豬的好口感(第一章)；甜味

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2011年4月19日

作者: Eugeni Roura 譯者：劉彩紅

動物食物的研究由化學感受器編碼引發，它能夠感覺可用原料的營養價值。食物通過口腔進入胃腸道（GIT），在吞咽前食物在口腔中經過好幾個化學和生理變化反復咀嚼、感受。并饑餓時，化學感受器編碼主要存在于口腔中（主要是嗅覺和味覺），感受食物營養，并觸發或阻止進一步采食。憑借胃腸道-丘腦軸的外圍傳感器決定頭期采食量，并且對于食物的營養和大概用量有一個直接的評價（暫時的）。

     簡單的碳水化合物，例如糖，似乎可以刺激豬甜味感官，增強豬的自由采食。豬日糧中甜味劑的使用是一種普遍實用技術，尤其是對于幼小的動物。在其他的甜味劑中，非碳水化合物高強度甜味劑（HIS）例如糖精（SAC）、索馬甜（THA）、蛇菊苷和新橙皮苷（NHDC）被廣泛地使用。Kennedy 和 Baldwin (1972)研究了蔗糖、葡萄糖、糖精的喜好參數，并建立閾值，蔗糖的參數為0.005-0.01M，葡萄糖為0.01-0.03M。兩種物質豬都表現出一致的偏愛（超過90%）。相反，SAC的結果不同，其喜好參數沒有改善蔗糖，閾值為0.0005=0.1M.此外，SAC的喜好價值沒有超過90%，濃度超過0.1M時被拒食。
      Danilova等（1999）進行了電生理學研究，報告稱豬舌頭對于碳水化合物甜味劑有高度神經元應答，比如存在于單糖或低聚糖之中的果糖，蔗糖或乳糖。在偏好特征測定中，蔗糖在多有碳水化合物測試總表現出最高強度的喜歡，它們的反應與人的糖感覺測試非常相似（Glasser等，2000年）。另一方面，豬對于與人類等同劑量的的HIS沒有應答，例如NHDC，THA，或者SAC（表1）。HIS廣泛使用在豬的飼料中，如SAC和NHDC和/或THA處理組合也沒有表現出更好的應答。
表1  相對于蔗糖（在1摩爾質量基礎上），甜味劑對豬和人的效應（Glasser等，2000）

		相對于蔗糖的作用
		人類	豬(1)
碳水化合物	蔗糖	1.00	1.00
	果糖	0.50	0.50
	乳糖	0.33	0.15
	葡萄糖	0.25	0.13
非碳水化合物	阿斯巴甜	155	< 1.00(2)
	甜蜜素	17.6	< 0.15(2)
	新橙皮苷（二氫查耳酮）	3.6	< 151(2)
	索馬甜	2	< 1.622(2)
	糖精	215	3.34

（1）甜味劑對豬的作用測定建立在偏好雙重選擇偏好測試的基礎上

（2）等同于沒有應答反應的最低劑量測試。精確的作用未被測定。
然而，近年來，甜味嘗試領域已經嘗試突然的轉變，這是由于味覺受體（TR）不僅存在于口腔味覺簇（味蕾）中，而且也存在在沒有味覺的組織中尤其是在胃腸道黏膜中。據稱，在胃腸道黏膜中的味覺受體應答與采食后的活動有關，如識別消化管腔內的營養成分（如葡萄糖）和消化吸收的促進作用(Dyer等. 2005, Mace等， 2009)。

圖1 鈉-葡萄糖共轉運載體（紅色）和R1R2（綠色）沿著豬小腸隱窩- 絨毛軸表達

這張圖片已經被《英國營養學期刊》和相應的原始作者S. Shirazi-Beechey同意復制。原文參考：Moran AW, Al-Rammahi MA, Arora DK, Batchelor DJ, Coulter EA, Daly K, Ionescu C, Bravo D y Shirazi-Beechey. 斷奶仔豬采食人工甜味劑后，鈉-葡萄糖共轉運載體（SGL1）表達加強。2010年9月營養期刊，劍橋大學出版。

圖2，豬采食人工甜味劑后，鈉-葡萄糖共轉運載體在應答中進入豬小腸刷狀緣膜囊的初始速率。甜味劑有，瑞甜甜（43S），糖精（43Sa），新橙皮苷二氫查耳酮（43N，NHDC）或糖精NHDC（43SaN）。平均值顯著差異使用*P < 0.05, **P < 0.01, ***P < 0.001.標注。這張表被被《英國營養學期刊》和相應的原始作者S. Shirazi-Beechey同意復制。原文參考Moran等. 英國營養期刊 (2010), 104: 637-646, 劍橋大學出版。

這些相關研究建立在人用HIS似乎是不能積極增強仔豬采食量的觀點上，然而，它們可能會起到一個推動幼畜碳水化合物消化/吸收的重要作用。找到真正的助食/味道強化劑的任務仍然在進行，但是SAC,THA和/或NHDC的使用依據它們的后腸效果來判定似乎是無可非議的。

英文原文

The good taste of pigs (part I): let it be sweet

19-Apr-2011

Eugeni Roura

The search of animals for food is driven by a chemosensory code that senses the nutritional value of the available sources. Foods enter the gastrointestinal tract (GIT) through the oral cavity where its components are scrutinized and discriminated according to several chemical and physical parameters before swallowing. In hunger the chemosensory systems located in the oronasal cavity (mainly smell and taste) sense dietary nutrients and trigger or discourage further consumption. Via the GIT-hypothalamus axis peripheral sensing determines the cephalic phase of food consumption and has a direct and immediate (short term) impact on meal initiation and presumably meal size.
Simple carbohydrates, like sugars, seem to stimulate sweet taste in pigs enhancing voluntary intake. The use of sweeteners in pig diets is a common practice particularly in young animals. Among other sweeteners, non-carbohydrate high intensity sweeteners (HIS) such as saccharin (SAC), thaumatin (THA), stevioside and neohespiridine (NHDC) are widely used. Kennedy and Baldwin (1972) studied preferences to sucrose, glucose and SAC establishing thresholds that ranged from 0.005 to 0.01M for sucrose and from 0.01 to 0.03M for glucose. For both substances pigs showed consistent preferences (higher than 90%). In contrast, results for SAC were more variable and the threshold for preference did not improve sucrose and was established to be between 0.005 and 0.1M. Furthermore, preference values to SAC solutions were never higher than 90% and concentrations above 0.1 M resulted in rejection.
Danilova et al. (1999) performed electrophysiological studies in pig tongue reporting high neuronal responses to carbohydrate sweeteners such as fructose, sucrose or lactose among other mono and oligosaccharides. In preference trials sucrose showed the highest intensity of all the carbohydrates tested and their responses were very similar to sugar sensory tests in humans (Glasser et al., 2000). On the other hand pigs did not respond to human equivalent doses of HIS such as NHDC, THA, or SAC (Table 1) and the HIS combinations widely used in pig feeding such as SAC with NHDC and/or THA did not give any better response either.

Table 1. Sweetener potencies relative to sucrose (on a molar basis) in humans and pigs (adapted from Glasser et al., 2000).

		Potency relative to sucrose
		Humans	Pigs(1)
Carbohydrates	Sucrose	1,00	1,00
	D-fructose	0,50	0,50
	Lactose	0,33	0,15
	D/l-glucose	0,25	0,13
Non-Carbohydrates	Aspartame	155	< 1,00(2)
	Cyclamate (Na+ salt)	17,6	< 0,15(2)
	Neohesperidin (dihydrocalcone)	3.6	< 151(2)
	Thaumatin	2	< 1.622(2)
	Saccharin	215	3,34

(1)Sweetener potencies in pigs were measured based on double choice preference tests.
(2) Equivalent to the lowest dose tested that gave no response. The exact potency was not determined.

However, in recent years the field of sweet taste has experienced a sudden twist due to the presence of taste receptors (TR) not only in clusters in the oral cavity (taste buds) but also in non-taste tissues particularly in the mucosa of the GIT. It is believed that the TR expression in the GIT mucosa is related to post-ingestive events such as the recognition of nutrients in the lumen (i.e. glucose) and the facilitation of digestion and absorption (Dyer et al. 2005, Mace et al. 2009). Furthermore, TR in enteroendocrine cells may participate in the complex events leading to control of feed intake. For example, dietary carbohydrates and some HIS may increase glucose absorption by stimulating the T1R2 receptor in the gut mucosa which, in turn, triggers active glucose transport through the SGLT1. Porcine sweet TRs have been involved in up-regulating SGLT1 and glucose uptake after stimulation with sucrose, SAC or NHDC in piglet intestinal mucosa (Figures 1 and 2 –Moran et al. 2010-). If these findings would be confirmed we could speculate in HIS to be involved in improving glucose uptake but also to initiate an orexigenic response through GLP1, thus potentially enhancing feed intake in piglets through post-ingestive events.

Fig 1. Expression of Na++/glucose co-transporter 1 (SGLT1) in red and T1R2 in green along the crypt–villus axis of swine small intestine.

This Figure has been reproduced with permission of the British Journal of Nutrition and corresponding author of the original publication Dr. S. Shirazi-Beechey. Original reference: Moran AW, Al-Rammahi MA, Arora DK, Batchelor DJ, Coulter EA, Daly K, Ionescu C, Bravo D y Shirazi-Beechey. Expression of Na+/glucose co-transporter 1 (SGLT1) is enhanced by supplementation of the diet of weaning piglets with artificial sweeteners. 2010 Sep. Br J Nutr. Cambridge University Press.

Fig 2. Initial rates of Na+-dependent d-glucose uptake into brush-border membrane vesicles measured in swine mid-small intestine in response to feed supplementation with the artificial sweeteners, Sucram (43S), saccharin (43Sa), Neohesperidin dihydrochalcone (NHDC, 43N) or saccharin and NHDC (43SaN). Mean values were significantly different: *P < 0.05, **P < 0.01, ***P < 0.001. This Figure has been reproduced with permission of the British Journal of Nutrition and corresponding author of the original publication Dr. S. Shirazi-Beechey. Original reference: Moran et al. British Journal of Nutrition (2010), 104: 637-646, Cambridge University Press.

The relevance of these findings stands in that human HIS do not seem to be effective in increasing feed intake in piglets, however, they may play an important role in improving the efficiency of carbohydrate digestion/absorption in young animals. The task of finding true appetite/taste enhancers remains then unfinished but the use of SAC, THA and/or NHDC seems justified in the light of their post-ingestion effects.

英文來源：pig333.com