while baking loss significantly increased. However, regarding the crumb hardness, cohesiveness, springiness, gumminess and chewiness, the results indicated that the best result was obtained when cakes were baked for 15 min at the par-baking stage. Overall, the cakes became firmer, less cohesive and less dry crumb as the intermediate storage time increased, whereas springiness increased.     

Mechanical behavior of heat-treated spruce (Picea abies) wood at constant moisture content and ambient humidity

The mechanical behavior of heat-treated spruce wood was investigated in relation to the mass loss that occurs during thermal treatment. At constant wood moisture content, the strength, failure strain and toughness of wood were reduced by the heat-bath treatment, decreasing with increasing mass loss. The stiffness was unaffected up to a mass loss of about 3%, and thereafter it decreased. The mechanical properties, however, are not only dependent on the mass loss but also on the relative humidity in the heating atmosphere. As a function of mass loss, the inelastic ductility and the inelastic toughness were the lowest when wood was heated in a dry climate, as compared to a moist climate. On the other hand, the mechanical properties of heat-treated wood were tested at constant ambient humidity. In such circumstances, the failure strain and the toughness were still reduced, but the strength and the stiffness were actually improved up to a mass loss of about 2%–3%. The improvement is due to the lower equilibrium moisture content of heat-treated wood when placed in service conditions. As a function of mass loss, wood heated at intermediate relative humidity (in the vicinity of 50%) exhibited the best mechanical behavior, which surprisingly included inelastic ductility. This is believed to be due to some irreversible hydrogen bonding.     

The effect of par‐baking and frozen storage time on the quality of cup cake

The effects of frozen storage and initial baking time of par‐baked cake on baking loss, volume, moisture, colour and textural properties of cake obtained after thawing and rebaking were investigated. Cakes, par‐baked at 175 °C for 15, 20 and 25 min, were stored at ?18 °C for 3, 6 and 9 months. After storage, par‐baked cakes were thawed and rebaked at 175 °C for 10, 15 and 20 min. Baking loss, moisture content, L and +b colour values, firmness, gumminess and chewiness of the resulting full‐baked cakes were significantly affected by both par‐baking and frozen storage time, while specific volume, cohesiveness, springiness and resilience values were significantly affected by frozen storage time. The increase in the time of frozen storage of the par‐baked cake leads to a decrease in the quality of the rebaked cake, namely an increase of baking loss and cake crumb firmness, and a loss in the moisture content and specific volume. Moisture of cake crumb, L and +b colour values, firmness, gumminess and chewiness significantly increased as the par‐baking time increased. However, regarding baking loss, specific volume, moisture content and textural properties, 3‐month intermediate storage at ?18 °C and 20‐min initial baking time gave the best result among the cakes produced by using the two‐step baking procedure.     

High moisture food extrusion

Summary Extrusion at higher moisture contents (> 40%), also known as wet extrusion, is relatively less investigated compared to low and intermediate moisture extrusion. Literature on high moisture food extrusion has been reviewed. Wet extrusion applications utilise twin screw extruders due to their efficient conveying capabilities. Extruders can be used as bioreactors for starch hydrolysis using thermally stable enzymes. This process is usually followed by saccharification inside or outside an extruder to produce a high DE (dextrose equivalent) syrup. Starch-based high moisture extrusion research also reports a few modelling studies. The rheological properties, torque and energy requirements of high moisture extrusion systems are different from those of low and intermediate systems. Other research reviewed includes the extrusion of low-cost plant and animal proteins to manufacture nutritious food products that imitate the texture, flavour, and mouthfeel of meat.     

A chromogenic medium for the detection of yeasts with beta-galactosidase and beta-glucosidase activities from intermediate moisture foods

A selective and differential solid medium for the specific detection of some common yeasts frequently causing spoilage in intermediate moisture foods is described. The principle of the method is based on the detection of two enzymes, beta-glucosidase and beta-galactosidase, using the chromogenic substrates salmon-Gluc and X-Gal. Over 140 yeasts and bacteria were tested, and Debaryomyces hansenii and Kluyveromyces marxianus strains produced salmon and dark blue colonies, respectively, thus permitting their clear discrimination from other yeasts common in intermediate moisture foods. The medium was very satisfactory when intermediate moisture foods were tested.     

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.     

Water barrier properties of treated-papers and application to sponge cake storage

Water barrier properties of three treated papers and of one plastic film were compared and the potential of these packaging films to prevent moisture loss from a sponge cake during storage in standard conditions (25 °C and 50% relative humidity gradient) was evaluated. Sorption isotherms were established at 25 °C for both sponge cake and papers, from which diffusivity values in papers were determined for the whole range of A_w. Permeability of packaging films was determined in standard conditions. Water sorption was close for all papers, regardless of their treatment, whereas water diffusivity was reduced by coating or calendering. Water vapor permeability in papers was controlled by diffusivity which was characterized by a two-phases (vapor then bulk water state) mechanism. Calendered-coated papers and plastic film were both adapted to prevent moisture loss from intermediate moisture foods such as a sponge cake during usual storage time.     

ANTIOXIDANT EFFECTIVENESS IN INTERMEDIATE MOISTURE CONTENT MODEL SYSTEMS

The effectiveness of antioxidants was studied in methyl linoleate-carbohydrate model systems at the intermediate moisture content. Systems showing sorption hysteresis were used in the range of A_w0.68–0.84. Metal chelating agents were found to be more effective than free radical chain terminators. The antioxidant effectiveness of EDTA (a chelator) was greater in the higher moisture desorption systems since more would be expected to be in solution. The work also showed that metal catalyst activity is responsible for the rapid oxidation rates in intermediate moisture systems as compared to dry systems.     

Enzyme activities during post-harvest storage of kolanut (Cola nitida,Schoot and Endlicher)

The activities of polyphenol oxidase, peroxidase and catalase were determined in extracts of kolanut,Cola nitida stored for 3 months. Enzyme activities measured in nut extracts at the early stages of storage (0–30 days of storage) were not significantly lower than those present in extracts of the fresh unstored nuts. The activities of polyphenol oxidase, peroxidase and catalase measured in the stored kolanut extract were decreased at the intermediate (30–60 days of storage) and mature (60–90 days of storage) periods. Weight changes due to moisture loss during the storage period were also observed. Weight and moisture losses were high during the early storage period and weight loss was steady during the mature storage period. These changes in activities play a significant role in the deterioration of kolanut in storage.     

Loss of structure in freeze-dried carbohydrates solutions: Effect of temperature,moisture content and composition

During processing and storage, dehydrated food materials are subject to changes in their structure. Terms used to describe these changes, which are due to the same basic phenomena, vary from process to process. Thus, during freeze-drying, loss of structure is called “collapse”, while during storage, phenomena related to viscous flow of the dried powder matrix are termed “stickiness”. This loss of initial structure often results in the loss of desirable product qualities, though in some cases controlled manipulation of these changes is used to produce improved products. In freeze-drying, collapse of capillaries in the dry layer results in puffing and loss of desirable structure. In dehydrated powders “stickiness” leading to caking and other defects is also a result of collapse phenomena. The collapse temperature of freeze-dried orange juice and carbohydrate solutions was investigated as a function of moisture content and sample composition. It was observed that collapse temperatures decreased as the sample moisture content increased. Mixtures of materials collapsed at a temperature intermediate to that of the individual components. The consequences of these observations to a number of food processes are discussed.     

NUTRITIONAL, PROXIMATE, AND MICROBIAL CHARACTERISTICS OF PHOSPHATE PROCESSED SEA SCALLOPS (PLACOPECTEN MAGELLANICUS)

Sea scallop adductor muscles were used to evaluate six scallop processing methods with regards to changes in moisture content, nutritional equivalency, and total plate counts. Sodium tripolyphosphate (STP) reduced the rate of moisture incorporation, enhanced scallop moisture binding capacity and maintained a degree of antimicrobial capacity. Scallop moisture content increased with processing time. Short processing times using a higher concentrated STP solution performed as well, or better, in binding moisture and reducing bacteria than longer processing times using a lower concentrated STP solution. Increasing moisture content decreased nutrient levels on a per weight basis. Nutrients most affected by increasing moisture content were protein, niacin, calcium, and vitamin B₁₂. Moisture loss due to freeze/thaw or cooking concentrated some nutrients (protein and minerals), while contributing to the loss of water-soluble nutrients. The use of STP lowered scallop drip loss, which in turn, reduced nutrient loss.     

The role of lipids and glycerol in determining the shelf-life of glycerol desorbed intermediate moisture meat products

During storage of glycerol desorbed intermediate moisture beef at 38°C the marked loss of eating quality, demonstrated by increasing loss of nitrogen solubility in sodium dodecyl sulphate (SDS) plus β-mercaptoethanol, loss of haemoprotein character, decrease in pH and the formation of water-soluble hydroxyproline containing fragments, is not markedly affected by the presence of oleic acid and/or butylated hydroxytoluene. In addition, gas-liquid chromatographic analysis of the lipid fractions suggests that, in these meats, the relative composition of the neutral phospholipid fractions does not change to any marked extent during storage. However, the TBA and peroxide values, which are very high in the freshly prepared meats, do decrease quite markedly during storage. Consideration of these results suggests that, in glycerol desorbed meats, glycerol oxidation products are the major reactants leading to loss of eating quality.     

Enzyme activities during post-harvest storage of kolanut (Cola nitida, Schoot and Endlicher)

The activities of polyphenol oxidase, peroxidase and catalase were determined in extracts of kolanut,Cola nitida stored for 3 months. Enzyme activities measured in nut extracts at the early stages of storage (0–30 days of storage) were not significantly lower than those present in extracts of the fresh unstored nuts. The activities of polyphenol oxidase, peroxidase and catalase measured in the stored kolanut extract were decreased at the intermediate (30–60 days of storage) and mature (60–90 days of storage) periods. Weight changes due to moisture loss during the storage period were also observed. Weight and moisture losses were high during the early storage period and weight loss was steady during the mature storage period. These changes in activities play a significant role in the deterioration of kolanut in storage.     

Nutritive value of high moisture alfalfa hay preserved with urea

Urea (2 and 4%) was added to high moisture hays and compared with untreated wet or dry hays. Means for bale temperatures (degree C) for 1 wk postharvest were highest for wet control (41.2), lowest for dry control (31.4), and intermediate for urea treatments (36.7). By 4 wk postharvest, all temperatures were equal. Protection from molding was most effective for 4% urea, and 2% urea was superior to wet control. By 4 mo postharvest, CP for low urea had decreased due to NH3 loss, and CP for wet control had increased due to DM loss, so they were not different. Initially, ADF was similar for the hays, but after 4 mo storage the wet control was highest (41.7%), the dry control lowest (36.0%), and urea treatments intermediate. Lignin and NDF followed similar trends. In vitro DM digestibilities were highest for the wet control at harvest but lowest at 120 d with high urea and dry control greater than low urea. Feed intakes and milk yields in lactating cows fed the hays were not different. These data show that addition of 2 or 4% urea improved quality of hay baled at about 25% moisture; high urea was more effective than low urea.     

Ascorbic acid loss and sensory changes in intermediate moisture pineapple during storage at 30–40°C

Kinetics of ascorbic acid loss as a function of storage temperature (30, 35 and 40°C) and water activity of intermediate moisture pineapple slices at a _W of 0.92, 0.95 and 0.97 was modelled. Loss was faster at higher a _W but storage temperatures of 30 - 40°C had little effect at the same a _w. Colour changes were larger than flavour changes. Spoilage was only a problem at high a _w.     

Effect of Surface Active Agents on Water Activity of IM Food Solutions

Some recent literature results indicate that the water activity (a_w) of intermediate moisture food model solutions increased as the surface tension decreased by addition of surfactants. Consequently, it was suggested that in the processing of intermediate moisture foods, ingredients which result in the reduction of surface tension should be avoided to attain low a_w. The results obtained in this work do not confirm those reported by Chen and Karmas (1979); instead it is concluded that the effect of surface tension on the a_w of food solutions is such that it needs not be considered, at least for the large majority of research or development applications in the food area.     

Cellulose-based edible films and their effects on fresh beans and strawberries

 Cellulose-based edible films were applied to fresh beans and strawberries. The moisture loss from these food was measured following the application of films of varying composition under different conditions. The effects of the method of application of film solution, the amounts of polyethylene glycol (PEG), stearic acid (SA), palmitic acid (PA) and lauric acid (LA) in the film, the molecular weights of methyl cellulose (MC) and PEG and, finally, the relative humidity of the environment on moisture loss from fresh beans and strawberries coated with films were investigated. The brushing method for the application of film solution to the foods was found to be better than wrapping and dipping methods in terms of reducing the moisture loss. Recommended amounts of PEG-400 and fatty acids in film solution to reduce moisture loss from foods were found to be 11 ml and 40 g per 100 g MC-20000, respectively. A slight decrease in moisture loss was observed when PEG-400 and MC-20000 in the film solution were replaced by PEG-1000 and MC-41000, respectively. Finally, it was found that moisture loss from fresh beans and strawberries coated with films decreased as the relative humidity of the environment in which they were kept was increased. Received: 19 December 1996 / Revised version: 20 May 1997     

Effects of frying parameters on physical changes of tapioca chips during deep-fat frying

The interrelationships of the effects of frying time, oil temperature, and initial moisture content on moisture loss, oil absorption, and linear expansion of a tapioca starch chip half-product during deep-fat frying have been studied. Both oil absorption and linear expansion were affected, in different ways, by moisture loss. Oil absorption was essentially a quantitative water replacement process. On the other hand, linear expansion occurred as a result of rapid vaporization of water in the initial stages of frying, but reached a plateau before maximum moisture loss. Critical frying times, temperatures, and initial moisture contents, below which virtually no physical change occurred, were observed. The optimum set of frying parameters for maximum linear expansion appears to be a frying time of 40 s, an oil temperature of 200°C, and an initial moisture content of 15% (dry basis).     

MATHEMATICAL MODELING OF HEAT AND MOISTURE TRANSFER-RELATED PROPERTIES OF INTERMEDIATE MOISTURE APPLIES

Mathematical models for heat and moisture transfer-related properties of intermediate moisture apples were developed. The models of thermal properties were based on a linear dependence of thermal conductivity on temperature and moisture content, a logarithmic dependence of bulk density on moisture content, and a linear dependence of specific heat on moisture content. The effect of moisture content and temperature on moisture diffusivity was modeled by an exponential relationship. The sorption data were adequately fitted by the Modified Henderson's equation.     

Characterization and Modeling of Dielectric Properties of Turkey Meat

ABSTRACT: The dielectric properties of turkey meat at water activities of 0.84 to 0.98 were measured at 2450 and 915MHz. Equations were developed as a function of temperature, moisture, water activity, and ash, and compared to literature equations. Unexpected results were: as the water activity decreased or ash increased, the dielectric constant increased with temperature, and dielectric loss factor of reduced moisture samples was determined by moisture not ash. It is theorized that the effect of temperature on dielectric constant is a function of the ratio of bound to free water. Glycerol did not affect the dielectric properties, while lactic acid decreases them by promoting water loss during protein denaturation.