Effect of cultivars, wound healing and storage on sensory quality and chemical components in pre-peeled potatoes
Introduction
In the last decades consumers’ demand for convenient, ready-to-use or ready-to eat food products with a safe and fresh-like quality has increased (Day & Gorris, 1993). Minimally processing techniques, shelf-life and quality aspects of such products are subjects of high relevance for future product development (Ohlsson, 1994; Ahvenainen, 1996).
Raw pre-peeled potatoes form the basis for minimally processed ready-to-cook potatoes. The product is an alternative to pre-cooked vacuum-packed or canned potatoes. Pre-peeled potatoes are peeled, packed in vacuum or modified atmosphere and have a limited shelf-life of 5–7 days at 4–5 °C, due to microbiological, sensory and nutritional deteriorations (Keijbets, 1988; Chassery & Gormley, 1994; Schlimme & Rooney, 1994). The major quality aspect in pre-peeled potatoes is the microbial quality, which, due to safety, has been investigated extensively with respect to effects of chemical preservation agents and modified atmosphere packaging (Keijbets, 1981; O’Beirne & Ballantyne, 1987; Giannuzzi & Zaritzky (1991), Giannuzzi & Zaritzky (1993); Chassery & Gormley, 1994; Giannuzzi, Lombardi, & Zaritzky, 1995). Some of the investigations showed that ascorbic- and citric acid and modified atmosphere packaging could replace the use of sulphur dioxide. Chemical preservation and modified atmosphere packaging were shown to decrease the surface browning of the potatoes and to improve the appearance of the product (O’Beirne & Ballantyne, 1987; Sapers & Miller, 1995). With respect to shelf-life, no attention was addressed to sensory quality of pre-peeled potatoes in terms of aroma and taste quality. Texture is a major quality aspect in pre-peeled potatoes as most pre-peeled potatoes form a compact superficial surface layer (Svensson, 1971; Sapers, Cooke, Heidel, Martin, & Miller, 1997). This surface hardening, or so-called case hardening, of pre-peeled potatoes gives an elastic, hard and crisp surface with varying thickness, which is experienced as a hard and lumpy structure during chewing of the potato and limits the utilization of pre-peeled potatoes. Surface hardening is demonstrated to increase by addition of chemical preservation agents such as ascorbic and citric acid, and sodium acid pyrophosphate (Svensson, 1971; Sapers & Miller, 1995). The surface hardening is also observed to increase by an increased exposure to mechanical stress of the potatoes during handling and peeling in the process line in the industry (Lulai, Glynn, & Orr, 1996; Kaack, Larsen, & Thybo, 2002a). As the surface hardening of pre-peeled potatoes increases during a shelf-life of 5–7 days, it is speculated to be a wound healing process with deposit of suberin in cell layers below the wounded surface (Thomson, Evert, & Kelman, 1995; Kaack, Larsen, & Thybo, 2002b). The suberization will cross-link the cells resulting in strong brick-like tissue structures. However, very little evidence of the reason for surface hardening in raw pre-peeled potatoes is addressed. Furthermore, no attention has been addressed to sensory quality of pre-peeled potatoes in terms of aroma and taste quality.
New approaches in improving the quality and the shelf-life of minimally processed vegetables are important subjects for increasing the sale of raw pre-peeled potatoes in the catering and retail market. This includes optimization of raw material quality, processing conditions (gentle handling, strict hygienic practices, correct packaging technology), distribution and retailing (Ohlsson, 1994; Ahvenainen, 1996).
In order to obtain a better quality of pre-peeled potatoes, this study addresses the effects of agronomic factors as cultivars, wound healing time and long-term storage on sensory quality of pre-peeled potatoes. Furthermore, this study will deal with the chemical variation of the raw potatoes to understand the reason for the sensory quality differences in discolouration, aroma and taste of cooked pre-peeled potatoes.
Section snippets
Cultivation and storage of potatoes
The potato cultivars Berber, Arkula, Marabel, Sava, Folva and Agria were grown in three replicates on a fine sandy soil at Tylstrup Research Station in 1999. The cultivars used represent different maturity classes and are above arranged in order of increasing lateness of maturity. Potatoes were fertilized with 140 kg N, 180 kg K and 11 kg P per ha, planted on April 27, irrigated and managed according to commercial praxis. Date of chemical wine desiccation were adapted to variations in cultivar
Effects of cultivars, wound healing time and storage on quality
The effects of cultivars, wound healing time and storage on sensory attributes and chemical components were determined by analysis of variance. Cultivars had significant influence and contributed with the largest part of the variation in the chemical components in the raw potatoes (Table 1) and the sensory attributes (Table 2) and aroma components in the cooked potatoes. Also, storage had a significant effect on most of the variables. In contrast, duration of wound healing only had a
Conclusion
This study showed that raw material quality and the physiological maturity of the potatoes is a great challenge for the industry in order to optimize the sensory quality and to decrease the presence of quality defects such as surface hardening. The results indicate that some potato cultivars are not suitable for a convenience product as pre-peeled potatoes, either due to surface hardening or negative flavour and taste perception. Choice of cultivar is therefore a very important factor in
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2022, LWTCitation Excerpt :Potatoes skin wounds heal quickly to prevent infections, but the formation of wound-healing tissue leads to surface hardening, which results in a hard and lumpy texture when the product is eaten. Thus, the presence of wound-healing tissue affects the economic value of fresh-cut potatoes (Lulai, 2007; Thybo et al., 2006). Vacuum packaging, which reduces oxygen levels within a package, can inhibit respiration and aerobic metabolism in fruit and vegetables, thus, delaying maturation and senescence (Fang et al., 2018).