Effect of abrasive pre‐treatment on drying rate of grape berries and raisin quality

Abstract

Grape (Vitis vinifera L.) is a delicious fruit with a rich source of different phytochemicals, antioxidants, and it has many health benefits (Yang et al., 2009). The total area under cultivation of grape vine in the world is 7.4 Mha with a production of 77.8 million tons of grapes (OIV, 2019). China, Italy, the United States, Spain, and France are the major grape-producing countries in the world. India ranks at seventh position in the world and produced 2.9 million tonnes of grapes in 2018. Grapes are either consumed for table purpose or processed into products such as wine, raisin, jam, juice, jelly, and other by-products (Venkitasamy et al., 2019). In countries like the United States, Spain, France, Australia, and Argentina, 65%-95% of total grape production is used for winemaking whereas China, India, Iran, Uzbekistan, and Egypt have more consumption of grapes as table purpose (OIV, 2019). The per cent production of grapes for raisin is lesser compared to table grapes and winemaking among the major grape growing countries in the world. In India, about 5.9% of grape is used for raisin production with a total production of 23,500 metric tonnes of raisins (OIV, 2019). Raisin is the dried product of

Novel alternative pretreatment approaches for production of quality raisins from grapes: Opportunities and future prospects

“…Different chemicals have been tried for this purpose and presently alkali based chemicals namely, sodium hydroxide (NaOH) or potassium carbonate (K 2 CO 3 ) and oil emulsion (ethyl oleate) are being commercially used by the raisin producers (Ashtiani et al, 2020; Carranza‐Concha et al, 2012; Doymaz, 2006; Doymaz & Pala, 2002; Patidar et al, 2021; Wang et al, 2017). Recently, some alternatives to chemical pretreatment such as surface abrasion (Adiletta et al, 2016; Di Matteo et al, 2000; Pawar, Giri, & Sharma, 2021; Pawar, Giri, Sharma, & Kotwaliwale, 2021; Senadeera et al, 2014) thermal and nonthermal techniques (Dev et al, 2008; Khiari et al, 2019; Salengke & Sastry, 2005) are being explored by the researchers.…”

“…Among the alkali substances, potassium carbonate has been proven to be effective and has been studied at a concentration of 1%–5% (Telis et al, 2006). In general, 1.5% of potassium carbonate and 1%–2% of ethyl oleate were recommended for better grape drying with good quality raisins (Pangavhane et al, 1999; Pawar, Giri, Sharma, & Kotwaliwale, 2021; Sharma & Adsule, 2007; Telis et al, 2006). Other chemicals such as sulfur, potassium metabisulphite (KMS), and methyl oleate (Bolin & Stafford, 1980) have also been studied for enhancing the drying rate of grapes and maintaining the color of the dried product (Doymaz, 2006).…”

“…The major advantage of this treatment is that no chemicals are required and the process produces safe raisins. The drying also occurred at a faster rate (Adiletta et al, 2016; Pawar, Giri, Sharma, & Kotwaliwale, 2021; Senadeera et al, 2014) compared to untreated and chemically treated grapes and thus saves the total processing time.…”

“…The abrasive surface should be mild enough that only a superficial layer of wax is removed without peeling, otherwise, it will cause stickiness in the prepared raisin samples. So far, most of the researchers have developed a laboratory‐scale abrasive pretreatment system (Adiletta et al, 2016; Di Matteo et al, 2000; Senadeera et al, 2014; Thakur et al, 2010), whereas Pawar, Giri, Sharma, and Kotwaliwale (2021) have developed an industrial scale abrasive pretreatment system made of food grade stainless material.…”

“…However, this waxy layer becomes the crucial hurdle in the natural drying of grapes. Therefore, removal or weakening of the waxy layer is the main target of different pretreatments used in grape drying (Adiletta et al, 2016; Bai et al, 2013; Pawar, Giri, Sharma, & Kotwaliwale, 2021). Chemical pretreatment is most common and commercially used by all raisin producers (Patidar et al, 2021).…”