INTRODUCTION
In recent years, consumers have become more and more health conscious and this has become one of the leading motivation of manufacturers and researchers The food industry is also embracing this tendency by developing products with health commitments in mind Accordingly, traditional products are also improved to enhance nutritional value as well as help it be labeled as "healthy food"
Pasta is a traditional product with global popularity based on low cost, long shelf life and high global consumption [1] They are usually made from durum wheat semolina and water, ensuring enough energy for a meal [2] Pasta is also classified as a
“healthy food” with a low glycemic index [3] Huang et al (2017) have shown that glycemic levels in pasta are significantly lower than in white rice [4] Pasta has also been demonstrated to carry no risk of diabetes with long-term consumption and can significantly reduce the risk of stroke as well as the risk of atherosclerosis [5] However, pasta is quite poor in fiber They have been recorded to contain only about 8.46g fiber compared to 11.60g protein and 75.20g carbohydrate per 100g pasta [6] Therefore, the study on the addition of different sources of dietary fiber to pasta has become a trend for a long time Baiano et al (2006) used whole wheat flour to replace refined flour, resulting in a threefold increase in total dietary fiber (3.21/ 100 g - 9.88 /100g) [7] Additionally, Lu et al (2018) used white button mushrooms, shiitake mushrooms and porcini mushrooms to enrich the pasta nutrients [8] The results showed that at only 5% substitution, the dietary fiber content increased significantly, from 3.17/ 100 g to 6.04/
100 g [8] Vimercati et al (2021) also incorporated spinach as a supplement to pasta and also noted a significant increase in total fiber content [9]
Pennywort (Centella asiatica L.), which is a potential medicinal plant in the
Apiaceae family, is traditionally used in wound and antibacterial treatment in Asia,
South Africa and Eastern Europe [10] Besides, pennywort is also consumed as fresh vegetable and juice in many countries The production of pennywort juice at industrial scale results in a large amount of pennywort pomace, which is high in dietary fiber and phenolics including quercetin, kaempherol, catechin, rutin, apigenin and naringin [10]
Although the use of this residue in the formulation of food products has not been reported yet, pennywort by-product can be considered as a source of dietary fiber as well as antioxidants for food enrichment [11]
Despite the fact that the addition of fiber ingredients from plant-based by- products to pasta recipe improves the dietary fiber content, the decreased gluten content can have negative effects on the cooking quality, textural properties, and overall acceptability of pasta [12] Thus, this study aimed to investigate the effects of supplementation ratio of pennywort pomace powder (PPP) as well as the influences of two potential techniques namely transglutaminase (TG) and tyrosinase (TYR) treatment on the proximate composition, cooking quality, textural profile, and overall acceptability of the product
LITERATURE REVIEW
Diatery fiber
Fiber is defined as plant-based components that are not digested in the small intestine and can be fermented by colon-resident bacteria depending on the type of fiber Fiber is composed of non-starchy carbohydrates and complex lignin [13] Plant cell walls are the major component (more than 95%) of dietary fibre [14] Dietary fiber consists of cell-wall polysaccharides that are typical of the cell walls of many fibers, being composed of pectic polysaccharides, hemicelluloses, and cellulose [15]
There are two types of fiber classified based on solubility, including water-soluble fiber and water-insoluble fiber The structural compositions of the two types of fiber are described in Table 2.1
Table 2.1 Different composition of insoluble and soluble fiber [16]
Insoluble dietary fibers Soluble dietary fibers
Non-starch polysaccharides (NSP) Psyllium
Soluble fibers are transported directly to the colon, where they are fermented by the colon's microflora and produced energy to feed the microflora In most cases, fiber when dissolved in water will form a viscous gel due to structural components such as pectin, galactomannan, and glucomannan They increase gastrointestinal transit time, slow gastric emptying and glucose absorption leading to prolonged satiety [17] In contrast, insoluble fiber will not be fermented during any stage of the digestive process [16] It will be excreted directly in the faeces and at the same time reduce intestinal transit time Soluble fiber is commonly found in legumes, barley, oat bran, and some
4 fruits and vegetables while insoluble fiber is found in foods like wheat bran, vegetables and whole grains [16].
Pennywort
Pennywort (Centella asiatica L.) comes from the family Apiaceae, usually known by the common name pennywort or Centella asiatica L It grows in the tropical regions of Asia, Oceania, Africa and America [18]
Pennywort is currently popular in Southeast Asia countries and some West Asia countries such as Sri Lanka and India It is well-known as a beneficial plant for health, especially for the skin thanks to numerous nutrients such as flavonoids, beta-carotene, steroids, saponins that help protect the skin from the development of free radicals and slows down the aging process [11, 19]
Figure 2.1 Leafs (A), leafs and flowers (B) and the whole pennywort plant (C)
2.2.2 Proximate composition and antioxidant activity of pennywort
2.2.2.1 Proximate composition Table 2.2 Proximate composition of pennywort
Composition Hashim (2011) [20] Joshi và Chaturvedi
There are some differences between the proximate composition of pennywort in Table 2.2 But in general, pennywort has low content of essential nutrients such as protein (2.4%), carbohydrates (6.7%) and fat (0.2%) In addition, pennywort has a high moisture content (84-87%) and also provides a significant amount of dietary fiber It also has high level of potassium and calcium, which provide many health benefits such as reducing stroke, strengthening bones, helping to reduce the risk of heart disease [23]
Table 2.3 Vitamin content of pennywort
In general, pennywort is also rich in vitamins such as vitamin C (48.5 mg/ 100 g), B1 (0.09 mg/ 100 g), B2 (0.19 mg / 100 g), niacin (0.1 mg/ 100 g), carotene (2649 μg/
Triterpene compounds or terpenoids are the main bioactive components that promote the antioxidant properties of pennywort [24] Studies have shown that pennywort extract contains 4 triterpenic components namely asiatic acid (0.55 ± 0.89 mg/ mL), madecassic acid (0.55 ± 2.29 mg/ mL), asiaticoside (1.97 ± 2.65 mg/ mL) and madecassoside (3.10 ± 4.58 mg/mL) [25]
The change in the content of triterpene compounds depends on the ripening stages of pennywort At these ripening stages, pennywort had no significant difference in
7 asiatic acid content However, the levels of madecassic acid, asiaticoside and madecassoside were different depending on the timing of these ripening stages [26]
Pennywort is reported to contain flavonoids including 3-glucosylquercetin, 3- glucosylkaemferol and 7-glucosylkaemferol Since the content of asiatic acid and madecassic acid is quite low, the antioxidant activity of pennywort is mainly contributed by the flavonoid content such as quercetin, kaempherol, catechin, rutin, apigenin and naringin [27] Recently, Suban et al (2008) isolated two novel flavonoids found in pennywort, castilliferol 1 and castillecetin 2 These isolates represent good antioxidant activity with DPPH stock solution [28]
Carotenoids are one of the most important phytonutrients found in pennywort β- carotene is the main carotenoid and a precursor to vitamin A It plays a role in preventing vitamin A deficiency, preventing blindness and strengthening the immune system [29] Chandrika et al (2011) concluded that the β-Carotene content in pennywort leaves is about 8.9 mg/100g dry matter [30]
Lutein is also one of the important carotenoids in pennywort with antioxidant activity It is a major carotenoid constituting the human eye's macular pigment and helps prevent macular degeneration in the elderly [11]
Pennywort contains glycosides such as asiaticoside, madecosside, centelloside, which hydrolyze to form trepene acid, asiatic acid, madegascari acid and centellic acid, all of which are available in free form in pennywort [10]
Pennywort is also reported to contain tannins, inorganic acids, sugars, resins and amino acids, namely aspartic acid, glycine, glutamic acid, α-alanin and phenylalanin [11].
Use of pennywort in value-added products
2.3.1 Use of pennywort in food industry and food preparation
In India, pennywort juice is used as a health tonic, helping to lower blood pressure, relieve central nervous tension and gastrointestinal diseases [31] It is also
8 commonly consumed in India in the form of Brahmi green tea or essential oil, to help replenish the mind and concentration [31]
In Sri Lanka, pennywort is most commonly used as a salad green Pennywort is also cooked in a curry with spices, onions and coconut milk [32] In addition, pennywort is used to make porridge for children to combat nutritional deficiencies in this country [33]
In South Asian countries such as Indonesia, Malaysia, indigenous people often consume pennywort in the form of fresh vegetables to eat raw as salad This salad called
"Ulam" is made from a mixture of pennywort, shrimp, onion and coconut This dish is also rich in micronutrients including vitamins and minerals, which help to combat malnutrition, deficiency of some essential substances for the body and therefore it is often served as an appetizer [31]
2.3.2 Use of pennywort in other fields
In addition to food, other fields that most commonly use Centella asiatica L are cosmetics and pharmaceutical industry In the cosmetic industry, with pennywort’s powerful antioxidant properties, it is an excellent ingredient for firming and stimulating the skin, making it ideal for beauty products [11] The liquid extract from pennywort with gelatin-encapsulated nanoparticles has been tested to inhibit the effects of UV rays on the skin [34]
Pennywort is rich in flavonoids used in scalp care products, where it stimulates the peripheral circulation of the scalp and will promote a healthy scalp condition and prevent hair loss [35]
Additionally, pennywort contains essential oils such as beta-caryophyllene, beta- cymene, trans-beta-farnesene, germacrene-D, alpha-terpineol, limonene and linaloolwere In addition, they contribute to anticancer and various antibacterial activities [36] Pennywort is effective in improving the treatment of minor wounds, hypertrophic wounds as well as burns, psoriasis and scleroderma Their mechanism of action involves promoting fibroblast proliferation and increasing collagen synthesis and intracellular fibronectin content, while improving the tensile strength of newly formed skin as well as inhibiting the inflammatory phase of scarring, hypertrophy and keloid
9 scars [36] In addition to the field of dermatology, it is also used to treat many diseases such as gastric ulcers, gastric mucosal lesions, anxiety disorders [37] and neurological disorders [38] Pennywort has also been found to be beneficial in the treatment of chronic venous insufficiency, mainly by improving microcirculation [39] In Africa, pennywort essential oil is widely used with antibacterial function against gram-positive (Bacillus subtilis and Staphylococcus aureus) and gram-negative (Escherichia coli, Pseudomonas aeruginosa and Shigella sonnei) [40]
Pennywort pomace is a by-product of the pennywort juice industry They have been studied and applied to the animal feed production since they are rich in fiber, essential phytochemicals and unextracted nutrients (aqueous solvents) [41] Although there have been many studies on the application of pennywort, the use of pennywort pomace, especially in food industry, has not been reported yet Moreover, in countries that consume pennywort such as Vietnam and Thailand, pennywort pomace is a by- product that has not been recycled much Therefore, in this study, we considered pennywort pomace as a source of dietary fiber as well as antioxidants for food enrichment.
Application of food residue in the production of fiber-rich pasta
In Italy, the agricultural by-products industry is estimated at €8.5 billion/year [42] These by-products often contain a number of distinct bioactive compounds that will be useful for certain products [43, 44] To be specific, fruit pulp possesses various valuable bioactive compounds such as fiber, carbohydrates, phenolic compounds, polysaccharides, phytochemicals, natural antioxidants and several other health promoting nutrients [45] The idea of recovering these by-products and converting them into complementary ingredients for traditional products is an idea that has been considered for a long time
By-products from grape wine and olive oil production have been studied for their supplementation to pasta with an addition rate of 7% [45] Although this fortification focused on phenolic compounds, the authors noted an increase in total fiber content by approximately 3% and most of the potent antioxidant compounds present in natural
10 grape and olive were found in grape and olive pomace Espinosa-Solis et al (2019) also studied the addition of oat bran by-products to pasta production Although the structural and technological parameters were highly altered due to the high substitution rate (50%), both total fiber content and antioxidant activity of the pasta samples increased significantly [46] Furthermore, Sykut-Domańska et al (2020) studied the addition of copra meal, a by-product from the coconut industry, and coconut meal powder to pasta
In comparison to coconut meal, coconut residue was reported to have a lower fat content while having a higher total fiber content (55.76%) than coconut meal (41.63%) [47] Soybean meal is a by-product of the soybean processing industry It was also added to pasta at the rate of 10 - 50%, resulted in a 50% improvement in total phenolic content and antioxidant activity while the glycemic index of the pasta decreased significantly (from 27.41 ± 0.05 to 12.38 ± 0.01) [48]
In addition, carrot pulp has also been studied as a potential supplement to pasta product since it has good nutritional and structural properties [6] Padalino et al (2019) added tomato peel powder to pasta at a rate of 15% and measured a significant increase in total dietary fiber content As a result, they reported a decrease in carbohydrate intake from 68g/100g to 60g/100g This suggested a significant reduction in the glycemic response of pasta with tomato peel powder [12].
Transglutaminase
Transglutaminase (TG) is an enzyme that creates crosslinks between protein molecules, which catalyze the acyl transfer reaction between the carboxyamide group of the glutamine group (acyl donor) and a variety of major amines (acyl acceptors), including the four amines of lysine residues in some proteins [49] In the absence of an amine substrate, TG catalyzes the deamination of glutamine residues in which water molecules will act as acyl acceptors [50] TG are found in animal tissues, animal blood, and plant tissues, and recently they have also been found in microorganisms [51]
2.5.2 Applications of transglutaminase (TG) preparation in food
TG can restructure meat at temperatures below 10 o C overnight It works best when combined with caseinate; it will make the caseinate viscous and act as a glue to
11 hold the meat texture together Furthermore, the addition of TG and caseinate may enable the production of healthy, low-fat meat by creating cross-links in the microstructure of these products [52]
TG also induces suwari in fish, which is a gelling phenomenon where myofibrillar proteins interact to form a network, thereby contributing to the improvement of the elasticity and stiffness of the fish material [53] It has also been found that TG has the ability to use casein in milk as a substrate to create a heat-stable hard gel in the TG catalyzed reaction and it can be applied to yogurt production [54] Another important application of TG is in soy products, especially tofu In these products, TG can use soy proteins such as 11S and 7S globulins as substrates, in combination with the addition of
Ca 2+ , Mg 2+ and glucono-d-lactone, thereby maintaining the smooth and durable properties of tofu [54]
2.5.3 Effect of transglutaminase on noodles and pasta
TG catalyzes the reaction between amino acids in nooldes and pasta products according to the mechanism of acyl-transfer reactions via 2 steps:
In the first step, the γ-carboxamide group of the peptide is derived from glutamine, an amino acid present in more than 40% of the amino acids in gluten proteins [55] and considered as an acyl donor, interacting with cysteine residues (thiol radicals)
- an amino acid that currently makes up about 2-3% of gluten proteins [56] This reaction form the intermediate, a covalent acyl-enzyme intermediate (called a thioester) and release ammonia [57]
As a second step, this thioester intermediate reacts with a second substrate, primarily the amine group of the Lysine moiety - an amino acid that makes up a very small amount of gluten (