Effect of Free or Encapsulated Recombinant Aminopeptidase of Lactobacillus rhamnosus S93 on Acceleration of Cheddar Cheese Ripening

The use of recombinant aminopeptidase (PepN) from Lactobacillus rhamnosus S93 in free or encapsulated form was investigated to shorten the duration of Cheddar cheese ripening. Proteolysis was determined by measuring the soluble nitrogen as phosphotungstic acid (PTA-N) derivatives and free amino acids (FAA) over a 6-month period. The experimental cheeses received higher scores for sensory properties than the control cheese. The amounts of PTA-N and total FAA in the cheese with the encapsulated enzyme after 2 months of ripening were close to those of the control cheese after 6 months, suggesting the acceleration in proteolysis by about 4 months.     

Gaussian orthogonal matrix transform approach for PAPR reduction of optical OFDM signals

Optical orthogonal frequency division multiplexing (O-OFDM) has been widely adopted as a high-speed data transmission technique in visible light communication systems. This technique usually suffers from high peak-to-average-power ratio (PAPR). In this paper, a new PAPR reduction technique is proposed for O-OFDM signals. At the transmitter, a matrix transformation with the Gaussian elements is applied to the time-domain O-OFDM signal and at the receiver, the inverse matrix is used to recover the original signal. We show that the Gaussian orthogonal matrices can reconstruct the original signals without degrading the bit error rate (BER) performance. Gram-Schmidt technique is used to orthogonalize the Gaussian matrices. Computer simulations are conducted for 16-QAM baseband modulated symbols and about 3 dB PAPR reduction gain is achieved by the proposed approach compared with conventional O-OFDM.     

Performance improvement of OFDM systems using compressive sensing with group LASSO signal reconstruction algorithm

Wireless Networks - Orthogonal frequency division multiplexing (OFDM) has been investigated for the high-speed transmission of data in radio frequency and optical wireless communications. The OFDM...     

Distribution agnostic Bayesian compressive sensing with incremental support estimation

In most compressive sensing algorithms, such as L1-optimization and greedy family techniques, the only a priori information utilized in the reconstruction procedure is the sparsity information. Meanwhile, there exists another family of techniques based on the Bayesian strategy, which considers comprehensive a priori statistical knowledge of the sparse data. This feature resulted in more increased attention to this category of algorithms. One member of the Bayesian-based family of compressive sensing reconstruction algorithms is the support Agnostic Bayesian Matching Pursuit, which is agnostic to support distribution.However, its high computation complexity in determining the set of dominant supports makes this algorithm unfeasible for practical applications such as wireless sensor networks (WSNs). Due to the special conditions of WSNs, consists of limited-power sensors, developed algorithms for them must have the least possible amount of computations. Given this, in this paper, we propose a Bayesian-based method with incremental support detection for distributed sparse signal recovery, which considerably reduces computational complexity. In the proposed method, in a network of sensors, sparse signal reconstruction from noisy measurements is done distributively and in the form of incremental cooperation. So, the number of required computations will be significantly reduced, which will result in a fast approach. The computer simulations show the superior performance of the proposed incremental Bayesian recovery method.

     

Effect of free and encapsulated recombinant aminopeptidase on proteolytic indices and sensory characteristics of Cheddar cheese

The recombinant aminopeptidase of Lactobacillus rhamnosus S93 in free or encapsulated form was used in production of Cheddar cheese. The effects of these enzymes on the proteolytic indices as well as sensory characteristics have been investigated during Cheddar cheese ripening. An extrusion method was used to encapsulate the enzyme in alginate beads coated with chitosan. The free or encapsulated aminopeptidase were added at the renneting or salting stage at three different concentrations (50, 500, 2000 units per 18 L of milk). Indices of secondary proteolysis were enhanced by increasing the enzyme concentration. Cheeses with the highest concentration of the encapsulated enzyme had significantly higher concentrations of soluble nitrogen in phosphotungstic acid and total free amino acids and received the highest mean scores for the sensory characteristics.     

Volatile Flavor Profile of Saskatchewan Grown Pulses as Affected by Different Thermal Processing Treatments

The objective of this study was to identify and quantify the volatile flavor composition of selected Saskatchewan grown pulses including navy beans, red kidney beans, green lentils, and yellow peas, and to determine the flavor changes induced by thermal processing. Flavor profile of roasted flours, ground roasted seeds, pre-cooked seeds, pre-cooked slurries, pre-cooked–freeze-dried, and pre-cooked–spray-dried flours was studied using headspace solid-phase microextraction gas chromatography/mass spectrometry. The highest total area count (p < 0.05) was found in navy bean and the lowest in red kidney bean. 3-Hexanol was the most abundant volatile flavor compound. Pre-cooking significantly reduced (p < 0.05) volatile compounds total area count by 61.75%, except for the red kidney bean and yellow pea, whereas roasting significantly increased (p < 0.05) total area count for navy bean and red kidney bean. Major differences observed in relative peak area for the same chemical family showed that volatile flavor compounds of pulses were significantly affected by type and processing conditions. Basic knowledge of the volatile profiles of pulses and the flavor changes occurred following different types of thermal processing, could ensure better quality control of raw materials and help product developers meet flavor-delivery challenges. The relevant information may also be of interest to relevant industries targeting specific pulse-based food product development.     

Volatile flavour profile changes in selected field pea cultivars as affected by crop year and processing

The objectives of this study were to evaluate the effect of cultivar, crop year and processing (dry milling, cooking and dehulling) on volatile flavour compounds of field peas using an optimised headspace-solid phase microextraction gas chromatography–mass spectrometry method. Significant differences in area counts of volatile compounds were observed between the different cultivars as well as in area counts of volatile compounds of each cultivar grown in different crop years. Results showed significant reduction in total area counts (TAC) of volatile compounds after cooking and dehulling the seeds. Major differences between whole seeds, cooked and dehulled seeds were found in aldehydes, alcohols, and ketones. Cooked–dehulled peas had the least TAC (7.83E±05) of the volatile compounds compared to the milled-whole peas (6.36E±06), cooked-whole peas (2.00E±06) and milled–dehulled peas (4.33E±06). The results suggest that volatile flavour compounds of different field peas were affected by the cultivar, crop year as well as processing conditions.     

Changes in volatile flavour compounds in field pea cultivars as affected by storage conditions

The impact of storage conditions on volatile flavour profile of field pea cultivars was evaluated. Seeds were kept at 4 °C, room temperature (approximately 22 °C) and 37 °C for 12 months. Headspace solid‐phase microextraction gas chromatography–mass spectrometry was used for extraction and identification of volatile flavour compounds (VFCs). Significant (P < 0.01) differences in the concentration of VFCs were observed during storage. All cultivars kept at 22 and 37 °C had higher mean value of aldehydes compared to those kept at 4 °C. Alcohols, hydrocarbons, ketones, terpenes and esters were higher in samples stored at 4 °C compared to those at higher temperatures. 1‐Hexanol, hexanal, styrene, 2‐butanone, dimethyl sulphide, 3‐carene, ethyl acetate and 2, 3‐diethyl‐5‐methyl pyrazine were the most abundant compounds found in peas. Results from this study could be useful in identifying improved conditions of storage to enhance flavour properties of peas.     

Proteolysis development in enzyme-modified Cheddar cheese using natural and recombinant enzymes of Lactobacillus rhamnosus S93

Proteolysis in enzyme-modified cheese was investigated with natural crude enzyme or recombinant aminopeptidase, both derived from Lactobacillus rhamnosus S93 in the presence of a commercial proteinase, Neutrase. For production of enzyme-modified cheeses, a cheese slurry was produced and pre-incubated with Neutrase. Natural enzyme or recombinant aminopeptidase (50 units 200 g⁻¹ slurry) was added alone or in combination to the cheese slurries, which were then incubated anaerobically under vacuum at 37 °C for 1, 3 and 6 d. The greatest levels of phosphotungstic acid soluble nitrogen and free amino acids were observed in the enzyme-modified cheese containing natural enzyme followed by the one treated with a combination of the natural enzyme and recombinant aminopeptidase. The enzyme-modified cheese containing the recombinant aminopeptidase alone resulted in the complete disappearance of proline after 1 d of maturation time.