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Volume 13, Issue 2, 2024

Online ISSN: 2182-1054

Volume 13 , Issue 2, (2024)

Published: 18.10.2024.

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18.10.2017.

Original scientific paper

The interaction effect of mixing starter cultures on homemade natural yogurt’s pH and viscosity

Dairy yogurts are common food products consumed by people all over the world. Due to the simple process, many people have made their own natural yogurt at home. The fermentation due to the starter culture causes the textural properties of dairy yogurt. However, the literature is surprisingly scarce on the topic of starter culture interactions in the development of textural properties of dairy yogurt. This study investigated the interaction effect of three common starter cultures, Lactobacillus acidophilus, Lactobacillus bulgaricus and Streptococcus thermophiles, on the viscosity of homemade yogurt. Using Design Expert software, a 10-run mixture model experiment was designed to examine the textural properties developed by single or multiple inoculation of these starter cultures. All yogurt formulations reached the isoelectric point of milk and had pHs in the range 3.97 to 4.32. Yogurt formulations with L. acidophilus and S. thermophilus resulted in viscosities which were similar to commercial yogurt viscosity (1.77 Pa·s), while L. bulgaricus resulted in yogurt with a lower viscosity. Based on the mixture model, L. acidophilus had most influence on the yogurt viscosity, followed by S. thermophilus and L. bulgaricus. In conclusion, L. acidophilus can be used as a single starter culture or combined with other starter cultures to develop high viscosity homemade yogurt. A Combination of S. thermophilus and L. acidphilus can also be used to develop high viscosity yogurts. However, L. bulgaricus should not be inoculated alone or become a dominant ratio in multiple starter culture inoculation as it will decrease the overall homemade yogurt viscosity.

Hadi A. Dahlan, Norrakiah A. Sani

18.04.2017.

Original scientific paper

Extrusion cooking technology: Principal mechanism and effect on direct expanded snacks – An overview

The snack industry is one of the fastest growing food sectors and is an important contributor within the global convenience food market. Nowadays snacks and convenience foods are also consumed regularly in India. Properly designed convenience foods can make an important contribution to nutrition in societies where social changes are altering traditional patterns of food preparation. Extrusion cooking as a popular means of preparing snack foods based on cereals and plant protein foodstuff has elicited considerable interest and attention over the past 30 years. Several studies on the extrusion of cereals and pulses, using various proportions, have been conducted because blends of cereals and pulses produce protein enriched products. Special importance is placed on the physicochemical and chemical modifications of protein, starch and dietary fibre. Extruded products can be categorized for a particular application based on their functional properties such as water absorption and water solubility index, expansion ratio, bulk density and viscosity of the dough. Therefore, the literature was reviewed for effect of extrusion processing on product parameters, and nutritional and anti-nutritional properties of extruded products.

AJITA TIWARI, Jha S. K.

18.04.2017.

Original scientific paper

Vacuum-assisted microwave drying characteristics of green bell pepper

Chopped green bell pepper pieces were blanched (95 °C, 5 min) and chemically pretreated (1% potassium metabisulphite solution, 25 min at room temperature) before drying in hot air dryer (HAD) at various temperature ranges (60 – 80 °C). Three vacuum levels (200, 400, 600 mm Hg) and microwave power levels (100, 200, 300 W) were also used to dry green bell pepper samples in a vacuum-assisted microwave (VAM) (2.45 GHz, 0.8 kW) dryer. VAM drying methods offered a maximum reduction by four to five times in drying time as compared to that in HAD. The logarithmic model was found to have the best fit based on high R2 and small values of reduced χ 2 and RMSE. VAM method has higher values for effective moisture diffusivity (Deff ) and lower values for activation energy (Ea), in comparison to the HAD method.

Vivek Kumar, Shanker L. Shrivastava

18.04.2017.

Original scientific paper

Texture analysis of blanched vegetables using high- and low-speed measuring methods

Quality reductions of raw and cooked vegetables are caused by forces generated during industrial high-speed manufacturing. However, the transferability of low-speed texture measurement methods to high speed processes is limited. Therefore, analyses with a low-speed uniaxial compression test (breaking strength σ, breaking strain ε) and a high-speed pendulum test (relative fracture height ∆h) at different speeds (3.6, 4.4, 5.3 m s−1 ) were carried out. Textural values for potatoes, carrots and celeriacs (0 to 25 min cooking time) were recorded to compare the two measurement methods. Furthermore, whether the increase of textural values of blanched vegetables measured with low-speed methods, was also observable with high-speed methods, was also investigated. Low to medium rank correlation coefficients (rS < 0.659) between parameters of the two methods were calculated. In contrast to σ and ε, ∆h-values indicate a distinct initial increase as well as textural maxima between 5.0 to 12.5 min cooking time for all tested potato and carrot varieties. On the other hand, most celeriac samples did not exhibit an increase in texture with respect to cooking time. Therefore, a textural analysis at high speeds is necessary for the prediction of textural characteristics of blanched vegetables during high-speed processing in order to reduce quality degradation.

Christian Schmitt, Thomas Friedl, Nadine Mattes, Uwe Grupa, Oliver Hensel

18.04.2017.

Original scientific paper

Optimization of microwave vacuum drying parameters for germinated lentils based on starch digestibility, antioxidant activity and total phenolic content

The aim of this study was to optimize the processing parameters of pulse mode microwave-vacuum drying of germinated green and red lentils (CDC Greenland and CDC Maxim) and investigate the changes in their total phenolic content (TPC), total antioxidant activity (TAA) and In-vitro starch digestibility (SD). The lentils were germinated for 5 days and dried by a pulse mode microwavevacuum method, using 2 s to 8 s out of 10 s pulsed mode at 2000W microwave power and varying the vacuum pressure level between 15 and 45 kPa. In-vitro starch digestibility increased significantly with increased microwave power level. The TPC and TAA appeared to vary distinctively in the two varieties of selected lentils. Vacuum pressure levels did not significantly (p>0.05) affect any responses. Green lentils could be dried at 8 s microwave power and 45 kPa vacuum pressure and red lentils could be dried at 5.5 s microwave power and 42.19 kPa vacuum pressure. The microwave-vacuum drying showed great potential for the drying of germinated lentils. 

Robbarts Nongmaithem, Venkatesh Meda

01.12.2016.

Professional paper

Effect of Grewia venusta FRESEN mucilage on the proximate composition, physical and sensory properties of bread produced from wheat and cassava composite flours

Wheat and cassava composite breads are generally associated with volume and textural defects in contrast with the traditional wheat based variants. Efforts to mitigate this challenge through use of synthetic additives have been unsuccessful owing to safety concerns. The objective of this study was to explore Grewia venusta mucilage as a potential natural additive in wheat-cassava composite bread production. Sweet cassava flour was used to replace wheat flour at 100: 0 (control), 90:10, 80:20 and 70:30% ratios in bread making. Aqueous extract of G. venusta stem bark was oven dried (50±3 oC), milled and added at 0, 1.0 and 2.0% (w/w) to the flour mixtures. These, along with other conventional inputs were mixed, and used to produce bread. Proximate compositions, physical and sensory properties of the bread loaves were evaluated. Cassava flour inclusion resulted in significant (P≤0.05) decrease in the protein content of the control from 18.1% to 12.1% (90:10%), 11.5% (80:20%) and 9.9% (70:30%). Addition of mucilage marginally increased the protein and dietary fibre contents of the loaves. Loaves containing 1-2% mucilage were more regular in shape with smoother crust than those without mucilage. Cassava flour addition at 10%, 20% and 30% decreased loaf height from 6.0 cm to 5.8 cm, 5.7 cm and 5.5 cm, as well as loaf volume from 815.5 cm3 to 783.1 cm3, 776.8 cm3 and 744.5 cm3, respectively. Mucilage inclusion resulted in increased heights and volumes of the loaves and reduced weights of loaf fragments upon slicing. The mucilage significantly improved the texture of the bread loaves. 

Arubi P. Alobo, Gibson L. Arueya

01.12.2016.

Professional paper

Effect of tuna skin gelatin-based coating enriched with seaweed extracts on the quality of tuna fillets during storage at 4 °C

Nowadays, consumers demand high quality food products with an extended shelf-life without chemical additives. Edible coatings (EC) containing natural compounds are a promising preservation technology for raw seafood without compromising fresh-like appeal and nutritional content.The aim of this work was to evaluate the effect of Thunnus obesus skin gelatin-based EC containing Codium spp. or Fucus vesiculosus extracts on raw tuna preservation. Three gelatin-based EC (gelatin (5 %) + glycerol (25 %); gelatin (5 %) + Codium spp. (1 %) + glycerol (25 %); gelatin (5 %) + Fucus vesiculosus (1 %) + glycerol (25 %)) were applied directly on the surface of tuna fillets. Functional properties of gelatin and gelatin-based EC containing seaweed extracts were also studied. The gelatin was extracted by an acid-swelling process in the presence/absence of pepsin, followed by subsequent heating/refrigeration, after a pre-treatment with NaOH. The type of acid, temperature and concentration of NaOH greatly influence the process yield. The higher extraction yield was achieved using acetic acid in the presence of pepsin by subsequent refrigeration, especially when skins were previously treated with NaOH (0.2 M). Tuna quality was assessed over 12 days of storage at 4 ± 1 °C in terms of chemical and microbial indices. Results showed that tuna skin gelatin-based EC avoids tuna deterioration. Microbial growth, assessed by total viable counts, and total volatile basic nitrogen were maintained below the maximum limits recommended, contrarily to the control. Additionally, the use of EC increased the stability of red colour during storage. 

Milene Vala, Ana Augusto, André Horta, Susana Mendes, Maria M. Gil

01.12.2016.

Professional paper

Influences of physicochemical stresses on injury and inactivation behaviour of Listeria innocua

Many minimally processed foods depend on a combination of inhibitory factors to reduce the hazard of foodborne illness. Therefore, inactivation of Listeria innocua was studied according to a 24 factorial experiment designed to draw conclusions about temperature (52.5 °C and 65.0 °C), pH (4.5 and 7.5), water activity (aw=0.95 and 0.99) and solute type (NaCl and glycerol) effects. Three different recovery media were used to assess injured cells. Survival data were fitted with a Gompertz-based model and kinetic parameters (shoulder, maximum inactivation rate – kmax, and tail) were estimated. Results showed that shoulder was affected by temperature, pH and combined effects; kmax was influenced by all factors and their combinations; and tail was affected by aw, temperature and aw/pH combination. Results demonstrated the potential occurrence of microbial cross-protection survival techniques between the various stresses, e.g. heat and osmolarity. Indeed, this work clearly established that, to avoid hazards, Listeria inactivation must be evaluated with a maximum of environmental factors that undergo alterations. Only thus, appropriate food preservation treatments can be developed and consequently, the safety of food products can be assured.

Fátima A. Miller, Bárbara Ramos, Maria M. Gil, Teresa R.S. Brandão, Paula Teixeira, Cristina L.M. Silva

18.10.2016.

Original scientific paper

Solubility of Stevioside and Rebaudioside A in water, ethanol and their binary mixtures

In order to investigate the solubility of Stevioside and Rebaudioside A in different solvents (ethanol, water, ethanol:water 30:70 and ethanol:water 70:30), supersaturated solutions of pre-crystalized steviol glycosides were maintained at different temperatures (from 5 °C to 50 °C) to reach equilibrium. Under these conditions significant differences were found in the extent of solubility. Rebaudioside A was poorly soluble in ethanol and water, and Stevioside was poorly soluble in water. Solvent mixtures more effectively promoted solubilisation, and a significant effect of temperature on solubility was observed. The two steviol glycosides showed higher solubilities and this behavior was promoted by the presence of the other sweetener. The polarity indices of the solvents were determined, and helped to explain the observed behavior. Several solute-solvent and solute-solute interactions can occur, along with the incidence of a strong affinity between solvents. The obtained results are in accordance with technological applications of ethanol, water and their binary mixtures for Stevioside and Rebaudioside A separations.

LILIANA CELAYA, Eugenio Kolb, Nicolas Kolb

18.04.2016.

Original scientific paper

Innovation and knowledge transference in a cluster user-driven innovation perspective – the Inovcluster experience

Our purpose with this article is to show the importance of assessing trends and promoting innovation in a real business context, through a cluster ecosystem, mainly composed of micro-enterprises in the agro-industrial Portuguese sector. As many studies show, Inovcluster (which has 158 associates, from which 120 are enterprises) is also a geographic region cluster, which improves innovation performance of businesses seeking to gain competitiveness and ability to improve their exportations in the agro-industrial Portuguese sector. The role of the cluster is fundamental to creating a model for knowledge transfer of innovation capacity, interconnecting its institutional, scientific and business associates. This model has to be adapted to the sector and enterprise characteristics, relying in an interconnecting structure which is more or less decentralized according to the mentioned features. Here we present an experience and case study of the Inovcluster ecosystem and its trends and innovation transfer to business value creation, contextualized within the regional strategy for smart specialization. We have shown how, through the establishment of an Inovcluster network, it is possible to integrate the contribution of different research and academic centres, channelled to assist micro-enterprises by innovating within a geographical constraint.

Teresa Paiva, Claudia Domingues, Luıs Pinto de Andrade

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