Effect of processing conditions on proteolysis and taste of dry-cured sausages

 This paper deals with the influence of industrial practices such as use of starters (Lactobacillus sake and Staphylococcus carnosus), preripening (3 days at 5°C) and drying temperatures (8 and 16°C) on proteolysis, ammonia production and the taste of “salchichón”, a traditional Spanish dry-cured sausage lacking surface mould. pH dropped more sharply in the presence of a starter and at a high drying temperature (16°C); preripening did not affect the pH. The highest value for non-protein nitrogen (NPN), 16% of total nitrogen, was observed to occur in samples with the lowest pH (4.7–4.8). Total volatile basic nitrogen (TVBN) increased during drying due to the deaminase activity of internal microbial flora, which was not great (0.5–1.0% of total nitrogen) enough to affect the pH, and significantly in samples showing a larger decrease of pH. The greater proteolysis in samples with starter did not affect the assessors’ taste preference. Assessors clearly preferred those samples without starter that were dried at low temperature (8°C); however, samples with starter showed excellent commercial appearance since they dried more homogeneously. An equilibrium point must be found between acid production and taste. Received: 12 February 1996/Revised version: 24 May 1996     

Effect of Pre-treatment and Drying Method on Colour Degradation Kinetics of Dried Salak Fruit During Storage

Effect of heat treatment on colour stability of dried salak fruit during storage was investigated by using hot air (40–90 °C), heat pump (isothermal and intermittent modes, 26–37 °C) and freeze-drying. Influence of pre-treatment on the colour property was studied as well by blanching the sample at three levels of temperature (50–70 °C). Total colour change (∆E*) was used to assess the colour degradation kinetics and quantify the degree of browning during processing and storage. It was found that the dried pre-treated sample under heat pump isothermal drying recorded the highest ∆E* value during storage followed by non-pre-treated samples under heat pump intermittent drying, freeze-drying, hot air-drying and heat pump isothermal drying. Weibull model is found to better fit the experimental data as compared with zero-order and first-order kinetics models. Analysis on the kinetics constants reveals that the heat treatment could affect the microstructure, water sorption properties and concentration of reacting species of the dried product. This in turn contributes to the colour changes of the dried product during storage.     

Foam-Mat Drying of Plantain and Cooking Banana (<Emphasis Type="Italic">Musa</Emphasis> spp.)

Foaming, reconstitution, and sensory attributes of foam-mat-dried plantain and cooking banana were investigated. Plantain and cooking banana pastes mixed with different concentrations (0.005%, 0.01%, 0.015%, and 0.02%) of glyceryl monostearate (GMS) were whipped, and the resulting foams were air dried at 60°C, 70°C, and 80°C. Physical, chemical, and sensory properties of fresh and reconstituted paste from plantain and cooking bananas were determined. Higher GMS concentration and longer whipping time resulted in lower foam densities. Generally, cooking banana foams showed lower foam density compared to plantain foam. Lower drying temperatures and concentration of GMS resulted in longer drying time. pH (4.41–4.80), titratable acidity (0.06–0.08), and water absorption capacity (56.75–64.02%) of the reconstituted pastes varied with commodity, drying temperature, and %GMS concentration. Fresh and reconstituted pastes showed comparable physical and chemical attributes, while the taste and sensory attributes of fresh plantain and cooking banana pastes were significantly (p < 0.05) better than those of reconstituted pastes.     

Lactic Fermentation Effects on Preservative Qualities of Dendeng Giling

Model “Dendeng giling”, Indonesian non fermented dried beef, was prepared after fermentation with Lactobacillus plantarum as starter and compared with control without starter culture. Inoculated sample was fermented at 30°C 16 hr, Lactobacillus grew from 10⁶ to 10⁸, pH went from 5.71 to 5.2. Micrococcus, Gram-negative bacteria, Pseudomonas, Staphylococcus, and Escherichia coli were inhibited by 98.3%, 77%, 93%, 96% and 77% after fermentation 16 hr. Inoculated samples were tested for inhibiting VBN and TBA value, dissipating residual nitrite and development of redness. Lower pH caused faster drying at 50°C and reduced water activity. The combination of low pH and water activity made possible improvement of preservative quality.     

Type of bacterial starter culture,aging and fermentation effects on some characteristics of inoculated beef sausages

Beef sausage mixes were inoculated with either Pediococcus acidilactici with Staphylococcus xylosus or P. acidilactici with S. carnosus, subdivided and then held for 0, 24, 48 or 72 h at 8–10 °C prior to fermentation. After aging (pre-fermentation holding), the mixes were fermented for 16 h ending at 41 °C. Moisture, protein and fat contents of all sausage mixes did not differ due to holding effects over all starter cultures. The pH of mixes followed the same pattern for all mixes, declining (p < 0.05) from approximately 5.8 to pH 5.2–5.3 at 72 h aging and to 4.4–4.5 after fermentation. Total acidity of the mixes followed an inverse pattern to pH, increasing (p < 0.05) after fermentation although there was no effect due to type of starter culture. Aging had no effect on nonprotein nitrogen (NPN) content as ΔNPN among all cultures. After fermentation, however, sausages held 72 h and inoculated with S. carnosus had higher NPN contents compared to P. acidilactici alone (p < 0.05) and with S. xylosus (p < 0.10). The same effects of starter cultures on changes in total amino acid concentration were observed. Concentrations of individual amino acids showed increases depending on pre-fermentation aging period (0 h versus 72 h) followed by fermentation.     

Drying Temperature and Time Affect Quality of Chinese-style Sausage Inoculated with Lactic Acid Bacteria

Lactobacillus plantarum, Streptococcus thermophilus and a commercial culture (DS-66) were used as starter culture for manufacturing Chinese-style sausage. The influence of drying temperature and time on the growth of lactic acid bacteria (LAB) and on changes in quality were determined. After drying the sausage at 370 and 45°C for 12 hr, the population of LAB had increased from an initial 10⁶ CFU/g to 10⁸ and 10⁷ CFU/g, respectively. The pH value was the lowest for the sausage dried at 37°C. Nitrite residuals decreased rapidly with increased drying time. Starter cultures increased the amino nitrogen level and suppressed ammonia nitrogen production.     

Effect of Processing Methods on Physical,Chemical, Rheological,and Sensory Properties of Okra (<Emphasis Type="Italic">Abelmoschus esculentus</Emphasis>)

Effects of freezing/thawing, sun drying, solar drying, and foam-mat drying on physical, chemical, rheological, and sensory attributes of okra were investigated. Average poured bulk and tapped bulk densities of sun-dried, solar-dried, and foam-mat-dried okra were 800 and 950, 715 and 765, 355 and 367 kg/m³, respectively. Minimum and maximum porosity of sun-dried, solar-dried, and foam-mat dried okra were 55.70% and 62.60%, 50.06% and 53.30%, 60.90% and 62.87%, respectively. Sun-dried and solar-dried okra showed higher L*, a*, and chroma values than frozen/thawed and foam-mat-dried okra. Within a temperature range of 80–40 °C, viscosity of fresh, frozen/thawed, foam-mat-dried, solar-dried, and sun-dried okra were 0.055–0.080, 0.055–0.075, 0.050–0.073, 0.005–0.065, and 0.005–0.022 Nsm⁻², respectively. Sensory evaluation showed no significant difference (p < 0.05) between fresh, frozen/thawed, and foam-mat dried okra in color, aroma, and overall acceptability. Sun-dried and solar-dried okra were significantly poorer (p < 0.05) in color, aroma, taste, and overall acceptability.     

Effect of Air-Drying Conditions on Physico-chemical Properties of Osmotically Pre-treated Pomegranate Seeds

The drying of pomegranate seeds was investigated at 40 °C, 50 °C and 60 °C with air velocity of 2 m/s. Prior to drying, seeds were osmodehydrated in 55 °Brix sucrose solution for 20 min at 50 °C. The drying kinetics and the effects of osmotic dehydration (OD) and air-drying temperature on antioxidant capacity, total phenolics, colour and texture were determined. Analysis of variance revealed that OD and air-drying temperature have a significant influence on the quality of seeds. Both anthocyanin and total phenolic contents decreased when air-drying temperature increased. The radical diphenylpicril-hydrazyl activity showed the lowest antioxidant activity at 60 °C. Both chromatic parameters (L*, C* and h°) and browning index were affected by drying temperatures, which contributed to the discolouring of seeds. The final product has 22%, 20% and 16% of moisture; 0.630, 0.478 and 0.414 of a _w; 151, 141 and 134 mg gallic acid equivalent/100 g fresh matter (FM) of total phenolics; 40, 24, 20 mg/100 g FM of anthocyanins and 46%, 39% and 31% of antioxidant activity, for drying temperatures of 40 °C, 50 °C and 60 °C, respectively. In view of these results, the temperature of 40 °C is recommended as it has the lowest impact on the quality parameters of the seeds. Differential scanning calorimetry data provided complementary information on the mobility changes of water during drying. Glass transition temperature (Tg′) depends on moisture content and as consequence, on drying conditions. In fact, Tg′ of seeds dried at 60 °C (Tg′ = −21 °C) was higher than those dried at 50 °C (Tg′ = −28 °C) or 40 °C (Tg′ = −31 °C) and osmodehydrated seeds (Tg′ = −34 °C). During OD and drying process, the texture of seeds changed. The thickness of seeds shrank by 55% at 60 °C.     

Potentially bioaccessible phenolics,antioxidant capacities and the colour of carrot,pumpkin and apple powders – effect of drying temperature and sample structure

The study aimed to examine carrot, pumpkin and apple powders produced by hot-air-drying (50, 60, 70 °C) of samples with different levels of fragmentation (cut, grated, blended). The drying temperatures and sample structure were shown to be important determinants of the quality of the powders. The best colour stability of carrot, pumpkin and apple was found for the grated sample dried at 70 °C, the blended sample dried at 70 °C and the blended sample dried at 70 °C, respectively. The highest antiradical capacity and reducing power were found for powders obtained after drying the cut samples at 70 °C. Total phenolics and free radical quenchers were well bioaccessible in vitro. In turn, the reducing power was markedly reduced after drying at 50 °C. The analysed powders are a valuable source of concentrated bioactive ingredients, which predisposes them to serve as functional food components.     

Effect of Blanching and Drying Temperature on Polyphenolic Compound Stability and Antioxidant Capacity of Apple Pomace

The effects of blanching and drying treatments on stability, physical properties, and antioxidant activity of apple pomace polyphenols were evaluated. Blanched and unblanched apples were extracted, and the pomace was dried in a cabinet dryer at a speed of 3 m/s at 50 °C, 60 °C, 70 °C, and 80 °C. The color, total phenolics, flavonoids, individual polyphenolic compounds, anthocyanins, and total antioxidant activity were analyzed. The blanching process caused a major retention in color, total polyphenolic content, and total flavonoid content for fresh apple pomace when compared with fresh unblanched pomace. Drying of either fresh blanched or fresh unblanched pomace caused a significant reduction (P < 0.05) in total polyphenol and flavonoid content leading to a reduction in the total antioxidant activity. When compared with the unblanched treatment, drying the blanched pomace at 80 °C resulted in a product with significant amounts of total phenolics, flavonoids, and antioxidant activity. The individual phenolic compounds were significantly increased (P < 0.05) in blanched pomace that was not dried when compared with unblanched samples. Drying blanched apple pomace did not cause a significant change in the concentration of individual polyphenolic compounds, but drying unblanched apple pomace caused a reduction in the concentrations of epicatechin and caffeic acid, with an important reduction in p-coumaric acid at temperatures higher than 60 °C. However, the drying process caused a significant reduction in the antioxidant capacity. Therefore, a combination of blanching and drying processes for apple pomace results in a product that maintains antioxidant capacity.     

Effect of debranching and heat treatments on formation and functional properties of resistant starch from high-amylose corn starches

High-amylose corn starches [(Hylon V (H5) and Hylon VII (H7)] were debranched with pullulanase, followed by autoclaving–storing cycles and drying in an oven (at 50 °C) or freeze-dryer. The samples were autoclaved at 123 and 133 °C and stored at 4 and 95 °C. Molecular weights of the samples decreased and resistant starch (RS) contents increased with increased debranching time. RS contents of H7 samples were higher than those of H5 samples. RS contents of oven-dried samples were higher than those of freeze-dried samples. Debranching caused decreases in DSC peak temperature (T _p) and increases in enthalpy (ΔH) values of H5 and H7. Autoclaving at 133 °C caused higher ΔH values as compared to autoclaving at 123 °C. The solubility and water-binding values of autoclaved-only (control) and autoclaved–debranched (3–48 h) samples and the samples treated with autoclaving–storing cycles after debranching of both H5 and H7 were higher than those of their respective native starches. Debranching of starch samples affected the emulsion capacity of albumin adversely, but improved the emulsion stability of albumin. Cold viscosity values of freeze-dried samples were higher than those of oven-dried samples. Autoclaving–storing cycles after debranching caused decreases in peak, breakdown and final viscosity values.     

Dehydration characteristics of Maesaengi (Capsosiphon fulvescens) in hot-air drying

Maesaengi (Capsosiphon fulvescens) was dehydrated in a single layer at drying air temperatures ranging from 50–80°C in a laboratory scale convective dryer with an air velocity of 0.26 m/s. The effect of drying air temperature on the drying kinetic characteristics was determined. Maesaengi was dried to equilibrium moisture content within 200–600 min under these drying conditions. Drying rate curves of maesaengi showed an initial short period of a constant drying rate, followed by a falling drying rate period. The moisture decrease in the sample during dehydration was well described by the zero-order kinetic model. An Arrhenius-type equation was used to test the effect of temperature on drying rate according to an activation energy value of 29.36 kJ/mol.     

Influence of Oven-Drying Temperature on Physicochemical and Functional Properties of Date Fibre Concentrates

Agri-food by-products rich in dietary fibres may be used as feeds and health foods. Owing to its high fibre content, date flesh could be useful in human nutrition. It is interesting to study the influence of oven-drying temperatures of date fibre concentrates (DFC) on their physicochemical and functional properties for possible use as a potential fibre source in the enrichment of food. DFC from 11 Tunisian date cultivars were dried at different temperatures (40, 50 and 60 °C) and analysed regarding proximate composition (moisture, ash, protein and lipids), physicochemical (water activity (a _w), pH) and functional properties (water holding capacity (WHC), swelling capacity (SC), oil holding capacity (OHC) and emulsifying capacity (EC)). DFC dried at different temperatures showed interesting functional characteristics such as hydration properties, high OHC (2.73–4.60 g oil/g dry fibre) and EC (5.93–12.87%) values. Although drying temperatures promoted little modifications affecting the physicochemical properties of DFC, significant decreases in WHC, SC and EC of DFC were noticed at the highest temperature (60 °C) for most of the date varieties. The observed influence of drying temperature on functional DFC properties calls for the use of low temperature in order to obtain DFC as suitable food ingredient.     

Chemical and bacteriological changes in fish muscle during heating and drying at 30 degrees C

Regularly shaped samples of flesh from a lean fish from temperate waters, cod (Gadus morrhua,) and a fatty fish from tropical waters, hilsa (Hilsailisha), were dried to various extents in a mechanical drier at 30 °C. Similar blocks of muscle were subjected to the same temperature conditions but wrapped to prevent dehydration in order to compare the effect of heating without dehydration. The changes in extractable proteins, non-protein nitrogen, bacterial count, pH and, in the case of hilsa, lipid oxidation are reported. The amount of extractable myofibrillar protein decreases markedly during both heating and drying, the rate being faster for cod than for hilsa and the extra effect of drying over heating alone is different in the two species. The bacterial count increases continuously with time in the case of the heated samples but reaches a steady value and then decreases during drying. Non-protein nitrogen and pH changes are similar to the bacterial changes. There is marked lipid oxidation during both heating and drying, the effect being greater in the dried samples. It is concluded that most of the protein changes during drying are due to the effects of heating rather than dehydration.     

Studies on pasting and structural characteristics of thermally treated wheat germ

In order to utilize wheat germ, a nutrient-dense by-product of wheat milling industry, in various food products, different moist and dry heat treatments were used to stabilize and to investigate its influence on protein sub-unit composition, starch pasting characteristics and structural characteristics. The raw germ contained 11% moisture, 31.4% crude protein, 18.4% dietary fibre and 7% fat. Different heat treatments, except for fluidized bed drying, inactivated the lipase activity in germ completely. On the other hand, various heat treatments inactivated lipoxygenase activity to varying extents (78–92%). Extent of gelatinisation, as assessed in electron micrographs was least in steamed and fluidized bed dried samples, while steamed and oven-dried germ and drum dried germ samples exhibited greater extent of gelatinisation. The extent of gelatinisation seemed to be more in drum-dried sample as no intact starch granule was observed. Electrophoretic pattern and sub-unit composition of germ samples remained similar, irrespective of their nature of treatment. Raw germ showed a gelatinisation temperature of 67.9 °C as measured in visco-amylograph and increased to 80.3–88.3 °C for differently treated germ samples, except for drum-dried sample. Differently heated germ samples, depending on their extent of pre-gelatinisation, gave significantly lower peak viscosity (221–268 BU) and break down values (0–9 BU).     

Mathematical Modeling and Experimental Study on Thin-Layer Vacuum Drying of Ginger (Zingiber Officinale R.) Slices

The vacuum-drying characteristics of ginger (Zingiber officinale R.) slices were investigated. Drying experiments were carried out at a constant chamber pressure of 8 kPa, and at four different drying temperatures (40 °C, 50 °C, 60 °C, and 65 °C).The effects of drying temperature on the drying rate and moisture ratio of the ginger samples were evaluated. Efficient model for describing the vacuum-drying process was chosen by fitting five commonly used drying models and a suggested polynomial was fitted to the experimental data. The effective moisture diffusivity and activation energy were calculated using an infinite series solution of Fick’s diffusion equation. The results showed that increasing drying temperature accelerated the vacuum-drying process. All drying experiments had only falling rate period. The goodness of fit tests indicated that the proposed two-term exponential model gave the best fit to experimental results among the five tested drying models. The average effective diffusivity values varied from 1.859 × 10⁻⁸ to 4.777 × 10⁻⁸ m²/s over the temperature range. The temperature dependence of the effective moisture diffusivity for the vacuum drying of the ginger samples was satisfactorily described by an Arrhenius-type relationship with activation energy value of 35.675 kJ/mol within 40–65 °C temperature range.     

Principal component analysis to study the effect of temperature fluctuations during storage of frozen potato

 The effects of temperature fluctuation ranges, number of fluctuations carried out, and packaging during frozen storage on the texture of potato tissue in terms of compression, shear, and tension rheological parameters were assessed through data generated according to a factorial design using principal component analysis (PCA). Five ranges of fluctuation (–24  °C to –18  °C, –18  °C to –12  °C, –12  °C to –6  °C, –24  °C to –12  °C and –18  °C to –6  °C) applied 2, 4, 8, 16, 24, and up to 32 times on unpacked and pre-packed frozen potatoes, were considered. The controls were unpacked and prepacked frozen tissues thawed immediately without undergoing any fluctuation. In addition, several geometrical, technological, and chemical parameters were determined. PCA showed that maximum shear force, F_s was the best rheological parameter for differentiation of the structural damage and softening occurring in the tissue at each treatment, which was closely related to its duration, TT _d . PCA did not permit complete discrimination between the five fluctuation ranges, but it clearly separated samples subjected to –18  °C/–6   °C from those subjected to –24  °C/–18  °C. Frozen samples undergoing up to four fluctuations formed a separate cluster from those undergoing a higher number. Analysis also clearly separated unpacked from pre-packed samples in response to slower freezing rates reached in the latter. Received: 17 December 1999     

Effects of high pressure treatment on physicochemical characteristics of fresh sea bass (Dicentrarchus labrax)

The effects of high pressure (HP) treatment (pressure: 220–250–330 MPA; holding time: 5 and 10 min; temperature: 3, 7, 15 and 25°C) on physicochemical characteristics (colour, thiobarbituric acid, trimethylamine nitrogen values) of fresh sea bass fillets were investigated. HP-treated sea bass fillets had higher lightness (Hunter L*) values than untreated sea bass fillets; the magnitude of changes increased with treatment pressure. HP-induced changes in colour generally imparted a cooked sample. The TBA value of HP treated sea bass samples (except 220–330 MPa, 3°C for 5 min) were found to be insignificant (P > 0.05) or significantly (P < 0.05) lower than the untreated samples. TMA-N content of HP treated at 220–250–330 MPa, 3–7–25°C for 10 min sea bass samples were found to insignificant according to the untreated samples. The results obtained from this study showed that the quality of high pressure treated sea bass is best preserved at 220 MPa, 25°C for 5 min.     

Effect of temperature fluctuations during frozen storage on the quality of potato tissue (cv. Monalisa)

 Results are presented on the effect of different ranges of temperature fluctuation (–24 to –18°C, –18 to –12°C, –12 to –6°C, –24 to –12°C and –18 to –6°C) on the compression, shear and tension parameters of packed and unpacked frozen potato tissue. The initial temperature, duration and number (2, 4, 8, 16, 24 and 32) of fluctuations were varied. The highest parameter values occurred in samples subjected to fluctuations between –24°C and –18°C, and the lowest values in the range –18 to –6°C. The mechanical strength of the frozen tissue decreased with an increase in the number of fluctuations and in most cases was lower in the packed samples. Moisture loss was greatest in the –18 to –6°C range for pre-packed samples. Changes in the maximum compression force, as a measure mechanical damage, showed the greatest level of significance. Received: 17 June 1997     

Effect of temperature fluctuations during frozen storage on the quality of potato tissue (cv. Monalisa)

 Results are presented on the effect of different ranges of temperature fluctuation (–24 to –18°C, –18 to –12°C, –12 to –6°C, –24 to –12°C and –18 to –6°C) on the compression, shear and tension parameters of packed and unpacked frozen potato tissue. The initial temperature, duration and number (2, 4, 8, 16, 24 and 32) of fluctuations were varied. The highest parameter values occurred in samples subjected to fluctuations between –24°C and –18°C, and the lowest values in the range –18 to –6°C. The mechanical strength of the frozen tissue decreased with an increase in the number of fluctuations and in most cases was lower in the packed samples. Moisture loss was greatest in the –18 to –6°C range for pre-packed samples. Changes in the maximum compression force, as a measure mechanical damage, showed the greatest level of significance. Received: 17 June 1997